Communication method and network-side device

Abstract

The present application relates to the field of communications. Disclosed are a communication method and a network-side device. The communication method comprises: during the process of a user equipment being handed over from a source radio access network (RAN) to a target RAN, a first core network element sending a first message to the target RAN, wherein the first message is configured to request handover of the user equipment to the target RAN, and the first core network element is configured for session management.

Description

Communication methods and network-side equipment

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 202411973216.6, filed with the Chinese Patent Office on December 30, 2024, entitled "Communication Method and Network Side Device", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application belongs to the field of communication technology, specifically relating to a communication method and a network-side device. Background Technology

[0004] In related technologies, during the handover process of a user equipment (UE) through its radio access network (RAN), the Access & Mobility Management Function (AMF) forwards handover-related information between the RAN and the Session Management Function (SMF), as well as between the UE and the SMF. Because the transmission path for this handover-related information is relatively long, it leads to a series of problems, including low transmission efficiency, high AMF load, and high coupling between the AMF and SMF, making independent upgrades difficult. Summary of the Invention

[0005] This application provides a communication method and a network-side device that can solve at least one problem existing in current wireless access network handover schemes.

[0006] Firstly, a communication method is provided, the method comprising:

[0007] During the process of a terminal switching from the source radio access network (RAN) to the target RAN, a first core network element sends a first message to the target RAN. The first message is used to request the terminal to switch to the target RAN, and the first core network element is used for session management.

[0008] Secondly, a communication method is provided, the method comprising:

[0009] During the process of a terminal switching from the source radio access network (RAN) to the target RAN, the first core network element receives a fifth message sent by the target RAN. The fifth message is used to request the terminal to switch to the target RAN, and the first core network element is used for session management.

[0010] Thirdly, a communication method is provided, the method comprising:

[0011] When a terminal switches from a source radio access network (RAN) to a target RAN, a first core network element receives a tenth message sent by the target RAN. The tenth message is used to instruct the first core network element to control a third core network element to switch the user plane path of the terminal's session from the source RAN to the target RAN. The first core network element is used for session management.

[0012] Fourthly, a communication method is provided, which includes:

[0013] During the process of a terminal switching from a source radio access network (RAN) to a target RAN, the target RAN receives a first message sent by a first core network element. The first message is used to request the terminal to be switched to the target RAN. The first core network element is used for session management.

[0014] Fifthly, a communication method is provided, the method comprising:

[0015] During the process of a terminal switching from the source radio access network (RAN) to the target RAN, the target RAN sends a fifth message to the first core network element. The fifth message is used to request the terminal to be switched to the target RAN. The first core network element is used for session management.

[0016] Sixthly, a communication method is provided, the method comprising:

[0017] When a terminal switches from a source radio access network (RAN) to a target RAN, the target RAN sends a tenth message to the first core network element. The tenth message is used to instruct the first core network element to control a third core network element to switch the user plane path of the terminal's session from the source RAN to the target RAN. The first core network element is used for session management.

[0018] Seventhly, a communication method is provided, the method comprising:

[0019] During the process of a terminal switching from the source radio access network (RAN) to the target RAN, the second core network element sends an eighth message to the target RAN. The eighth message is used to trigger the target RAN to receive a first message sent by the first core network element. The first message is used to request the terminal to switch to the target RAN. The first core network element is used for session management.

[0020] Eighthly, a communication method is provided, the method comprising:

[0021] During the process of a terminal switching from the source radio access network (RAN) to the target RAN, the second core network element sends an eleventh message to the target RAN. The eleventh message is used to trigger the target RAN to send a fifth message to the first core network element. The fifth message is used to request the terminal to switch to the target RAN. The first core network element is used for session management.

[0022] Ninthly, a communication method is provided, the method comprising:

[0023] When a terminal switches from the source radio access network (RAN) to the target RAN, the second core network element receives a ninth message sent by the target RAN, wherein the ninth message is used to request that the user plane path of the terminal's session be switched from the source RAN to the target RAN.

[0024] Tenthly, a communication method is provided, the method comprising:

[0025] During the process of a terminal switching from a source radio access network (RAN) to a target RAN, the source RAN receives a third message sent by a first core network element. The third message is used to instruct the source RAN to forward data to the target RAN through an indirect forwarding tunnel. The indirect forwarding tunnel refers to the data transmission tunnel from the source RAN to the third core network element and then from the third core network element to the target RAN. The first core network element is used for session management.

[0026] Eleventhly, a communication device is provided, applied to a first core network element, the device comprising:

[0027] The sending module is used to send a first message to the target RAN during the process of a terminal switching from the source radio access network RAN ​​to the target RAN, wherein the first message is used to request the terminal to switch to the target RAN, and the first core network element is used for session management.

[0028] In a twelfth aspect, a communication device is provided, applied to a first core network element, the device comprising:

[0029] The receiving module is configured to receive a fifth message sent by the target RAN during the process of the terminal switching from the source radio access network RAN ​​to the target RAN, wherein the fifth message is used to request the terminal to switch to the target RAN, and the first core network element is used for session management.

[0030] In a thirteenth aspect, a communication device is provided, applied to a first core network element, the device comprising:

[0031] The receiving module is configured to receive a tenth message sent by the target RAN when the terminal switches from the source radio access network RAN ​​to the target RAN. The tenth message is configured to instruct the first core network element to control the third core network element to switch the user plane path of the terminal's session from the source RAN to the target RAN. The first core network element is used for session management.

[0032] In a fourteenth aspect, a communication apparatus is provided for use in a target radio access network (RAN), the apparatus comprising:

[0033] The receiving module is used to receive a first message sent by a first core network element during the process of a terminal switching from a source RAN to the target RAN. The first message is used to request the terminal to be switched to the target RAN. The first core network element is used for session management.

[0034] In a fifteenth aspect, a communication apparatus is provided for use in a target radio access network (RAN), the apparatus comprising:

[0035] The sending module is used to send a fifth message to a first core network element during the process of a terminal switching from a source RAN to the target RAN. The fifth message is used to request the terminal to switch to the target RAN. The first core network element is used for session management.

[0036] In a sixteenth aspect, a communication apparatus is provided for use in a target radio access network (RAN), the apparatus comprising:

[0037] The sending module sends a tenth message to the first core network element when the terminal switches from the source RAN to the target RAN. The tenth message is used to instruct the first core network element to control the third core network element to switch the user plane path of the terminal's session from the source RAN to the target RAN. The first core network element is used for session management.

[0038] In a seventeenth aspect, a communication device is provided for use in a second core network element, the device comprising:

[0039] The sending module is used to send an eighth message to the target RAN during the process of a terminal switching from a source radio access network (RAN) to a target RAN. The eighth message is used to trigger the target RAN to receive a first message sent by a first core network element. The first message is used to request the terminal to switch to the target RAN. The first core network element is used for session management.

[0040] Eighteenthly, a communication device is provided for use in a second core network element, the device comprising:

[0041] The sending module is used to send an eleventh message to the target RAN during the process of the terminal switching from the source radio access network RAN ​​to the target RAN. The eleventh message is used to trigger the target RAN to send a fifth message to the first core network element. The fifth message is used to request the terminal to switch to the target RAN. The first core network element is used for session management.

[0042] In a nineteenth aspect, a communication device is provided for use in a second core network element, the device comprising:

[0043] The receiving module is configured to receive a ninth message sent by the target RAN when the terminal switches from the source radio access network RAN ​​to the target RAN, wherein the ninth message is used to request that the user plane path of the terminal's session be switched from the source RAN to the target RAN.

[0044] In a twentieth aspect, a communication apparatus is provided for use in a source radio access network (RAN), the apparatus comprising:

[0045] The receiving module is used to receive a third message sent by a first core network element during the process of a terminal switching from the source RAN to the target RAN. The third message is used to instruct the source RAN to forward data to the target RAN through an indirect forwarding tunnel. The indirect forwarding tunnel refers to the data transmission tunnel from the source RAN to the third core network element and then from the third core network element to the target RAN. The first core network element is used for session management.

[0046] In a twenty-first aspect, a communication device is provided, the device being configured to perform the steps of the method as described in any one of the first to tenth aspects.

[0047] In a twenty-second aspect, a network-side device is provided, the network-side device including a processor and a memory, the memory storing a program or instructions executable on the processor, the program or instructions, when executed by the processor, implementing the steps of the method as described in any one of the first to tenth aspects.

[0048] In a twenty-third aspect, a readable storage medium is provided, on which a program or instructions are stored, which, when executed by a processor, implement the steps of the method as described in any one of the first to tenth aspects.

[0049] In a twentieth aspect, a wireless communication system is provided, comprising: a first core network device, a target radio access network (RAN), a second core network device, and a source RAN, wherein the first core network device is configured to perform the steps of the method described in the first aspect, the target RAN is configured to perform the steps of the method described in the fourth aspect, the second core network device is configured to perform the steps of the method described in the seventh aspect, and the source RAN is configured to perform the steps of the method described in the tenth aspect.

[0050] In a twentieth aspect, a wireless communication system is provided, comprising: a first core network device, a target radio access network (RAN), and a second core network device, wherein the first core network device is configured to perform the steps of the method described in the second aspect, the target RAN is configured to perform the steps of the method described in the fifth aspect, and the second core network device is configured to perform the steps of the method described in the eighth aspect.

[0051] In a twentieth aspect, a wireless communication system is provided, comprising: a first core network device, a target radio access network (RAN), and a second core network device, wherein the first core network device is configured to perform the steps of the method described in the third aspect, the target RAN is configured to perform the steps of the method described in the sixth aspect, and the second core network device is configured to perform the steps of the method described in the ninth aspect.

[0052] In a twenty-seventh aspect, a chip is provided, the chip including a processor and a communication interface coupled to the processor, the processor being configured to run programs or instructions to implement the method as described in any one of the first to tenth aspects.

[0053] In a twenty-eighth aspect, a computer program / program product is provided, the computer program / program product being stored in a storage medium, the computer program / program product being executed by at least one processor to implement the steps of the two methods as described in any one of the first to tenth aspects.

[0054] In this embodiment, since the target RAN can directly send a request for RAN handover to the first core network element used for session management, or directly receive a request for RAN handover from the first core network element without the need for forwarding by other core network elements, it can achieve the effects of shortening the transmission path of handover-related information, improving the transmission efficiency of handover-related information, reducing the load of other core network elements, and decoupling the second core network element from the first core network element. Attached Figure Description

[0055] Figure 1 is a block diagram of a wireless communication system applicable to an embodiment of this application.

[0056] Figure 2A is a schematic diagram of a network architecture provided in an embodiment of this application.

[0057] Figure 2B is a schematic diagram of a network architecture provided in another embodiment of this application.

[0058] Figure 3 is a flowchart illustrating a communication method proposed in an embodiment of this application.

[0059] Figure 4 is a flowchart illustrating a communication method proposed in an embodiment of this application.

[0060] Figure 5 is a flowchart illustrating a communication method proposed in an embodiment of this application.

[0061] Figure 6 is a flowchart illustrating a communication method proposed in an embodiment of this application.

[0062] Figure 7 is a flowchart illustrating a communication method proposed in an embodiment of this application.

[0063] Figure 8 is a flowchart illustrating a communication method proposed in another embodiment of this application.

[0064] Figure 9 is a flowchart illustrating a communication method according to another embodiment of this application.

[0065] Figure 10 is a flowchart illustrating a communication method according to another embodiment of this application.

[0066] Figure 11 is a flowchart illustrating a communication method according to another embodiment of this application.

[0067] Figure 12 is a flowchart illustrating a communication method according to another embodiment of this application.

[0068] Figure 13 is a flowchart illustrating a communication method according to another embodiment of this application.

[0069] Figure 14 is a flowchart illustrating a communication method according to another embodiment of this application.

[0070] Figure 15 is a flowchart illustrating a communication method according to another embodiment of this application.

[0071] Figure 16 is a schematic diagram of the structure of a communication device according to an embodiment of this application.

[0072] Figure 17 is a schematic diagram of the structure of a communication device according to an embodiment of this application.

[0073] Figure 18 is a schematic diagram of the structure of a communication device according to an embodiment of this application.

[0074] Figure 19 is a schematic diagram of the structure of a communication device according to an embodiment of this application.

[0075] Figure 20 is a schematic diagram of the structure of a communication device according to another embodiment of this application.

[0076] Figure 21 is a schematic diagram of the structure of a communication device according to another embodiment of this application.

[0077] Figure 22 is a schematic diagram of the structure of a communication device according to another embodiment of this application.

[0078] Figure 23 is a schematic diagram of the structure of a communication device according to another embodiment of this application.

[0079] Figure 24 is a schematic diagram of the structure of a communication device according to another embodiment of this application.

[0080] Figure 25 is a schematic diagram of the structure of a communication device according to another embodiment of this application.

[0081] Figure 26 is a schematic diagram of the structure of a communication device proposed in an embodiment of this application.

[0082] Figure 27 is a schematic diagram of the structure of a terminal proposed in an embodiment of this application.

[0083] Figure 28 is a schematic diagram of the structure of a network-side device proposed in an embodiment of this application.

[0084] Figure 29 is a schematic diagram of the structure of a network-side device proposed in an embodiment of this application. Detailed Implementation

[0085] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0086] The terms "first," "second," etc., used in this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first" and "second" are generally of the same class, not limited in number; for example, the first object can be one or more. Furthermore, "or" in this application indicates at least one of the connected objects. For example, the scope of protection for "A or B" covers at least three scenarios: Scenario 1: including A but not B; Scenario 2: including B but not A; Scenario 3: including both A and B. In addition, the terms "A and / or B," "at least one of A and B," and "at least one of A or B" also cover at least the above three scenarios. The character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0087] The term "instruction" in this application can be either a direct instruction (or explicit instruction) or an indirect instruction (or implicit instruction). A direct instruction can be understood as the sender explicitly informing the receiver of specific information, the required operation, or the requested result in the instruction sent. An indirect instruction can be understood as the receiver determining the corresponding information based on the instruction sent by the sender, or making a judgment and determining the required operation or requested result based on the judgment result.

[0088] It is worth noting that the technologies described in this application are not limited to Long Term Evolution (LTE) / LTE-Advanced (LTE-A) systems, but can also be used in other wireless communication systems, such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single-carrier Frequency-Division Multiple Access (SC-FDMA), or other systems. The terms "system" and "network" in this application are often used interchangeably, and the described technologies can be used in the systems and radio technologies mentioned above, as well as in other systems and radio technologies. The following description describes New Radio (NR) systems for illustrative purposes, and the term NR is used in most of the following description; however, these technologies can also be applied to systems other than NR systems, such as 6th Generation (6G) communication systems.

[0089] Figure 1 shows a block diagram of a wireless communication system applicable to an embodiment of this application. The wireless communication system includes a terminal 11 and a network-side device 12. The terminal 11 can also be referred to as User Equipment (UE), and can be a mobile phone, tablet computer, laptop computer, notebook computer, personal digital assistant (PDA), handheld computer, netbook, ultra-mobile personal computer (UMPC), mobile internet device (MID), augmented reality (AR), virtual reality (VR) device, robot, wearable device, flight vehicle, vehicle user equipment (VUE), shipboard equipment, pedestrian user equipment (PUE), smart home (home devices with wireless communication capabilities, such as refrigerators, televisions, washing machines, or furniture), game console, personal computer (PC), ATM, or self-service machine, etc. Wearable devices include: smartwatches, smart bracelets, smart headphones, smart glasses, smart jewelry (smart bracelets, smart chains, smart rings, smart necklaces, smart anklets, smart anklets, etc.), smart wristbands, smart clothing, etc. Among these, in-vehicle devices can also be referred to as in-vehicle terminals, in-vehicle controllers, in-vehicle modules, in-vehicle components, in-vehicle chips, or in-vehicle units, etc. It should be noted that the specific type of terminal 11 is not limited in this application embodiment. Network-side equipment 12 may include access network equipment or core network equipment, wherein access network equipment may also be referred to as Radio Access Network (RAN) equipment, radio access network function, or radio access network unit. Access network equipment may include base stations, Wireless Local Area Network (WLAN) access points (APs), or Wireless Fidelity (WiFi) nodes, etc.Among them, base stations can be referred to as Node B (NB), Evolved Node B (eNB), Next Generation Node B (gNB), New Radio Node B (NR Node B), Access Point, Relay Base Station (RBS), Serving Base Station (SBS), Base Transceiver Station (BTS), Radio Base Station, Radio Transceiver, Basic Service Set (BSS), Extended Service Set (ESS), Home Node B (HNB), Home Evolved Node B, Transmit / Receive Point (TRP), Non-Terrestrial Network (NTN) equipment (such as satellite or high altitude platform stations). The term "base station" can be any suitable term in the field, such as "station" or any other appropriate term in the relevant field, as long as the same technical effect is achieved. The term "base station" is not limited to specific technical terms. It should be noted that the embodiments of this application only use the base station in the NR system as an example for introduction, and do not limit the specific type of base station.

[0090] Core network equipment, also known as core network nodes, core network functions, or core network elements, includes, but is not limited to, at least one of the following: Mobility Management Entity (MME), Access and Mobility Management Function (AMF), Session Management Function (SMF), User Plane Function (UPF), Policy Control Function (PCF), Policy and Charging Rules Function (PCRF), Edge Application Server Discovery Function (EASDF), Unified Data Management (UDM), Unified Data Repository (UDR), Home Subscriber Server (HSS), Centralized network configuration (CNC), Network Repository Function (NRF), Network Exposure Function (NEF), Local NEF (L-NEF), and Binding Support. Functions include BSF, Application Function (AF), Location Management Function (LMF), Gateway Mobile Location Centre (GMLC), Network Data Analytics Function (NWDAF), and Non-Terrestrial Network (NTN) equipment (such as satellite or high altitude platform station).It should be noted that the embodiments of this application only use the core network equipment in the NR system as an example for introduction, and do not limit the specific type of core network equipment. If the name of the core network equipment mentioned in the embodiments of this application changes in subsequent protocol versions (e.g., 6G), it is also within the scope of protection of this application.

[0091] Optionally, the core network equipment can be implemented by one or more functional modules in a single device, or by multiple devices working together; this application does not specifically limit this. It is understood that the aforementioned functional modules can be network elements in hardware devices, software functional modules running on dedicated hardware, or virtualized functional modules instantiated on a platform (e.g., a cloud platform).

[0092] To address at least one problem with current wireless access network handover schemes, this application proposes a communication method. This proposed communication method is applicable both to handover within 5G / 6G systems and to handover between 5G and 6G systems.

[0093] The communication method proposed in this application can be applied to a network architecture with N2 interface service between the Radio Access Network (RAN) and the second core network element. In this network architecture, the RAN, the second core network element, and the first core network element can communicate directly based on the Service Based Interface (SBI). The first core network element is used for session management, for example, it can be a Session Management Function (SMF). The second core network element is used for access and mobility management, for example, it can be an Access and Mobility Management Function (AMF). The following description primarily uses the first core network element as the SMF and the second core network element as the AMF as examples.

[0094] In some embodiments, the communication method proposed in this application can be applied to a network architecture modified from the network architecture shown in Figure 2A, such as a network architecture after adding a reference interface between the RAN and SMF in the network architecture shown in Figure 2A.

[0095] Figure 2A illustrates the 5G Service Based Architecture (SBA). In this architecture, the core network's control plane elements (AMF, SMF, Policy Control Function (PCF), Unified Data Management (UDM), and Authentication Server Function (AUSF) communicate via the SBI. The RAN communicates with the AMF through the reference point interface N2. The N2 interface is also used to transmit Non-Access Stratum (NAS) messages between the UE and AMF on the N1 interface. In related technologies, the AMF forwards session management-related messages between the RAN and SMF, and between the UE and SMF, via the N2 interface. Examples include messages related to Protocol Data Unit (PDU) session modifications during handover. If the RANs support the Xn interface, the source RAN and target RAN can transmit handover requests, handover responses, and perform direct data forwarding via the Xn interface. If the RANs do not support the Xn interface, the source RAN and target RAN cannot communicate directly and must transmit handover-related messages via the N2 interface. Both the source RAN and the target RAN communicate with the AMF (which can be the same AMF or different AMFs) through the N2 interface. The AMF forwards handover-related messages between the UE, source RAN, target RAN, and SMF. When multiple SMF-controlled PDU sessions are modified, the AMF monitors the completion of handover responses for each SMF-controlled PDU session modification before instructing the source RAN to forward data to the target RAN via an indirect forwarding path. This allows the target RAN to send data forwarded from the source RAN to the UE after a successful handover to the target RAN. However, this technology has the following drawbacks during handover: 1) The forwarding of handover-related messages between the RAN and SMF, and between the UE and SMF, by the AMF results in low transmission efficiency and high AMF load due to path detours. This also leads to high coupling between the AMF and SMF, making independent upgrades difficult. 2) The AMF can only trigger the source RAN to forward data to the target RAN via an indirect path after monitoring the completion of handover responses for one or more SMF-controlled PDU sessions, resulting in significant service interruption latency during handover.

[0096] In other embodiments, the communication method proposed in this application can be applied to the network architecture shown in Figure 2B. As shown in Figure 2B, the N2 interface between the RAN and AMF is modified to the service interface in the service-oriented network architecture of Figure 2B, enabling the RAN to communicate with the AMF and SMF via SBI.

[0097] The communication method provided in this application will be described in detail below with reference to the accompanying drawings and through some embodiments and application scenarios.

[0098] As shown in Figure 3, one embodiment of this application provides a communication method that may include:

[0099] Step 301: During the process of the terminal switching from the source radio access network (RAN) to the target RAN, the first core network element sends a first message to the target RAN, wherein the first message is used to request the terminal to switch to the target RAN, and the first core network element is used for session management.

[0100] In some embodiments, the first core network element may be an SMF.

[0101] In some embodiments, the first message may carry at least one of the following information:

[0102] The first terminal identifier is an identifier assigned to the terminal by the source RAN (S-RAN). The first terminal identifier can be represented as S-RAN UE ID.

[0103] The terminal's session ID, as an example, can be a PDU session, and the terminal's session ID can be a PDU session ID;

[0104] The Tunnel Endpoint Identifier (TEID) information of the third core network element is used for user plane management. For example, the third core network element can be a UPF.

[0105] As an example, in step 301, the first core network element can send a handover request message (e.g., Nran_HandoverRequest) to the target RAN as the first message. The handover request message indicates the PDU session ID and UPF Tunnel Endpoint Identifier (TEID) information of the UE to be handed over. Specifically, the handover request message may carry the first terminal identifier (e.g., S-RAN UE ID), PDU session ID, UPF Tunnel Endpoint Identifier (TEID), and session management information list SM N2.

[0106] The communication method proposed in the embodiment shown in Figure 3 can directly send the first message for RAN handover to the target RAN because the first core network element used for session management can do so without the need for the second core network element to forward the RAN handover related information. Therefore, it can solve a series of problems in related technologies, such as low transmission efficiency of handover related information, high AMF load, and high coupling between AMF and SMF making independent upgrades difficult, due to the long transmission path of handover related information. This achieves the effects of shortening the transmission path of handover related information, improving the transmission efficiency of handover related information, reducing the load of other core network elements, and decoupling the second core network element from the first core network element.

[0107] Optionally, the method shown in Figure 3 may further include: the first core network element receiving a first acknowledgment message sent by the target RAN in response to the first message.

[0108] The first confirmation message may carry at least one of the following information:

[0109] The second terminal identifier is the identifier assigned to the terminal by the target RAN (T-RAN). The second terminal identifier can be represented as the T-RAN UE ID.

[0110] The Tunnel Endpoint Identifier (TEID) information of the target RAN (T-RAN) is used by the first core network element and the third core network element to modify the session of the terminal. The TEID information of the target RAN may include the TEID of the target RAN, which may be represented as T-RAN TEID.

[0111] For example, the target RAN can send a handover request confirmation message (e.g., Nran_HandoverRequest_Ack) to the SMF carrying a first confirmation message. This handover request confirmation message contains the T-RAN UE ID, T-RAN TEID, PDU session ID information for successful and failed handovers, etc.

[0112] Optionally, if the terminal's session is a PDU session, the first core network element and the third core network element of the target RAN perform N4 session modification on the TEID information of the terminal. For example, the SMF and UPF of the target RAN perform N4 session modification.

[0113] Similarly, since the target RAN can directly send the first acknowledgment message for the first message to the first core network element used for session management, without the need for the second core network element to forward RAN handover related information, it can solve a series of problems in related technologies, such as low transmission efficiency of handover related information, high load on the second core network element, and high coupling between the second and first core network elements, which makes it difficult to upgrade independently. This achieves the effects of shortening the transmission path of handover related information, improving the transmission efficiency of handover related information, reducing the load on other core network elements, and decoupling the second and first core network elements.

[0114] Optionally, before step 301, the method shown in Figure 3 may further include:

[0115] The first core network element receives a second message sent by the second core network element, wherein the second message is used to instruct the first core network element that the terminal needs to switch from the source RAN to the target RAN.

[0116] The second message carries at least one of the following information:

[0117] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0118] The terminal corresponds to the user's permanent identifier (SUPI).

[0119] The ID of the target RAN can be represented as target ID.

[0120] For example, the SMF can receive a second message sent by the AMF—a handover notification message (e.g., Nsmf_Handover_Notification). This handover notification message indicates to the SMF that the terminal needs to hand over from the source RAN to the target RAN. The handover notification message may include a first terminal identifier (e.g., S-RAN UE ID), the SUPI corresponding to the terminal, and the ID of the target RAN (e.g., target ID).

[0121] Optionally, before step 301, the method shown in Figure 3 may further include:

[0122] The first core network element sends a second confirmation message to the second core network element in response to the second message. The second confirmation message carries the user permanent identifier SUPI corresponding to the terminal.

[0123] For example, the SMF can send a handover notification confirmation message (e.g., Nsmf_Handover_Notification_Ack) to the AMF, which carries a second confirmation message containing the SUPI corresponding to the terminal.

[0124] Optionally, the first core network element can also select a third core network element based on the second message, for example, the SMF selects the UPF. Optionally, in this embodiment, the UPF remains unchanged before and after the handover.

[0125] Optionally, the first core network element can also perform session modification of the terminal with the third core network element. For example, the SMF can perform N4 session modification with the UPF based on the T-RAN TEID.

[0126] Optionally, after the first core network element receives the first acknowledgment message for the first message sent by the target RAN, the method shown in FIG3 may further include:

[0127] The first core network element sends a third message to the source RAN, wherein the third message instructs the source RAN to forward data to the target RAN through an indirect forwarding tunnel. The indirect forwarding tunnel refers to a data transmission tunnel from the source RAN to the third core network element, and then from the third core network element to the target RAN. It should be noted that the network elements included in the indirect forwarding tunnel may include only the source RAN, the target RAN, and the third core network element; other network elements may also be included besides these three.

[0128] The third message may carry at least one of the following information:

[0129] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0130] The terminal's session ID;

[0131] The Tunnel Endpoint Identifier (TEID) information of the third core network element. When the third core network element is a UPF, the TEID information of the third core network element may include the TEID of the third core network element, and the Tunnel Endpoint Identifier (TEID) of the third core network element may be represented as UPF TEID.

[0132] For example, the SMF can send a handover indication message (e.g., Nran_HandoverIndication) as a third message to the source RAN. This handover indication message indicates that the source RAN can begin data forwarding through an indirect forwarding tunnel. The handover indication message may carry a first terminal identifier (e.g., S-RAN UE ID), a PDU session ID, and the UPF's tunnel endpoint identifier (TEID) information (e.g., UPF TEID). It is understood that since the handover indication message does not need to be forwarded through the AMF, a series of problems caused by the circuitous handover path in related technologies can be solved.

[0133] Accordingly, the source RAN can perform data forwarding for the Protocol Data Unit (PDU) session corresponding to the session ID of the terminal under the first core network element. It should be noted that, in this embodiment, the source RAN does not need to wait for the handover response of all sessions to be completed before it can start data forwarding, and can perform data forwarding in parallel for the data of sessions controlled by different first core network elements, which further reduces the service interruption latency during handover.

[0134] Optionally, the method shown in Figure 3 may further include: the first core network element receiving a fourth message sent by the target RAN, the fourth message being used to notify the terminal that the handover from the source RAN to the target RAN has been completed. For example, after the handover is completed, the target RAN may send a handover notification (e.g., Nsmf_Handover_Notify) as the fourth message to the first core network element, the handover notification being used to indicate to the first core network element that the handover has been completed.

[0135] The communication method proposed in the embodiment shown in Figure 3 can directly interact with the target RAN regarding RAN handover information because the first core network element used for session management can do so without the need for the second core network element to forward the RAN handover information. Therefore, it can solve a series of problems in related technologies, such as low transmission efficiency of handover information, high load on the second core network element, and high coupling between the second and first core network elements, which makes independent upgrades difficult due to the long transmission path of handover information. This achieves the effects of shortening the transmission path of handover information, improving the transmission efficiency of handover information, reducing the load on other core network elements, and decoupling the second and first core network elements.

[0136] As shown in Figure 4, a communication method provided in this application embodiment may include:

[0137] Step 401: During the process of the terminal switching from the source RAN to the target RAN, the target RAN receives a first message sent by the first core network element. The first message is used to request the terminal to be switched to the target RAN. The first core network element is used for session management.

[0138] The first message may carry at least one of the following information:

[0139] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0140] The terminal's session ID;

[0141] The Tunnel Endpoint Identifier (TEID) information of the third core network element.

[0142] Optionally, after step 401, the method shown in FIG4 may further include: the target RAN sending a first confirmation message for the first message to the first core network element.

[0143] The first confirmation message carries at least one of the following information:

[0144] The second terminal identifier is an identifier assigned to the terminal by the target RAN;

[0145] The Tunnel Endpoint Identifier (TEID) information of the target RAN is used by the first core network element and the third core network element to modify the session of the terminal.

[0146] Optionally, before step 401, the method shown in Figure 4 may further include: the target RAN receiving the eighth message sent by the second core network element.

[0147] The eighth message carries at least one of the following information:

[0148] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0149] UE context information related to mobility management;

[0150] The session ID of the terminal is the session information of the terminal under the first core network element.

[0151] For example, the target RAN can receive a handover UE context notification message (e.g., Nran_Handover_UEContext_Notify) sent by the AMF as the eighth message. The handover UE context notification message may carry a first terminal identifier (e.g., S-RAN UE ID), a UE mobility management information list N2 MM, and a PDU session ID, wherein the PDU session ID is used to indicate the PDU session information of the terminal under the SMF.

[0152] Optionally, before step 401, the method shown in FIG4 may further include: the target RAN sending a sixth confirmation message for the eighth message to the second core network element, wherein the sixth confirmation message carries a second terminal identifier, the second terminal identifier being an identifier assigned by the target RAN to the terminal.

[0153] For example, the target RAN can assign a second terminal identifier (e.g., T-RAN UE ID) to the terminal and send a handover_UE context notification confirmation message (e.g., Nran_Handover_UEContext_Notify_ACK) carrying the second terminal identifier to the AMF, that is, send the sixth confirmation message for the eighth message.

[0154] Optionally, after step 401, the method shown in FIG4 may further include: the target RAN sending a fifteenth message to the second core network element, wherein the fifteenth message is used by the second core network element to instruct the source RAN to forward data to the target RAN through an indirect forwarding tunnel, wherein the indirect forwarding tunnel refers to the data transmission tunnel from the source RAN to the third core network element, and then from the third core network element to the target RAN.

[0155] The fifteenth message may carry at least one of the following information:

[0156] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0157] The terminal's session ID;

[0158] The Tunnel Endpoint Identifier (TEID) information of the third core network element.

[0159] For example, the target RAN can send a handover indication (e.g., Nran_HandoverIndication) message to the AMF as the fifteenth message, to instruct the AMF to send a handover indication (e.g., Nran_HandoverIndication) message to the source RAN, which triggers the source RAN to start data forwarding through the indirect forwarding tunnel.

[0160] Accordingly, the source RAN can perform data forwarding for the PDU session corresponding to the session ID of the terminal under the first core network element. It should be noted that, in this embodiment, the source RAN does not need to wait for the handover response of all sessions to be completed before it can start data forwarding, and can perform data forwarding in parallel for the data of sessions controlled by different first core network elements, which further reduces the service interruption latency during handover.

[0161] Optionally, the method shown in Figure 4 may further include:

[0162] The target RAN monitors the handover response information of each session of the terminal;

[0163] When the target RAN determines that the handover of each session is complete based on the handover response information of each session, it sends a fourteenth message to the second core network element, wherein the fourteenth message is used to instruct the second core network element to send a handover command about the terminal to the source RAN.

[0164] For example, the target RAN monitors the handover response status of each PDU session ID. Further, after determining that the handover of each PDU session is complete based on the handover response information of each PDU session, the target RAN sends a handover command (e.g., Namf_Handover_Command) to the AMF, which contains a transparent container from the target RAN to the source RAN, requesting the AMF to send a handover command (e.g., Nran_Handover_Command) to the source RAN.

[0165] Optionally, the method shown in Figure 4 may further include: the target RAN sending a seventeenth message to the second core network element, the seventeenth message being used to notify the terminal that the handover from the source RAN to the target RAN has been completed. For example, the target RAN sends a handover notification (e.g., Namf_Handover_Notify) to the AMF as the seventeenth message, the handover notification being used to indicate to the AMF that the terminal has completed the handover.

[0166] Optionally, the method shown in Figure 4 may further include: the target RAN sending a seventh message to the first core network element, the seventh message being used to notify the terminal that the handover from the source RAN to the target RAN has been completed. For example, the target RAN sends a handover notification (e.g., Namf_Handover_Notify) to the SMF, indicating to the SMF that the terminal has completed the handover.

[0167] The communication method proposed in the embodiment shown in Figure 4 can directly interact with the first core network element used for session management to exchange RAN handover related information, without the need for the second core network element to forward the RAN handover related information. Therefore, it can solve a series of problems in related technologies, such as low transmission efficiency of handover related information, high load on the second core network element, and high coupling between the second core network element and the first core network element, which makes it difficult to upgrade independently due to the long transmission path of handover related information. Thus, it achieves the effects of shortening the transmission path of handover related information, improving the transmission efficiency of handover related information, reducing the load on other core network elements, and decoupling the second core network element from the first core network element.

[0168] As shown in Figure 5, a communication method provided in this application embodiment may include:

[0169] Step 501: During the process of the terminal switching from the source RAN to the target RAN, the second core network element sends an eighth message to the target RAN. The eighth message is used to trigger the target RAN to receive a first message sent by the first core network element. The first message is used to request the terminal to switch to the target RAN. The first core network element is used for session management.

[0170] The eighth message carries at least one of the following information:

[0171] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0172] UE context information related to mobility management;

[0173] The session ID of the terminal is the session information of the terminal under the first core network element.

[0174] For example, the AMF can send a handover UE context notification message (e.g., Nran_Handover_UEContext_Notify) to the target RAN as the eighth message. This handover UE context notification message may carry a first terminal identifier (e.g., S-RAN UE ID), a UE mobility management information list N2 MM, and a PDU session ID, where the PDU session ID is used to indicate the PDU session information of the terminal under this SMF.

[0175] Optionally, the method shown in Figure 5 may further include: the second core network element receiving a sixth confirmation message for the eighth message sent by the target RAN, wherein the sixth confirmation message carries a second terminal identifier, the second terminal identifier being an identifier assigned to the terminal by the target RAN.

[0176] For example, the AMF can receive a handover_UEContext_Notify_ACK message (e.g., Nran_Handover_UEContext_Notify_ACK) carrying a second terminal identifier sent by the target RAN, which is the sixth confirmation message for the eighth message.

[0177] Optionally, before step 501, the terminal sends a measurement report to the source RAN, the source RAN makes a handover decision, and the source RAN assigns a first terminal identifier (e.g., S-RAN UE ID) to the terminal. Accordingly, the method shown in Figure 5 may further include: the second core network element receiving a sixteenth message sent by the source RAN, wherein the sixteenth message is used to indicate that the terminal needs to hand over from the source RAN to the target RAN.

[0178] The sixteenth message carries at least one of the following information:

[0179] In this embodiment, the first terminal identifier is used to associate the terminal with the second core network element and the corresponding session ID. The first terminal identifier can be represented as the S-RAN UE ID.

[0180] Target RAN ID;

[0181] The terminal's session ID.

[0182] Optionally, the method shown in Figure 5 may further include: the second core network element selecting the first core network element. In this embodiment, the first core network element may remain unchanged before and after the switch.

[0183] Optionally, before step 501, the method shown in FIG5 may further include: the second core network element sending a second message to the first core network element, wherein the second message is used to instruct the first core network element that the terminal needs to switch from the source RAN to the target RAN.

[0184] The second message carries at least one of the following information:

[0185] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0186] The user permanent identifier SUPI corresponding to the terminal;

[0187] The ID of the target RAN.

[0188] For example, the AMF can send a handover notification message (e.g., Nsmf_Handover_Notification) to the SMF as a second message. This handover notification message indicates to the SMF that the terminal needs to hand over from the source RAN to the target RAN. The handover notification message may include a first terminal identifier (e.g., S-RAN UE ID), the SUPI corresponding to the terminal, and the ID of the target RAN.

[0189] Optionally, before step 501, the method shown in FIG5 may further include: the second core network element receiving a second confirmation message sent by the first core network element for the second message, wherein the second confirmation message carries the user permanent identifier SUPI corresponding to the terminal.

[0190] For example, the AMF can receive a handover notification confirmation message (e.g., Nsmf_Handover_Notification_Ack) sent by the SMF, which carries a second confirmation message containing the SUPI corresponding to the terminal.

[0191] Optionally, after step 501, the method shown in FIG5 may further include: the second core network element receiving a fourteenth message sent by the target RAN, wherein the fourteenth message is used to instruct the second core network element to send a handover command about the terminal to the source RAN.

[0192] Optionally, after step 501, the method shown in FIG5 may further include: the second core network element receiving the fifteenth message sent by the target RAN, wherein the fifteenth message is used by the second core network element to instruct the source RAN to forward data to the target RAN through an indirect forwarding tunnel, wherein the indirect forwarding tunnel refers to the data transmission tunnel from the source RAN to the third core network element, and then from the third core network element to the target RAN.

[0193] The fifteenth message may carry at least one of the following information:

[0194] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0195] The terminal's session ID;

[0196] The Tunnel Endpoint Identifier (TEID) information of the third core network element.

[0197] For example, the target RAN can send a handover indication (e.g., Nran_HandoverIndication) message to the AMF as the fifteenth message, to instruct the AMF to send a handover indication (e.g., Nran_HandoverIndication) message to the source RAN, which triggers the source RAN to start data forwarding through the indirect forwarding tunnel.

[0198] Accordingly, the source RAN can perform data forwarding for the PDU session corresponding to the session ID of the terminal under the first core network element. It should be noted that, in this embodiment, the source RAN does not need to wait for the handover response of all sessions to be completed before it can start data forwarding, and can perform data forwarding in parallel for the data of sessions controlled by different first core network elements, which further reduces the service interruption latency during handover.

[0199] Optionally, the method shown in Figure 5 may further include: a second core network element receiving a fourteenth message sent by a target RAN, wherein the fourteenth message is used to instruct the second core network element to send a handover command about the terminal to the source RAN, and the fourteenth message is sent by the target RAN when it determines that the handover of each session is completed.

[0200] For example, when the target RAN determines that the handover of each PDU session is complete based on the handover response information of each PDU session, it sends a handover command (e.g., Namf_Handover_Command) to the AMF. This handover command contains a transparent container from the target RAN to the source RAN and requests the AMF to send a handover command (e.g., Nran_Handover_Command) to the source RAN.

[0201] Optionally, the method shown in Figure 5 may further include: the second core network element sending a handover command (e.g., Nran_Handover_Command) to the source RAN, the handover command containing a transparent container from the target RAN to the source RAN.

[0202] Accordingly, the source RAN sends a handover command (e.g., a Handover command) to the terminal, instructing the terminal to synchronize with the target cell. Further, the terminal synchronizes with the target cell. Optionally, the terminal sends a handover confirmation message (e.g., a Handover Confirm) to the target RAN.

[0203] Optionally, the method shown in Figure 5 may further include: a second core network element receiving a seventeenth message sent by the target RAN, the seventeenth message being used to notify the terminal that the handover from the source RAN to the target RAN has been completed. For example, the target RAN sends a handover notification (e.g., Namf_Handover_Notify) to the AMF, indicating to the AMF that the terminal has completed the handover.

[0204] The communication method proposed in the embodiment shown in Figure 5 can directly interact with the target RAN regarding RAN handover information because the first core network element used for session management can do so without the need for the second core network element to forward the RAN handover information. Therefore, it can solve a series of problems in related technologies, such as low transmission efficiency of handover information, high load on the second core network element, and high coupling between the second and first core network elements, which makes independent upgrades difficult due to the long transmission path of handover information. This achieves the effects of shortening the transmission path of handover information, improving the transmission efficiency of handover information, reducing the load on other core network elements, and decoupling the second and first core network elements.

[0205] As shown in Figure 6, a communication method provided in this application embodiment may include:

[0206] Step 601: During the process of the terminal switching from the source RAN to the target RAN, the source RAN receives a third message sent by the first core network element. The third message is used to instruct the source RAN to forward data to the target RAN through an indirect forwarding tunnel. The indirect forwarding tunnel refers to the data transmission tunnel from the source RAN to the third core network element and then from the third core network element to the target RAN. The first core network element is used for session management.

[0207] The third message carries at least one of the following information:

[0208] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0209] The terminal's session ID;

[0210] The tunnel endpoint identifier (TEID) information of the third core network element is used for user plane management.

[0211] Accordingly, the source RAN can perform data forwarding for the PDU session corresponding to the session ID of the terminal under the first core network element.

[0212] It should be noted that, in this embodiment of the application, since the source RAN does not need to wait for the handover response of all sessions to be completed before it can start data forwarding, and can perform data forwarding in parallel for the data of sessions controlled by different first core network elements, this further reduces the service interruption latency during handover.

[0213] Figure 7 illustrates an interactive schematic diagram of a communication method provided in an embodiment of this application. In Figure 7, the first core network element is SMF, the second core network element is AMF, and the third core network element is UPF, as an example for illustration.

[0214] As shown in Figure 7, a communication method proposed in this application embodiment may include:

[0215] Step 1: Terminal 71 sends a measurement report to source RAN 72. Source RAN 72 makes a handover decision and assigns a first terminal identifier (e.g., S-RAN UE ID) to terminal 71.

[0216] Step 2: The source RAN 72 sends the sixteenth message to the AMF 74 – a handover requirement message (e.g., Namf_Handover_required). The sixteenth message is used to indicate that the terminal needs to hand over from the source RAN to the target RAN 73. The sixteenth message carries the first terminal identifier (e.g., S-RAN UE ID), the ID of the target RAN 73, and the PDU session ID. The S-RAN UE ID is used by the AMF 74 to associate the terminal 71 with the corresponding PDU session ID.

[0217] Step 3: AMF 74 selects SMF 75. In this embodiment, SMF 75 remains unchanged before and after the switch.

[0218] Step 4, AMF 74 sends a second message to SMF 75—a handover notification message (e.g., Nsmf_Handover_Notification). The handover notification message is used to instruct SMF 75 that the terminal needs to hand over from the source RAN to the target RAN 73. The handover notification message includes a first terminal identifier (e.g., S-RAN UE ID), the user permanent identifier SUPI corresponding to the terminal, and the ID of the target RAN 73.

[0219] Step 5, SMF 75 sends a second confirmation message for the second message to AMF 74—a handover notification confirmation message, which contains the user permanent identifier (SUPI) corresponding to the terminal.

[0220] Step 6: SMF 75 selects UPF 76. In this embodiment, UPF 76 remains unchanged before and after the switch.

[0221] Optionally, in step 7, SMF 75 and UPF 76 perform N4 session modification.

[0222] Step 8, AMF 74 sends the eighth message to the target RAN 73 – a handover UE context notification message (e.g., Nran_Handover_UEContext_Notify). This handover UE context notification message contains a first terminal identifier (e.g., S-RAN UE ID), a UE mobility management information list N2 MM, and a PDU session ID. The PDU session ID is used to indicate the PDU session ID information of the UE under this SMF 75.

[0223] Step 9: Target RAN 73 assigns a second terminal identifier (e.g., T-RAN UE ID) to terminal 71 and sends a sixth confirmation message for the eighth message to AMF 74—a handover_UEContext_Notify_ACK message (e.g., Nran_Handover_UEContext_Notify_ACK), which includes the second terminal identifier (e.g., T-RAN UE ID).

[0224] Step 10: SMF 75 sends a first message—a handover request message (e.g., Nran_HandoverRequest)—to the target RAN 73. This handover request message indicates the PDU session ID of the terminal to be handed over and the tunnel endpoint identifier information (e.g., UPF TEID) of UPF 76. Specifically, the handover request message may carry the first terminal identifier (e.g., S-RAN UE ID), PDU session ID, session management information list SM N2, and the tunnel endpoint identifier (TEID) of UPF 76. Since the handover request does not need to be forwarded through AMF 74, the problems of circuitous transmission paths and low transmission efficiency of handover-related information in related technologies can be solved.

[0225] Step 11: The target RAN 73 sends a first confirmation message for the first message to the SMF 75—a handover request confirmation message (e.g., Nran_HandoverRequest_Ack). This handover request confirmation message contains a second terminal identifier (e.g., T-RAN UE ID), the target RAN's tunnel endpoint identifier (e.g., T-RAN TEID), and PDU session ID information indicating whether the handover was successful or failed.

[0226] Optionally, in step 12, SMF 75 and UPF 76 perform N4 session modification.

[0227] Step 13: SMF 75 sends a third message—a handover indication (e.g., Nran_HandoverIndication) message—to source RAN 72, instructing source RAN 72 to begin data forwarding via an indirect forwarding tunnel. This handover indication message includes a first terminal identifier (e.g., S-RAN UE ID), a PDU session ID, and the tunnel endpoint identifier (TEID) information from UPF 76. Since the handover indication does not need to be forwarded via AMF 74, the problems of circuitous transmission paths and low transmission efficiency in related technologies can be solved.

[0228] Optionally, step 13 may also be: the target RAN 73 sends a third message—a handover indication (e.g., Nran_HandoverIndication) message—to the AMF 74, which instructs the AMF 74 to send a handover indication (e.g., Nran_HandoverIndication) message to the source RAN 72, triggering the source RAN 72 to start data forwarding through the indirect forwarding tunnel.

[0229] Step 14: The source RAN 72 can perform data forwarding for the PDU session corresponding to the PDU session ID of terminal 71 under SMF 75. It should be noted that the source RAN 72 does not need to wait for the handover response of all PDU sessions to be completed before it can start data forwarding, and it can perform data forwarding in parallel for PDU sessions controlled by different SMF 75s, which can further reduce service interruption latency during handover.

[0230] Step 15: The target RAN 73 monitors the handover response of each PDU session.

[0231] Step 16: After the handover of each PDU session is completed, the target RAN 73 sends the fourteenth message to the AMF 74—a handover command (e.g., Namf Handover_Command). This handover command contains a transparent container from the target RAN to the source RAN. This handover command is used to request the AMF 74 to send a handover command to the source RAN 72.

[0232] Step 17: AMF 74 sends a handover command (e.g., Nran_Handover_Command) to source RAN 72, which contains a transparent container from the target RAN to the source RAN.

[0233] Step 18: Source RAN 72 sends a handover command (e.g., a handover command) to terminal 71, which instructs terminal 71 to synchronize with the target cell.

[0234] Step 19: Terminal 71 synchronizes with the target cell.

[0235] Step 20: Terminal 71 sends a handover confirmation (e.g., Handover Confirm) message to target RAN 73.

[0236] Step 21: Target RAN 73 sends the seventeenth message to AMF 74 – a handover notification (e.g., Namf_Handover_Notify), which is used to indicate to AMF 74 that the terminal handover has been completed.

[0237] Step 22: Target RAN 73 sends a seventh message to SMF 75 – a handover notification (e.g., Namf_Handover_Notify), which is used to indicate to SMF 75 that the terminal handover has been completed.

[0238] In the embodiment shown in Figure 7, the SMF directly sends a handover request to the target RAN and receives a handover response message from the target RAN. The target RAN monitors the PDU session handover responses. Upon receiving a handover response corresponding to a PDU session controlled by an SMF, the SMF or the target RAN triggers the source RAN to forward data. When the handover responses corresponding to all PDU sessions requiring modification controlled by multiple SMFs have been completed (regardless of success or failure), the target RAN triggers the AMF to send a handover command to the source RAN. Because the source RAN and target RAN can communicate directly with the SMF during the handover process, the problems of low transmission efficiency, high AMF load, and large service interruption latency during handover caused by forwarding through the AMF are solved, achieving gains in improved transmission efficiency and reduced service interruption latency during handover. Furthermore, since the source RAN does not need to wait for all session handover responses to complete before starting data forwarding, and can forward data in parallel for sessions controlled by different SMFs, this further reduces service interruption latency during handover.

[0239] The embodiment shown in Figure 7 provides a communication method that is applicable to both intra-system handover in 5G / 6G and inter-system handover. For example, when a UE switches from 5G to 6G, the target system is 6G. In the 6G system, the SMF sends a handover request to the target RAN.

[0240] As shown in Figure 8, an embodiment of this application provides a communication method that may include:

[0241] Step 801: During the process of the terminal switching from the source RAN to the target RAN, the first core network element receives a fifth message sent by the target RAN, wherein the fifth message is used to request the terminal to be switched to the target RAN, and the first core network element is used for session management.

[0242] The fifth message carries at least one of the following information:

[0243] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0244] The second terminal identifier is an identifier assigned to the terminal by the target RAN;

[0245] The terminal's session ID;

[0246] The Tunnel Endpoint Identifier (TEID) information of the target RAN is used by the first core network element and the third core network element to modify the session of the terminal.

[0247] For example, the SMF can receive a fifth message sent by the target RAN—a handover request message (e.g., Nran_HandoverRequest). This handover request message indicates the PDU session ID of the terminal to be handed over. The message may include a first terminal identifier (e.g., S-RAN UE ID), the tunnel endpoint identifier of the target RAN (e.g., T-RAN TEID), the PDU session ID, and a session management information list SM N2. Since the handover request message does not need to be forwarded through the AMF, the problems of circuitous transmission paths and low transmission efficiency of handover-related messages in related technologies can be solved.

[0248] Optionally, the method shown in Figure 8 may further include: the first core network element selecting a third core network element, wherein the third core network element is used for user plane management, for example, the third core network element may be a UPF. In this embodiment, the third core network element may remain unchanged before and after the handover.

[0249] Optionally, the method shown in Figure 8 may further include: the first core network element and the third core network element performing session modification. For example, the SMF may perform N4 session modification with the UPF.

[0250] Optionally, the method shown in Figure 8 may further include: the first core network element sending a third confirmation message to the target RAN in response to the fifth message.

[0251] The third confirmation message carries at least one of the following information:

[0252] The second terminal identifier is an identifier assigned to the terminal by the target RAN;

[0253] The terminal's session ID;

[0254] The target RAN's tunnel endpoint identifier, T-RAN TEID;

[0255] The Tunnel Endpoint Identifier (TEID) information of the third core network element.

[0256] For example, the SMF sends a third acknowledgment message for the fifth message to the target RAN—a handover request acknowledgment message (e.g., Nran_HandoverRequest_Ack), which contains the T-RAN TEID, T-RAN TEID, UPF TEID, and PDU session ID information.

[0257] Optionally, before step 801, the method shown in FIG8 may further include: the first core network element receiving a sixth message sent by the second core network element, wherein the sixth message is used to instruct the first core network element that the terminal needs to switch from the source RAN to the target RAN.

[0258] The sixth message carries at least one of the following information:

[0259] The first terminal identifier (e.g., S-RAN UE ID) is an identifier assigned to the terminal by the source RAN;

[0260] The second terminal identifier (e.g., T-RAN UE ID) is an identifier assigned to the terminal by the target RAN;

[0261] The user permanent identifier SUPI corresponding to the terminal;

[0262] The ID of the target RAN.

[0263] For example, the AMF sends a sixth message to the SMF—a handover notification message (e.g., Nsmf_Handover_Notification). This handover notification message is used to instruct the SMF terminal that it needs to hand over from the source RAN to the target RAN. The handover notification message contains the S-RAN UE ID, T-RAN UE ID, the user permanent identifier SUPI corresponding to the UE, and the ID of the target RAN.

[0264] Optionally, before step 801, the method shown in FIG8 may further include: the first core network element sending a fourth confirmation message for the sixth message to the second core network element, wherein the fourth confirmation message carries the user permanent identifier SUPI corresponding to the terminal.

[0265] For example, the SMF can send a fourth confirmation message for the sixth message to the AMF—a handover notification confirmation message (e.g., Nsmf_Handover_Notification_Ack), which contains the user permanent identifier (SUPI) corresponding to the UE.

[0266] Optionally, the method shown in Figure 8 may further include: the first core network element receiving a seventh message sent by the target RAN, the seventh message being used to notify the terminal to complete the handover from the source RAN to the target RAN.

[0267] For example, the SMF can receive a seventh message sent by the target RAN—a handover notification (e.g., Nsmf_Handover_Notify), which is used to indicate to the SMF that the terminal has completed the handover.

[0268] The communication method proposed in the embodiment shown in Figure 8 can directly interact with the target RAN regarding RAN handover information because the first core network element used for session management can do so without the need for the second core network element to forward the RAN handover information. Therefore, it can solve a series of problems in related technologies, such as low transmission efficiency of handover information, high load on the second core network element, and high coupling between the second and first core network elements, which makes independent upgrades difficult due to the long transmission path of handover information. This achieves the effects of shortening the transmission path of handover information, improving the transmission efficiency of handover information, reducing the load on other core network elements, and decoupling the second and first core network elements.

[0269] As shown in Figure 9, an embodiment of this application provides a communication method that may include:

[0270] Step 901: During the process of the terminal switching from the source RAN to the target RAN, the target RAN sends a fifth message to the first core network element. The fifth message is used to request the terminal to be switched to the target RAN. The first core network element is used for session management.

[0271] The fifth message carries at least one of the following information:

[0272] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0273] The second terminal identifier is an identifier assigned to the terminal by the target RAN;

[0274] The terminal's session ID;

[0275] The Tunnel Endpoint Identifier (TEID) information of the target RAN is used by the first core network element and the third core network element to modify the session of the terminal.

[0276] For example, the target RAN can send a fifth message—a handover request message (e.g., Nran_HandoverRequest)—to the SMF. This handover request message indicates the PDU session ID of the terminal to be handed over. The message may include a first terminal identifier (e.g., S-RAN UE ID), the tunnel endpoint identifier of the target RAN (e.g., T-RAN TEID), the PDU session ID, and a session management information list SM N2. Since the handover request message does not need to be forwarded through the AMF, the problems of circuitous transmission paths and low transmission efficiency of handover-related messages in related technologies can be solved.

[0277] Optionally, the method shown in FIG9 may further include: the target RAN receiving a third confirmation message for the fifth message sent by the first core network element.

[0278] The third confirmation message carries at least one of the following information:

[0279] The second terminal identifier is an identifier assigned to the terminal by the target RAN;

[0280] The terminal's session ID;

[0281] The target RAN's tunnel endpoint identifier, T-RAN TEID;

[0282] The Tunnel Endpoint Identifier (TEID) information of the third core network element.

[0283] Optionally, before step 901, the method shown in FIG9 may further include: the target RAN receiving the eleventh message sent by the second core network element.

[0284] The eleventh message carries at least one of the following information:

[0285] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0286] The ID of the first core network element;

[0287] UE context information related to mobility management;

[0288] The session ID of the terminal is the session information of the terminal under the first core network element.

[0289] For example, the AMF can send an eleventh message to the target RAN—a handover UE context notification message (e.g., Nran_Handover_UEContext_Notify). This handover UE context notification message contains the S-RAN UE ID, GU SMF ID, UE mobility management information list N2 MM, and PDU session ID. The handover UE context notification message is used to indicate the PDU session ID of the terminal under this SMF.

[0290] Optionally, before step 901, the method shown in FIG9 may further include: the target RAN sending a seventh confirmation message for the eleventh message to the second core network element, wherein the seventh confirmation message carries a second terminal identifier (e.g., T-RAN UE ID), and the second terminal identifier is an identifier assigned by the target RAN to the terminal.

[0291] For example, the target RAN assigns a T-RAN UE ID to the terminal and sends a seventh confirmation message for the eleventh message to the AMF—a handover_UE context notification confirmation message (e.g., Nran_Handover_UEContext_Notify_ACK), which includes the T-RAN UE ID.

[0292] Optionally, the method shown in Figure 9 may further include: the target RAN sending a twelfth message to the second core network element, wherein the twelfth message is used by the second core network element to instruct the source RAN to forward data to the target RAN through an indirect forwarding tunnel, wherein the indirect forwarding tunnel refers to the data transmission tunnel from the source RAN to the third core network element, and then from the third core network element to the target RAN.

[0293] The twelfth message carries at least one of the following information:

[0294] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0295] The terminal's session ID;

[0296] The Tunnel Endpoint Identifier (TEID) information of the third core network element.

[0297] For example, the target RAN can send a twelfth message—a handover indication (e.g., Nran_HandoverIndication)—to the AMF. This handover indication message contains the S-RAN UE ID, PDU session ID, and UPF TEID. Correspondingly, the AMF can send a handover indication (e.g., Nran_HandoverIndication) message to the source RAN. This handover indication message may contain the S-RAN UE ID, PDU session ID, and UPF TEID information. This handover indication message can be used to indicate to the source RAN that it can begin data forwarding through the indirect forwarding tunnel.

[0298] Optionally, a handover indication message can be sent from the first core network element (such as SMF) to the source RAN. This handover indication message may include the first terminal identifier, the terminal's session ID, and the tunnel endpoint identifier (TEID) information of the third core network element. This handover indication message can be used to instruct the source RAN to start data forwarding through the indirect forwarding tunnel. It is understood that since forwarding through the second core network element (such as AMF) is not required, the problems of detours and low transmission efficiency of handover-related information transmission paths in related technologies can be solved.

[0299] Accordingly, the source RAN performs data forwarding for the PDU session corresponding to the session ID of the terminal under the first core network element. In this embodiment, the source RAN does not need to wait for the handover response of all sessions to be completed before it can start data forwarding, and can perform data forwarding in parallel for the data of sessions controlled by different first core network elements, thereby further reducing the service interruption latency during handover.

[0300] Optionally, the method shown in Figure 9 may further include:

[0301] The target RAN monitors the handover response information of each session of the terminal;

[0302] When the target RAN determines that the handover of each session is completed based on the handover response information of each session, it sends a thirteenth message about the terminal to the second core network element, wherein the thirteenth message is used to instruct the second core network element to send a handover command about the terminal to the source RAN.

[0303] For example, the target RAN monitors the handover response status of each PDU session ID. Further, after determining that the handover of each PDU session is complete based on the handover response information of each PDU session, the target RAN sends a handover command (e.g., Namf_Handover_Command) to the AMF. This handover command contains a transparent container from the target RAN to the source RAN, requesting the AMF to send a handover command (e.g., Nran_Handover_Command) to the source RAN.

[0304] Accordingly, the source RAN can further send a handover command (e.g., a Handover command) to the terminal, which instructs the terminal to synchronize with the target cell; the terminal synchronizes with the target cell after receiving the handover command; optionally, the terminal can also send a handover confirmation (e.g., a Handover Confirm) message to the target RAN.

[0305] Optionally, the method shown in Figure 9 may further include: the target RAN sending a seventeenth message to the second core network element, the seventeenth message being used to notify the terminal that the handover from the source RAN to the target RAN has been completed. For example, the target RAN sends a handover notification (e.g., Namf_Handover_Notify) to the AMF as the seventeenth message, the handover notification being used to indicate to the AMF that the terminal has completed the handover.

[0306] Optionally, the method shown in Figure 9 may further include: the target RAN sending an eighteenth message to the first core network element after the handover is completed, wherein the eighteenth message is used to notify the terminal that the handover from the source RAN to the target RAN has been completed. For example, the target RAN sends a handover notification (e.g., Namf_Handover_Notify) to the SMF as the eighteenth message, which is used to indicate to the AMF that the terminal has completed the handover.

[0307] The communication method proposed in the embodiment shown in Figure 9 can directly interact with the first core network element used for session management to exchange RAN handover related information, without the need for the second core network element to forward the RAN handover related information. Therefore, it can solve a series of problems in related technologies, such as low transmission efficiency of handover related information, high load on the second core network element, and high coupling between the second core network element and the first core network element, which makes it difficult to upgrade independently due to the long transmission path of handover related information. Thus, it achieves the effects of shortening the transmission path of handover related information, improving the transmission efficiency of handover related information, reducing the load on other core network elements, and decoupling the second core network element from the first core network element.

[0308] As shown in Figure 10, a communication method provided in this application embodiment may include:

[0309] Step 1001: During the process of the terminal switching from the source RAN to the target RAN, the second core network element sends an eleventh message to the target RAN. The eleventh message is used to trigger the target RAN to send a fifth message to the first core network element. The fifth message is used to request the terminal to switch to the target RAN. The first core network element is used for session management.

[0310] The eleventh message carries at least one of the following information:

[0311] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0312] The ID of the first core network element, such as the GU SMF ID;

[0313] UE context information related to mobility management;

[0314] The session ID of the terminal is the session information of the terminal under the first core network element.

[0315] Optionally, the method shown in FIG10 may further include: the second core network element receiving a seventh confirmation message for the eleventh message sent by the target RAN, wherein the seventh confirmation message carries a second terminal identifier, the second terminal identifier being an identifier assigned to the terminal by the target RAN.

[0316] Optionally, before step 1001, the terminal sends a measurement report to the source RAN, the source RAN makes a handover decision, and the source RAN assigns a first terminal identifier (e.g., S-RAN UE ID) to the terminal. Accordingly, the method shown in Figure 10 may further include: the second core network element receiving the eighteenth message sent by the source RAN, wherein the eighteenth message is used to indicate that the terminal needs to hand over from the source RAN to the target RAN.

[0317] The eighteenth message carries at least one of the following information:

[0318] In this embodiment, the first terminal identifier (e.g., S-RAN UE ID) is used to associate the terminal with the second core network element and the corresponding session ID.

[0319] The ID of the first core network element, such as the GU SMF ID;

[0320] Target RAN ID;

[0321] The terminal's session ID.

[0322] For example, the source RAN sends a handover request message (e.g., Namf_Handover_required) to the AMF as the eighteenth message. This handover message contains the S-RAN UE ID, GU SMF ID, target RAN ID, and PDU session ID. The S-RAN UE ID is used by the AMF to associate the UE with its PDU session ID.

[0323] Optionally, before step 1001, the method shown in Figure 10 may further include: the second core network element selects the first core network element according to the eighteenth message. For example, the AMF selects the SMF according to the GU SMF ID in the eighteenth message. In this embodiment, the SMF may remain unchanged before and after the handover.

[0324] Optionally, the method shown in FIG10 may further include: the second core network element sending a sixth message to the first core network element, wherein the sixth message is used to instruct the first core network element that the terminal needs to switch from the source RAN to the target RAN.

[0325] The sixth message carries at least one of the following information:

[0326] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0327] The second terminal identifier is an identifier assigned to the terminal by the target RAN;

[0328] The user permanent identifier SUPI corresponding to the terminal;

[0329] The ID of the target RAN.

[0330] Optionally, the method shown in FIG10 may further include: the second core network element receiving a fourth confirmation message sent by the first core network element for the sixth message, wherein the fourth confirmation message carries the user permanent identifier SUPI corresponding to the terminal.

[0331] Optionally, the method shown in FIG10 may further include: the second core network element receiving a twelfth message sent by the target RAN, wherein the twelfth message is used by the second core network element to instruct the source RAN to forward data to the target RAN through an indirect forwarding tunnel, wherein the indirect forwarding tunnel refers to the data transmission tunnel from the source RAN to the third core network element, and then from the third core network element to the target RAN.

[0332] The twelfth message carries at least one of the following information:

[0333] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0334] The terminal's session ID;

[0335] The Tunnel Endpoint Identifier (TEID) information of the third core network element.

[0336] Optionally, the method shown in FIG10 may further include: the second core network element receiving a thirteenth message about the terminal sent by the target RAN, wherein the thirteenth message instructs the second core network element to send a handover command about the terminal to the source RAN.

[0337] Optionally, the method shown in Figure 10 may further include: the second core network element sending a handover command about the terminal to the source RAN.

[0338] Accordingly, the source RAN can further send a handover command (e.g., a Handover command) to the terminal, which instructs the terminal to synchronize with the target cell; the terminal synchronizes with the target cell after receiving the handover command; optionally, the terminal can also send a handover confirmation (e.g., a Handover Confirm) message to the target RAN.

[0339] Optionally, the method shown in Figure 10 may further include: the second core network element receiving a seventeenth message sent by the target RAN, the seventeenth message being used to notify the terminal that the handover from the source RAN to the target RAN has been completed. For example, the target RAN sends a handover notification (e.g., Namf_Handover_Notify) to the AMF as the seventeenth message, which is used to indicate to the AMF that the terminal has completed the handover.

[0340] The communication method proposed in the embodiment shown in Figure 10 can directly interact with the target RAN regarding RAN handover information because the first core network element used for session management can do so without the need for the second core network element to forward some RAN handover-related information. Therefore, it can solve a series of problems in related technologies, such as low transmission efficiency of handover-related information, high load on the second core network element, and high coupling between the second and first core network elements, which make independent upgrades difficult due to the long transmission path of handover-related information. This achieves the effects of shortening the transmission path of handover-related information, improving the transmission efficiency of handover-related information, reducing the load on other core network elements, and decoupling the second and first core network elements.

[0341] Figure 11 shows an interactive schematic diagram of a communication method provided in an embodiment of this application. In Figure 11, the first core network element is SMF, the second core network element is AMF, and the third core network element is UPF, as an example for illustration.

[0342] As shown in Figure 11, a communication method proposed in this application embodiment may include:

[0343] Step 1: Terminal 111 sends a measurement report to source RAN 112. Source RAN 112 makes a handover decision and assigns a first terminal identifier (S-RAN UE ID) to terminal 111.

[0344] Step 2: Source RAN 112 sends the eighteenth message to AMF 114 – a handover request message (e.g., Namf_Handover_required). This handover message contains the S-RAN UE ID, GU SMF ID, the ID of the target RAN 113, and the PDU session ID. The S-RAN UE ID is used by AMF 114 to associate terminal 111 and its PDU session ID.

[0345] Step 3: AMF 114 selects SMF 115 according to the eighteenth message. In this embodiment, SMF 115 can remain unchanged before and after the switch.

[0346] Step 4, AMF 114 sends the eleventh message to the target RAN 113—a handover UE context notification message (e.g., Nran_Handover_UEContext_Notify). This handover UE context notification message may contain the S-RAN UE ID, GU SMF ID, UE mobility management information list N2 MM, and PDU session ID. The PDU session ID is used to indicate the PDU session ID of the terminal 111 that needs to be handed over under the SMF 115.

[0347] Step 5: Target RAN 113 assigns a second terminal identifier (e.g., T-RAN UE ID) to the UE and sends a seventh confirmation message for the eleventh message to AMF 114—a handover_UE context notification confirmation message (e.g., Nran_Handover_UEContext_Notify_ACK). The handover_UE context notification confirmation message includes the T-RAN UE ID.

[0348] Step 5a, AMF 114 sends a sixth message to SMF 115—a handover notification message (e.g., Nsmf_Handover_Notification). This handover notification message is used to indicate that SMF 115 terminal 111 needs to hand over from source RAN 112 to target RAN 113. The handover notification message contains the S-RAN UE ID, the user permanent identifier SUPI corresponding to the UE, and the ID of the target RAN 113.

[0349] Step 5b, SMF 115 sends a fourth confirmation message for the sixth message to AMF 114—a handover notification confirmation message (e.g., Nsmf_Handover_Notification_Ack), which contains the user permanent identifier (SUPI) corresponding to the UE.

[0350] Step 6: Target RAN 113 sends a fifth message—a handover request message (e.g., Nran_HandoverRequest)—to SMF 115. This handover request message requests a handover of terminal 111 to target RAN 113. The message includes the S-RAN UE ID, T-RAN UE ID, PDU session ID, target RAN 113's TEID, and session management information list SMN2. Since forwarding through AMF 114 is not required, the problems of circuitous transmission paths and low transmission efficiency of handover-related messages in related technologies can be solved.

[0351] Step 7: SMF 115 selects UPF 116. In this embodiment, UPF 116 can remain unchanged before and after the switch.

[0352] Optionally, in step 8, SMF 115 and UPF 116 perform N4 session modification.

[0353] Step 9: SMF 115 sends a third confirmation message for the fifth message to target RAN 113—a handover request confirmation message (e.g., Nran_HandoverRequest_Ack). This handover request confirmation message may contain the TEID of target RAN 113, the TEID of UPF 116, and PDU session ID information.

[0354] Step 10: Target RAN 113 sends the twelfth message to AMF 114 – a handover indication (e.g., Nran_HandoverIndication) message, which may contain the S-RAN UE ID, PDU session ID, and UPF 116's TEID.

[0355] Step 11: AMF 114 sends a handover indication (e.g., Nran_HandoverIndication) message to source RAN 112. The handover indication message may contain S-RAN UE ID, PDU session ID, and UPF 116 TEID. The handover indication message is used to indicate that source RAN 112 can start data forwarding through the indirect forwarding tunnel.

[0356] Alternatively, as an alternative to steps 10 and 11, the target RAN 113 may also send a handover indication (e.g., Nran_HandoverIndication) message to the SMF 115, which in turn sends a handover indication (e.g., Nran_HandoverIndication) message to the source RAN 112, indicating that the source RAN 112 can forward data through the indirect forwarding tunnel. Since forwarding through the AMF 114 is not required, the problems of circuitous transmission paths and low transmission efficiency related to handover information in related technologies can be solved.

[0357] Step 12: The source RAN 112 can perform data forwarding for the UE under the PDU session ID of the SMF 115. It should be noted that in this embodiment, the source RAN 112 does not need to wait for the handover response of all PDU sessions to be completed before it can start data forwarding, and can perform data forwarding in parallel for PDU sessions controlled by different SMFs 115, thus further reducing the service interruption latency during handover.

[0358] Step 13: The target RAN 113 monitors the handover response of each PDU session.

[0359] Step 14: After determining that the handover of each PDU session is complete, the target RAN 113 sends a thirteenth message to the AMF 114—a handover command (e.g., Namf_Handover_Command). This handover command contains a transparent container from the target RAN to the source RAN. This handover command is used to request the AMF 114 to send a handover command to the source RAN 112.

[0360] Step 15, AMF 114 sends a handover command (e.g., Nran_Handover_Command) to source RAN 112, which contains a transparent container from the target RAN to the source RAN.

[0361] Step 16: Source RAN 112 sends a handover command (e.g., a handover command) to terminal 111, which instructs terminal 111 to synchronize with the target cell.

[0362] Step 17: Terminal 111 synchronizes with the target cell.

[0363] Step 18: Terminal 111 sends a handover confirmation (e.g., Handover Confirm) message to target RAN 113.

[0364] Step 19: Target RAN 113 sends the seventeenth message—a handover notification (e.g., Namf_Handover_Notify)—to AMF 114. This handover notification is used to indicate to AMF 114 that the terminal handover has been completed.

[0365] Step 20: Target RAN 113 sends the eighteenth message—a handover notification (e.g., Nsmf_Handover_Notify)—to SMF 115. This handover notification is used to indicate to SMF 115 that the terminal handover has been completed.

[0366] In the embodiment shown in Figure 11, the target RAN directly sends a handover request to the SMF and receives a handover response message from the SMF. The target RAN monitors the PDU session handover responses. Upon receiving a handover response from a PDU session controlled by a certain SMF, the SMF or the target RAN triggers the source RAN to forward data. When the handover responses for all PDU sessions controlled by multiple SMFs that need to be handed over have been completed (regardless of success or failure), the target RAN triggers the AMF or SMF to send a handover command to the source RAN. Because the source RAN and target RAN can communicate directly with the SMF during the handover process, the problems of low transmission efficiency, high AMF load, and large service interruption latency during handover caused by forwarding through the AMF are solved, achieving gains in improving transmission efficiency and reducing service interruption latency during handover. Furthermore, since the source RAN does not need to wait for the handover responses of all sessions to be completed before starting data forwarding, and can forward data in parallel for sessions controlled by different SMFs, this further reduces service interruption latency during handover.

[0367] The embodiment shown in Figure 11 provides a communication method that is applicable to both intra-system handover in 5G / 6G and inter-system handover. For example, when a UE switches from 5G to 6G, the target system is 6G. In the 6G system, the target RAN sends a handover request to the SMF.

[0368] As shown in Figure 12, a communication method provided in this application embodiment may include:

[0369] Step 1201: When the terminal switches from the source RAN to the target RAN, the first core network element receives the tenth message sent by the target RAN, wherein the tenth message is used to instruct the first core network element to control the third core network element to switch the user plane path of the terminal's session from the source RAN to the target RAN, and the first core network element is used for session management.

[0370] In some embodiments, the tenth message is sent by the target RAN and the source RAN after modifying the session based on the Xn interface, where the Xn interface is an interface used for communication between the source RAN and the target RAN.

[0371] The tenth message carries at least one of the following information:

[0372] The first terminal identifier (e.g., S-RAN UE ID) is an identifier assigned to the terminal by the source RAN;

[0373] The second terminal identifier (e.g., T-RAN UE ID) is an identifier assigned to the terminal by the target RAN.

[0374] For example, the target RAN can send a tenth message to the SMF—a path switch request message (e.g., Nsmf_PathSwitchRequest), which may contain the S-RAN UE ID and the T-RAN UE ID.

[0375] Optionally, the first core network element can perform user plane path switching with the third core network element regarding the terminal. For example, the SMF can perform user plane path switching with the UPF regarding the terminal.

[0376] Optionally, the method shown in Figure 12 may further include: the first core network element sending a fifth confirmation message for the tenth message to the target RAN. For example, the SMF may send a fifth confirmation message for the tenth message—a path switch request confirmation (e.g., Nsmf_PathSwitchRequestAck) message—to the target RAN.

[0377] The embodiment shown in Figure 12 provides a communication method that, since it does not require forwarding path switching requests from a second core network element (such as AMF) to a first core network element (such as SMF), can solve the problem of low transmission efficiency caused by the detour of the transmission path for switching related information in the related technology.

[0378] As shown in Figure 13, a communication method provided in this application embodiment may include:

[0379] Step 1301: When the terminal switches from the source RAN to the target RAN, the target RAN sends a tenth message to the first core network element, wherein the tenth message is used to instruct the first core network element to control the third core network element to switch the user plane path of the terminal's session from the source RAN to the target RAN, and the first core network element is used for session management.

[0380] In some embodiments, the tenth message is sent by the target RAN and the source RAN after modifying the session based on the Xn interface, where the Xn interface is an interface used for communication between the source RAN and the target RAN.

[0381] The tenth message carries at least one of the following information:

[0382] The first terminal identifier (e.g., S-RAN UE ID) is an identifier assigned to the terminal by the source RAN;

[0383] The second terminal identifier (e.g., T-RAN UE ID) is an identifier assigned to the terminal by the target RAN.

[0384] For example, the target RAN can send a tenth message to the SMF—a path switch request message (e.g., Nsmf_PathSwitchRequest), which may contain the S-RAN UE ID and the T-RAN UE ID.

[0385] Optionally, the method shown in Figure 13 may further include: the target RAN receiving a fifth acknowledgment message for the tenth message sent by the first core network element. For example, the SMF may send a fifth acknowledgment message for the tenth message—a path switch request acknowledgment (e.g., Nsmf_PathSwitchRequestAck) message—to the target RAN.

[0386] Optionally, the method shown in Figure 13 may further include: the target RAN sending a ninth message to a second core network element, wherein the ninth message is used to request that the user plane path of the terminal's session be switched from the source RAN to the target RAN.

[0387] In some embodiments, the ninth message is sent by the target RAN and the source RAN after modifying the session based on the Xn interface, where the Xn interface is an interface used for communication between the source RAN and the target RAN.

[0388] The ninth message carries at least one of the following information:

[0389] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0390] The second terminal identifier is an identifier assigned to the terminal by the target RAN.

[0391] For example, the target RAN can send a ninth message to the AMF—a path switch request message (e.g., Nsmf_PathSwitchRequest), which may contain the S-RAN UE ID and the T-RAN UE ID.

[0392] Optionally, the method shown in Figure 13 may further include: the target RAN receiving a ninth acknowledgment message for the ninth message sent by the second core network element. For example, the AMF may send a ninth acknowledgment message for the ninth message—a path switch request acknowledgment (e.g., Nsmf_PathSwitchRequestAck) message—to the target RAN.

[0393] Accordingly, the target RAN can send a UE context release message (e.g., UEContext Release) to the source RAN.

[0394] The embodiment shown in Figure 13 provides a communication method that, since it does not require forwarding path switching requests from a second core network element (such as AMF) to a first core network element (such as SMF), can solve the problem of low transmission efficiency caused by the detour of the transmission path for switching related information in the related technology.

[0395] As shown in Figure 14, a communication method provided in this application embodiment may include:

[0396] Step 1401: When the terminal switches from the source RAN to the target RAN, the second core network element receives a ninth message sent by the target RAN, wherein the ninth message is used to request that the user plane path of the terminal's session be switched from the source RAN to the target RAN.

[0397] In some embodiments, the ninth message is sent by the target RAN and the source RAN after modifying the session based on the Xn interface, where the Xn interface is an interface used for communication between the source RAN and the target RAN.

[0398] The ninth message carries at least one of the following information:

[0399] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0400] The second terminal identifier is an identifier assigned to the terminal by the target RAN.

[0401] Optionally, the method shown in Figure 14 may further include: the second core network element sending a ninth confirmation message to the target RAN in response to the ninth message.

[0402] The embodiment shown in Figure 14 provides a communication method that, since it does not require forwarding path switching requests from a second core network element (such as AMF) to a first core network element (such as SMF), can solve the problem of low transmission efficiency caused by the detour of the transmission path for switching related information in the related technology.

[0403] Figure 15 shows a flowchart illustrating a communication method provided in an embodiment of this application. In Figure 15, an example is provided where the first core network element is SMF, the second core network element is AMF, and the third core network element is UPF.

[0404] As shown in Figure 15, a communication method proposed in this application embodiment may include:

[0405] Step 1: Terminal 151 sends a measurement report to source RAN 152.

[0406] Step 2, the source RAN 152 makes a handover decision (e.g., Handover Decision) and assigns a first terminal identifier (e.g., S-RAN UE ID) to the terminal 151.

[0407] Step 3: Source RAN 152 sends the nineteenth message—a handover request message—to target RAN 153. This handover request message contains the S-RAN UE ID and an RRC transparent container. The RRC transparent container contains the identifier of target RAN 153 (e.g., target ID), the relationship information between the ID of GU SMF 155 and PDU session ID. This information is used in step 9 for target RAN 153 to identify SMF 155 and send a path switch request to SMF 155.

[0408] Step 4: Target RAN 153 performs admission control and assigns a second terminal identifier (e.g., T-RAN UE ID) to the UE.

[0409] Step 5: Target RAN 153 sends the tenth acknowledgment message for the nineteenth message to source RAN 152—a handover request ACK message. This handover request ACK message contains an RRC transparent container, which contains the ID of GU SMF 155 and PDU session ID information.

[0410] Step 6: Source RAN 152 prepares to initiate a handover. Optionally, source RAN 152 distributes cached data and new data from UPF 156. Optionally, terminal 151 detaches from the source cell and synchronizes to the target cell.

[0411] Step 7: Source RAN 152 performs Serial Number Status Transfer (SN Status Transfer) to target RAN 153.

[0412] Step 8: The handover of terminal 151, source RAN 152, and target RAN 153 is completed (e.g., RAN Handover completion).

[0413] Step 8a: Target RAN 153 notifies source RAN 152 of successful handover (e.g., Handover Success).

[0414] Step 8b: Source RAN 152 performs a sequence number status transfer (SN Status Transfer) to target RAN 153.

[0415] Step 9: Target RAN 153 sends a ninth message to AMF 154—a path switch request message (e.g., Namf_PathSwitchRequest), which contains the S-RAN UE ID and T-RAN UE ID.

[0416] Step 10: AMF 154 sends a ninth acknowledgment message for the ninth message—a path switch request acknowledgment message (e.g., Nsmf_PathSwitchRequestAck)—to the target RAN 153.

[0417] Step 11: Target RAN 153 sends the tenth message—Path Switching Request message (e.g., Nsmf_PathSwitchRequest)—to SMF 155. This Path Switching Request message contains the S-RAN UE ID and T-RAN UE ID.

[0418] Step 12, UPF 156 performs a path switch.

[0419] Step 13, SMF 155 sends the fifth acknowledgment message for the tenth message to the target RAN 153—path switch request acknowledgment (e.g., Nsmf_PathSwitchRequestAck).

[0420] Step 14: Target RAN 153 sends a UE context release message (e.g., UEContext Release) to source RAN 152.

[0421] In the embodiment shown in Figure 15, the source RAN and the target RAN complete the intra-system handover based on the Xn interface. The N2 interface is serviced, but the Xn interface is not serviced. After the handover is completed, the target RAN directly requests path handover from the AMF or SMF.

[0422] The embodiment shown in Figure 15 provides a communication method that, since it does not require forwarding path switching requests from a second core network element (such as AMF) to a first core network element (such as SMF), can solve the problem of low transmission efficiency caused by the detour of the transmission path for switching related information in related technologies.

[0423] The communication method provided in the embodiments of this application has been described above. The communication method provided in the embodiments of this application can be executed by a communication device. This application uses the example of a communication device executing the communication method to illustrate the communication device provided in the embodiments of this application.

[0424] As shown in Figure 16, an embodiment of this application provides a communication device 1600, which can be applied to a first core network element. The first core network element is used for session management. The communication device 1600 may include: a sending module 1601, which is used to send a first message to the target RAN during the process of a terminal switching from a source RAN to a target RAN. The first message is used to request the terminal to switch to the target RAN.

[0425] In some embodiments, the first core network element may be an SMF.

[0426] In some embodiments, the first message may carry at least one of the following information:

[0427] The first terminal identifier (e.g., S-RAN UE ID) is an identifier assigned to the terminal by the source RAN;

[0428] The terminal's session ID, as an example, can be a PDU session, and the terminal's session ID can be a PDU session ID;

[0429] The Tunnel Endpoint Identifier (TEID) information of the third core network element is used for user plane management. For example, the third core network element can be a UPF.

[0430] Optionally, the communication device 1600 shown in FIG16 may further include: a receiving module for receiving a first acknowledgment message sent by the target RAN in response to the first message.

[0431] The first confirmation message may carry at least one of the following information:

[0432] The second terminal identifier (e.g., T-RAN UE ID) is the identifier assigned to the terminal by the target RAN;

[0433] The Tunnel Endpoint Identifier (TEID) information of the target RAN is used by the first core network element and the third core network element to modify the session of the terminal.

[0434] Optionally, if the terminal's session is a PDU session, the first core network element and the third core network element modify the TEID information of the target RAN regarding the terminal's N4 session.

[0435] Optionally, in the communication device 1600 shown in FIG16, the receiving module may also be used to: receive a second message sent by a second core network element, wherein the second message is used to instruct the first core network element that the terminal needs to switch from the source RAN to the target RAN.

[0436] The second message carries at least one of the following information:

[0437] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0438] The terminal corresponds to the user's permanent identifier (SUPI).

[0439] The ID of the target RAN.

[0440] Optionally, in the communication device 1600 shown in FIG16, the sending module 1601 may also be used to: send a second confirmation message for the second message to the second core network element, wherein the second confirmation message carries the user permanent identifier SUPI corresponding to the terminal.

[0441] Optionally, the communication device 1600 shown in FIG16 may further include: a processing module, used to select a third core network element according to the second message, for example, the SMF selects the UPF. Optionally, in this embodiment, the UPF remains unchanged before and after the switch.

[0442] Optionally, in the communication device 1600 shown in FIG16, the sending module 1601 may also be used to: send a third message to the source RAN, wherein the third message is used to instruct the source RAN to forward data to the target RAN through an indirect forwarding tunnel, wherein the indirect forwarding tunnel refers to the data transmission tunnel from the source RAN to the third core network element and then from the third core network element to the target RAN.

[0443] The third message may carry at least one of the following information:

[0444] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0445] The terminal's session ID;

[0446] The Tunnel Endpoint Identifier (TEID) information of the third core network element.

[0447] Accordingly, the source RAN can perform data forwarding for the Protocol Data Unit (PDU) session corresponding to the session ID of the terminal under the first core network element. It should be noted that, in this embodiment, the source RAN does not need to wait for the handover response of all sessions to be completed before it can start data forwarding, and can perform data forwarding in parallel for the data of sessions controlled by different first core network elements, which further reduces the service interruption latency during handover.

[0448] Optionally, in the communication device 1600 shown in FIG16, the receiving module may further be used to: receive a fourth message sent by the target RAN, the fourth message being used to notify the terminal to complete the handover from the source RAN to the target RAN. For example, after the handover is completed, the target RAN may send a handover notification (e.g., Nsmf_Handover_Notify) as the fourth message to the first core network element, the handover notification being used to indicate to the first core network element that the terminal has completed the handover.

[0449] The communication device 1600 proposed in the embodiment shown in Figure 16 can realize the communication method shown in Figure 3 and achieve the same technical effect. The relevant parts can be referred to each other, and will not be described in detail here.

[0450] As shown in Figure 17, an embodiment of this application provides a communication device 1700 that can be applied to a target RAN. The communication device 1700 may include: a receiving module 1701, used to receive a first message sent by a first core network element during the process of a terminal switching from a source RAN to a target RAN. The first message is used to request the terminal to be switched to the target RAN. The first core network element is used for session management.

[0451] The first message may carry at least one of the following information:

[0452] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0453] The terminal's session ID;

[0454] The Tunnel Endpoint Identifier (TEID) information of the third core network element.

[0455] Optionally, the communication device 1700 shown in FIG17 may further include: a sending module, configured to send a first confirmation message for the first message to the first core network element.

[0456] The first confirmation message carries at least one of the following information:

[0457] The second terminal identifier is an identifier assigned to the terminal by the target RAN;

[0458] The Tunnel Endpoint Identifier (TEID) information of the target RAN is used by the first core network element and the third core network element to modify the session of the terminal.

[0459] Optionally, in the communication device 1700 shown in FIG17, the receiving module 1701 can also be used to receive the eighth message sent by the second core network element.

[0460] The eighth message carries at least one of the following information:

[0461] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0462] UE context information related to mobility management;

[0463] The session ID of the terminal is the session information of the terminal under the first core network element.

[0464] Optionally, in the communication device 1700 shown in FIG17, the sending module may also be used to: send a sixth confirmation message for the eighth message to the second core network element, wherein the sixth confirmation message carries a second terminal identifier, the second terminal identifier being an identifier assigned to the terminal by the target RAN.

[0465] Optionally, in the communication device 1700 shown in FIG17, the sending module can also be used to: send a fifteenth message to a second core network element, wherein the fifteenth message is used by the second core network element to instruct the source RAN to forward data to the target RAN through an indirect forwarding tunnel, wherein the indirect forwarding tunnel refers to the data transmission tunnel from the source RAN to the third core network element, and then from the third core network element to the target RAN.

[0466] The fifteenth message may carry at least one of the following information:

[0467] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0468] The terminal's session ID;

[0469] The Tunnel Endpoint Identifier (TEID) information of the third core network element.

[0470] Optionally, the communication device 1700 shown in FIG17 may further include:

[0471] The detection module is used to monitor the switching response information of each session of the terminal;

[0472] The sending module can also be used to send a fourteenth message to the second core network element when it is determined that the handover of each session is completed based on the handover response information of each session. The fourteenth message is used to instruct the second core network element to send a handover command about the terminal to the source RAN.

[0473] Optionally, in the communication device 1700 shown in FIG17, the sending module may also be used to: send a seventh message to the first core network element, the seventh message being used to notify the terminal to complete the handover from the source RAN to the target RAN.

[0474] The communication device 1700 proposed in the embodiment shown in Figure 17 can realize the communication method shown in Figure 4 and achieve the same technical effect. The relevant parts can be referred to each other, and will not be described in detail here.

[0475] As shown in Figure 18, an embodiment of this application provides a communication device 1800, which can be applied to a second core network element. The second core network element is used for access and mobility management. The communication device 1800 may include: a sending module 1801, used to send an eighth message to the target RAN during the process of a terminal switching from a source RAN to a target RAN. The eighth message is used to trigger the target RAN to receive a first message sent by a first core network element. The first message is used to request the terminal to switch to the target RAN. The first core network element is used for session management.

[0476] The eighth message carries at least one of the following information:

[0477] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0478] UE context information related to mobility management;

[0479] The session ID of the terminal is the session information of the terminal under the first core network element.

[0480] Optionally, the communication device 1800 shown in FIG18 may further include: a receiving module, configured to receive a sixth confirmation message for the eighth message sent by the target RAN, wherein the sixth confirmation message carries a second terminal identifier, the second terminal identifier being an identifier assigned by the target RAN to the terminal.

[0481] Optionally, in the communication device 1800 shown in FIG18, the receiving module may also be used to: receive a sixteenth message sent by the source RAN, wherein the sixteenth message is used to indicate that the terminal needs to switch from the source RAN to the target RAN.

[0482] The sixteenth message carries at least one of the following information:

[0483] In this embodiment, the first terminal identifier is used to associate the terminal with the second core network element and the corresponding session ID.

[0484] Target RAN ID;

[0485] The terminal's session ID.

[0486] Optionally, the communication device 1800 shown in FIG18 may further include: a selection module for selecting a first core network element. In this embodiment, the first core network element may remain unchanged before and after the switch.

[0487] Optionally, in the communication device 1800 shown in FIG18, the sending module 1801 may also be used to: send a second message to the first core network element, wherein the second message is used to instruct the first core network element that the terminal needs to switch from the source RAN to the target RAN.

[0488] The second message carries at least one of the following information:

[0489] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0490] The user permanent identifier SUPI corresponding to the terminal;

[0491] The ID of the target RAN.

[0492] Optionally, in the communication device 1800 shown in FIG18, the receiving module may also be used to: receive a second confirmation message sent by the first core network element for the second message, wherein the second confirmation message carries the user permanent identifier SUPI corresponding to the terminal.

[0493] Optionally, in the communication device 1800 shown in FIG18, the receiving module may also be used to: receive a fourteenth message sent by the target RAN, wherein the fourteenth message is used to instruct the second core network element to send a handover command about the terminal to the source RAN.

[0494] Optionally, in the communication device 1800 shown in FIG18, the receiving module may also be used to: receive a fifteenth message sent by the target RAN, wherein the fifteenth message is used by the second core network element to instruct the source RAN to forward data to the target RAN through an indirect forwarding tunnel, wherein the indirect forwarding tunnel refers to the data transmission tunnel from the source RAN to the third core network element, and then from the third core network element to the target RAN.

[0495] The fifteenth message may carry at least one of the following information:

[0496] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0497] The terminal's session ID;

[0498] The Tunnel Endpoint Identifier (TEID) information of the third core network element.

[0499] Accordingly, the source RAN can perform data forwarding for the Protocol Data Unit (PDU) session corresponding to the session ID of the terminal under the first core network element. It should be noted that, in this embodiment, the source RAN does not need to wait for the handover response of all sessions to be completed before it can start data forwarding, and can perform data forwarding in parallel for the data of sessions controlled by different first core network elements, which further reduces the service interruption latency during handover.

[0500] Optionally, in the communication device 1800 shown in FIG18, the receiving module may further be used to: receive a fourteenth message sent by the target RAN, wherein the fourteenth message is used to instruct the second core network element to send a handover command about the terminal to the source RAN, and the fourteenth message is sent by the target RAN when it determines that the handover of each session is completed.

[0501] Optionally, in the communication device 1800 shown in FIG18, the transmitting module 1801 may also be used to: send a handover command (e.g., Nran_Handover_Command) to the source RAN, the handover command containing a transparent container from the target RAN to the source RAN.

[0502] Accordingly, the source RAN sends a handover command (e.g., a Handover command) to the terminal, instructing the terminal to synchronize with the target cell. Further, the terminal synchronizes with the target cell. Optionally, the terminal sends a handover confirmation message (e.g., a Handover Confirm) to the target RAN.

[0503] Optionally, in the communication device 1800 shown in FIG18, the receiving module may further be used to: receive a seventeenth message sent by the target RAN, the seventeenth message being used to notify the terminal that the handover from the source RAN to the target RAN has been completed. For example, the target RAN sends a handover notification (e.g., Namf_Handover_Notify) to the AMF, indicating to the AMF that the terminal has completed the handover.

[0504] The communication device 1800 proposed in the embodiment shown in Figure 18 can realize the communication method shown in Figure 5 and achieve the same technical effect. The relevant parts can be referred to each other, and will not be described in detail here.

[0505] As shown in Figure 19, an embodiment of this application provides a communication device 1900, which can be applied to a source RAN. The communication device 1900 may include: a receiving module 1901, used to receive a third message sent by a first core network element, wherein the third message is used to instruct the source RAN to forward data to the target RAN through an indirect forwarding tunnel. The indirect forwarding tunnel refers to a data transmission tunnel from the source RAN to the third core network element, and then from the third core network element to the target RAN. The first core network element is used for session management.

[0506] The third message carries at least one of the following information:

[0507] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0508] The terminal's session ID;

[0509] The tunnel endpoint identifier (TEID) information of the third core network element is used for user plane management.

[0510] Accordingly, the source RAN can perform data forwarding for the Protocol Data Unit (PDU) session corresponding to the session ID of the terminal under the first core network element.

[0511] The communication device 1900 proposed in the embodiment shown in Figure 19 can realize the communication method shown in Figure 6 and achieve the same technical effect. The relevant parts can be referred to each other, and will not be described in detail here.

[0512] As shown in Figure 20, an embodiment of this application provides a communication device 2000, which can be applied to a first core network element. The first core network element is used for session management. The communication device 2000 may include: a receiving module 2001, which is used to receive a fifth message sent by the target RAN during the process of a terminal switching from a source RAN to a target RAN. The fifth message is used to request the terminal to switch to the target RAN. The first core network element is used for session management.

[0513] The fifth message carries at least one of the following information:

[0514] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0515] The second terminal identifier is an identifier assigned to the terminal by the target RAN;

[0516] The terminal's session ID;

[0517] The Tunnel Endpoint Identifier (TEID) information of the target RAN is used by the first core network element and the third core network element to modify the session of the terminal.

[0518] Optionally, the communication device 2000 shown in FIG20 may further include: a selection module for selecting a third core network element, wherein the third core network element is used for user plane management, for example, the third core network element may be a UPF. In this embodiment, the third core network element may remain unchanged before and after the handover.

[0519] Optionally, the communication device 2000 shown in FIG20 may further include: a session modification module for modifying the session with the third core network element.

[0520] Optionally, the communication device 2000 shown in FIG20 may further include: a transmitting module for transmitting a third acknowledgment message for the fifth message to the target RAN.

[0521] The third confirmation message carries at least one of the following information:

[0522] The second terminal identifier is an identifier assigned to the terminal by the target RAN;

[0523] The terminal's session ID;

[0524] The target RAN's tunnel endpoint identifier, T-RAN TEID;

[0525] The Tunnel Endpoint Identifier (TEID) information of the third core network element.

[0526] Optionally, in the communication device 2000 shown in FIG20, the receiving module 2001 may also be used to: receive a sixth message sent by the second core network element, wherein the sixth message is used to instruct the first core network element that the terminal needs to switch from the source RAN to the target RAN.

[0527] The sixth message carries at least one of the following information:

[0528] The first terminal identifier (e.g., S-RAN UE ID) is an identifier assigned to the terminal by the source RAN;

[0529] The second terminal identifier (e.g., T-RAN UE ID) is an identifier assigned to the terminal by the target RAN;

[0530] The user permanent identifier SUPI corresponding to the terminal;

[0531] The ID of the target RAN.

[0532] Optionally, in the communication device 2000 shown in FIG20, the sending module may also be used to: send a fourth confirmation message for the sixth message to the second core network element, wherein the fourth confirmation message carries the user permanent identifier SUPI corresponding to the terminal.

[0533] Optionally, in the communication device 2000 shown in FIG20, the receiving module 2001 may also be used to: receive a seventh message sent by the target RAN, the seventh message being used to notify the terminal to complete the handover from the source RAN to the target RAN.

[0534] The communication device 2000 proposed in the embodiment shown in Figure 20 can realize the communication method shown in Figure 8 and achieve the same technical effect. The relevant parts can be referred to each other, and will not be described in detail here.

[0535] As shown in Figure 21, an embodiment of this application provides a communication device 2100 that can be applied to a target RAN. The communication device 2100 may include: a sending module 2101, used to send a fifth message to a first core network element, the fifth message being used to request the terminal to be switched to the target RAN, and the first core network element being used for session management.

[0536] The fifth message carries at least one of the following information:

[0537] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0538] The second terminal identifier is an identifier assigned to the terminal by the target RAN;

[0539] The terminal's session ID;

[0540] The Tunnel Endpoint Identifier (TEID) information of the target RAN is used by the first core network element and the third core network element to modify the session of the terminal.

[0541] Optionally, the communication device 2100 shown in FIG21 may further include: a receiving module for receiving a third confirmation message sent by the first core network element in response to the fifth message.

[0542] The third confirmation message carries at least one of the following information:

[0543] The second terminal identifier is an identifier assigned to the terminal by the target RAN;

[0544] The terminal's session ID;

[0545] The target RAN's tunnel endpoint identifier, T-RAN TEID;

[0546] The Tunnel Endpoint Identifier (TEID) information of the third core network element.

[0547] Optionally, in the communication device 2100 shown in FIG21, the receiving module can also be used to: receive the eleventh message sent by the second core network element.

[0548] The eleventh message carries at least one of the following information:

[0549] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0550] The ID of the first core network element;

[0551] UE context information related to mobility management;

[0552] The session ID of the terminal is the session information of the terminal under the first core network element.

[0553] Optionally, in the communication device 2100 shown in FIG21, the sending module 2101 may also be used to: send a seventh confirmation message for the eleventh message to the second core network element, wherein the seventh confirmation message carries a second terminal identifier (e.g., T-RAN UE ID), the second terminal identifier being an identifier assigned to the terminal by the target RAN.

[0554] Optionally, in the communication device 2100 shown in FIG21, the sending module 2101 may also be used to: send a twelfth message to a second core network element, wherein the twelfth message is used by the second core network element to instruct the source RAN to forward data to the target RAN through an indirect forwarding tunnel, wherein the indirect forwarding tunnel refers to the data transmission tunnel from the source RAN to the third core network element, and then from the third core network element to the target RAN.

[0555] The twelfth message carries at least one of the following information:

[0556] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0557] The terminal's session ID;

[0558] The Tunnel Endpoint Identifier (TEID) information of the third core network element.

[0559] Optionally, a handover indication message can be sent from the first core network element (such as SMF) to the source RAN. This handover indication message may include the first terminal identifier, the terminal's session ID, and the tunnel endpoint identifier (TEID) information of the third core network element. This handover indication message can be used to instruct the source RAN to start data forwarding through the indirect forwarding tunnel. It is understood that since forwarding through the second core network element (such as AMF) is not required, the problems of detours and low transmission efficiency of handover-related information transmission paths in related technologies can be solved.

[0560] Accordingly, the source RAN performs data forwarding for the terminal's session ID under the first core network element. In this embodiment, the source RAN does not need to wait for all session handover responses to complete before starting data forwarding, and can perform data forwarding in parallel for sessions controlled by different first core network elements, thereby further reducing service interruption latency during handover.

[0561] Optionally, the communication device 2100 shown in FIG21 may further include:

[0562] The monitoring module is used to monitor the switching response information of each session of the terminal;

[0563] Optionally, in the communication device 2100 shown in FIG21, the sending module 2101 may also be used to: when it is determined that the handover of each session is completed according to the handover response information of each session, send a thirteenth message about the terminal to the second core network element, wherein the thirteenth message is used to instruct the second core network element to send a handover command about the terminal to the source RAN.

[0564] Accordingly, the source RAN can further send a handover command (e.g., a Handover command) to the terminal, which instructs the terminal to synchronize with the target cell; the terminal synchronizes with the target cell after receiving the handover command; optionally, the terminal can also send a handover confirmation (e.g., a Handover Confirm) message to the target RAN.

[0565] Optionally, in the communication device 2100 shown in FIG21, the sending module 2101 may further be used to: send a seventeenth message to the second core network element, the seventeenth message being used to notify the terminal that the handover from the source RAN to the target RAN has been completed. For example, the target RAN sends a handover notification (e.g., Namf_Handover_Notify) to the AMF as the seventeenth message, the handover notification being used to indicate to the AMF that the terminal has completed the handover.

[0566] Optionally, in the communication device 2100 shown in FIG21, the sending module 2101 may further be used to: send an eighteenth message to the first core network element, wherein the eighteenth message is used to notify the terminal that the handover from the source RAN to the target RAN has been completed. For example, the target RAN sends a handover notification (e.g., Namf_Handover_Notify) to the SMF as the eighteenth message, which is used to indicate to the AMF that the terminal has completed the handover.

[0567] The communication device 2100 proposed in the embodiment shown in Figure 21 can realize the communication method shown in Figure 9 and achieve the same technical effect. The relevant parts can be referred to each other, and will not be described in detail here.

[0568] As shown in Figure 22, an embodiment of this application provides a communication device 2200, which can be applied to a second core network element. The second core network element is used for access and mobility management. The communication device 2200 may include: a sending module 2201, used to send an eleventh message to the target RAN during the process of a terminal switching from a source RAN to a target RAN. The eleventh message is used to trigger the target RAN to send a fifth message to a first core network element. The fifth message is used to request the terminal to switch to the target RAN. The first core network element is used for session management.

[0569] The eleventh message carries at least one of the following information:

[0570] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0571] The ID of the first core network element, such as the GU SMF ID;

[0572] UE context information related to mobility management;

[0573] The session ID of the terminal is the session information of the terminal under the first core network element.

[0574] Optionally, the communication device 2200 shown in FIG22 may further include: a receiving module, configured to receive a seventh confirmation message for the eleventh message sent by the target RAN, wherein the seventh confirmation message carries a second terminal identifier, the second terminal identifier being an identifier assigned by the target RAN to the terminal.

[0575] Optionally, before sending the eleventh message, the terminal sends a measurement report to the source RAN, the source RAN makes a handover decision, and the source RAN assigns a first terminal identifier (e.g., S-RAN UE ID) to the terminal. Accordingly, in the communication device 2200 shown in FIG22, the receiving module can also be used to: receive the eighteenth message sent by the source RAN, wherein the eighteenth message is used to indicate that the terminal needs to hand over from the source RAN to the target RAN.

[0576] The eighteenth message carries at least one of the following information:

[0577] In this embodiment, the first terminal identifier (e.g., S-RAN UE ID) is used to associate the terminal with the second core network element and the corresponding session ID.

[0578] The ID of the first core network element, such as the GU SMF ID;

[0579] Target RAN ID;

[0580] The terminal's session ID.

[0581] Optionally, the communication device 2200 shown in FIG22 may further include: a selection module, used to select a first core network element according to the eighteenth message before the sending module 2201 sends the eleventh message.

[0582] Optionally, in the communication device 2200 shown in FIG22, the sending module 2201 may also be used to: send a sixth message to the first core network element, wherein the sixth message is used to instruct the first core network element that the terminal needs to switch from the source RAN to the target RAN.

[0583] The sixth message carries at least one of the following information:

[0584] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0585] The second terminal identifier is an identifier assigned to the terminal by the target RAN;

[0586] The user permanent identifier SUPI corresponding to the terminal;

[0587] The ID of the target RAN.

[0588] Optionally, in the communication device 2200 shown in FIG22, the receiving module may also be used to: receive a fourth confirmation message sent by the first core network element for the sixth message, wherein the fourth confirmation message carries the user permanent identifier SUPI corresponding to the terminal.

[0589] Optionally, in the communication device 2200 shown in FIG22, the receiving module may also be used to: receive a twelfth message sent by the target RAN, wherein the twelfth message is used by the second core network element to instruct the source RAN to forward data to the target RAN through an indirect forwarding tunnel, wherein the indirect forwarding tunnel refers to the data transmission tunnel from the source RAN to the third core network element, and then from the third core network element to the target RAN.

[0590] The twelfth message carries at least one of the following information:

[0591] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0592] The terminal's session ID;

[0593] The Tunnel Endpoint Identifier (TEID) information of the third core network element.

[0594] Optionally, in the communication device 2200 shown in FIG22, the receiving module may also be used to: receive a thirteenth message about the terminal sent by the target RAN, wherein the thirteenth message instructs the second core network element to send a handover command about the terminal to the source RAN.

[0595] Optionally, in the communication device 2200 shown in FIG22, the transmitting module 2201 may also be used to: send a handover command about the terminal to the source RAN.

[0596] Accordingly, the source RAN can further send a handover command (e.g., a Handover command) to the terminal, which instructs the terminal to synchronize with the target cell; the terminal synchronizes with the target cell after receiving the handover command; optionally, the terminal can also send a handover confirmation (e.g., a Handover Confirm) message to the target RAN.

[0597] Optionally, in the communication device 2200 shown in FIG22, the receiving module may further be used to: receive a seventeenth message sent by the target RAN, the seventeenth message being used to notify the terminal that the handover from the source RAN to the target RAN has been completed. For example, the target RAN sends a handover notification (e.g., Namf_Handover_Notify) to the AMF as the seventeenth message, which is used to indicate to the AMF that the terminal has completed the handover.

[0598] The communication device 2200 proposed in the embodiment shown in Figure 22 can realize the communication method shown in Figure 10 and achieve the same technical effect. The relevant parts can be referred to each other, and will not be described in detail here.

[0599] As shown in Figure 23, an embodiment of this application provides a communication device 2300, which can be applied to a first core network element. The first core network element is used for session management. The communication device 2300 may include: a receiving module 2301, which is used to receive a tenth message sent by the target RAN. The tenth message is used to instruct the first core network element to control a third core network element to switch the user plane path of the terminal's session from the source RAN to the target RAN. The first core network element is used for session management.

[0600] In some embodiments, the tenth message is sent by the target RAN and the source RAN after modifying the session based on the Xn interface, where the Xn interface is an interface used for communication between the source RAN and the target RAN.

[0601] The tenth message carries at least one of the following information:

[0602] The first terminal identifier (e.g., S-RAN UE ID) is an identifier assigned to the terminal by the source RAN;

[0603] The second terminal identifier (e.g., T-RAN UE ID) is an identifier assigned to the terminal by the target RAN.

[0604] Optionally, the first core network element can perform user plane path switching with the third core network element regarding the terminal. For example, the SMF can perform user plane path switching with the UPF regarding the terminal.

[0605] Optionally, the communication device 2300 shown in FIG23 may further include: a transmitting module for sending a fifth acknowledgment message for the tenth message to the target RAN. For example, the SMF may send a fifth acknowledgment message for the tenth message—a path switch request acknowledgment (e.g., Nsmf_PathSwitchRequestAck) message—to the target RAN.

[0606] The communication device 2300 proposed in the embodiment shown in Figure 23 can realize the communication method shown in Figure 12 and achieve the same technical effect. The relevant parts can be referred to each other, and will not be described in detail here.

[0607] As shown in Figure 24, an embodiment of this application provides a communication device 2400, which can be applied to a target RAN. The communication device 2400 may include: a sending module 2401, which is used to send a tenth message to a first core network element when a terminal switches from a source RAN to a target RAN. The tenth message is used to instruct the first core network element to control a third core network element to switch the user plane path of the terminal's session from the source RAN to the target RAN. The first core network element is used for session management.

[0608] In some embodiments, the tenth message is sent by the target RAN and the source RAN after modifying the session based on the Xn interface, where the Xn interface is an interface used for communication between the source RAN and the target RAN.

[0609] The tenth message carries at least one of the following information:

[0610] The first terminal identifier (e.g., S-RAN UE ID) is an identifier assigned to the terminal by the source RAN;

[0611] The second terminal identifier (e.g., T-RAN UE ID) is an identifier assigned to the terminal by the target RAN.

[0612] Optionally, the communication device 2400 shown in FIG24 may further include: a receiving module, configured to receive a fifth acknowledgment message for the tenth message sent by the first core network element. For example, the SMF may send a fifth acknowledgment message for the tenth message—a path switch request acknowledgment (e.g., Nsmf_PathSwitchRequestAck) message—to the target RAN.

[0613] Optionally, in the communication device 2400 shown in FIG24, the sending module 2401 may also be used to: send a ninth message to a second core network element, wherein the ninth message is used to request that the user plane path of the terminal's session be switched from the source RAN to the target RAN.

[0614] In some embodiments, the ninth message is sent by the target RAN and the source RAN after modifying the session based on the Xn interface, where the Xn interface is an interface used for communication between the source RAN and the target RAN.

[0615] The ninth message carries at least one of the following information:

[0616] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0617] The second terminal identifier is an identifier assigned to the terminal by the target RAN.

[0618] Optionally, in the communication device 2400 shown in FIG. 24, the receiving module can also be used to: receive a ninth acknowledgment message for the ninth message sent by the second core network element. For example, the AMF can send a ninth acknowledgment message for the ninth message—a path switch request acknowledgment (e.g., Nsmf_PathSwitchRequestAck) message—to the target RAN.

[0619] Accordingly, the target RAN can send a UE context release message (e.g., UEContext Release) to the source RAN.

[0620] The communication device 2400 proposed in the embodiment shown in Figure 24 can realize the communication method shown in Figure 13 and achieve the same technical effect. The relevant parts can be referred to each other, and will not be described in detail here.

[0621] As shown in Figure 25, an embodiment of this application provides a communication device 2500, which can be applied to a second core network element. The second core network element is used for access and mobility management. The communication device 2500 may include: a receiving module 2501, which is used to receive a ninth message sent by the target RAN when the terminal switches from the source RAN to the target RAN. The ninth message is used to request that the user plane path of the terminal's session be switched from the source RAN to the target RAN.

[0622] In some embodiments, the ninth message is sent by the target RAN and the source RAN after modifying the session based on the Xn interface, where the Xn interface is an interface used for communication between the source RAN and the target RAN.

[0623] The ninth message carries at least one of the following information:

[0624] The first terminal identifier is an identifier assigned to the terminal by the source RAN;

[0625] The second terminal identifier is an identifier assigned to the terminal by the target RAN.

[0626] Optionally, the communication device 2500 shown in FIG25 may further include: a transmitting module, used for the second core network element to send a ninth confirmation message for the ninth message to the target RAN.

[0627] The communication device 2500 proposed in the embodiment shown in Figure 25 can realize the communication method shown in Figure 14 and achieve the same technical effect. The relevant parts can be referred to each other, and will not be described in detail here.

[0628] This application provides a communication device. As an example, the communication device may be a communication equipment or a component within a communication equipment, such as a chip. The communication equipment may be a terminal, a network-side device, or a server, etc. Exemplarily, the terminal may include, but is not limited to, the type of terminal 11 listed above, and the network-side device may include, but is not limited to, the type of network-side device 12 listed above. This application does not impose specific limitations.

[0629] The communication device includes a receiving module, a transmitting module, and a processing module. These modules can be implemented in software or hardware. When implemented in hardware, the processing module can be implemented by a processor. For example, the processor can include general-purpose processors, special-purpose processors, etc., such as central processing units (CPUs), microprocessors, digital signal processors (DSPs), artificial intelligence (AI) processors, graphics processing units (GPUs), application-specific integrated circuits (ASICs), network processors (NPs), field-programmable gate arrays (FPGAs), or other programmable logic devices, gate circuits, transistors, discrete hardware components, etc. The receiving and transmitting modules can be implemented by a communication interface, which can include one or more of the following: transceivers, pins, circuits, buses, radio frequency units, etc.

[0630] The communication device provided in this application embodiment can implement the various processes implemented in any of the method embodiments in Figures 3 to 6, 8 to 10 and 12 to 14, and achieve the same technical effect. To avoid repetition, it will not be described again here.

[0631] As shown in Figure 26, this application embodiment also provides a communication device 2600, including a processor 2601 and a memory 2602. The memory 2602 stores a program or instructions that can run on the processor 2601. For example, when the communication device 2600 is a terminal, the program or instructions executed by the processor 2601 implement the various steps of the above-described communication method embodiment and achieve the same technical effect. When the communication device 2600 is a network-side device, the program or instructions executed by the processor 2601 implement the various steps of the above-described communication method embodiment and achieve the same technical effect. To avoid repetition, further details are omitted here.

[0632] This application also provides a terminal, including a processor and a communication interface, wherein the communication interface is coupled to the processor, and the processor is used to run programs or instructions to implement the steps executed by the terminal in the method embodiments shown in FIG. 7, FIG. 11, or FIG. 15. This terminal embodiment corresponds to the above-described terminal-side method embodiments, and all implementation processes and methods of the above-described method embodiments can be applied to this terminal embodiment and can achieve the same technical effect. Specifically, FIG. 27 is a schematic diagram of the hardware structure of a terminal implementing an embodiment of this application.

[0633] The terminal 2700 includes, but is not limited to, at least some of the following components: radio frequency unit 2701, network module 2702, audio output unit 2703, input unit 2704, sensor 2705, display unit 2706, user input unit 2707, interface unit 2708, memory 2709, and processor 2710.

[0634] Those skilled in the art will understand that terminal 2700 may also include a power supply (such as a battery) for powering various components. The power supply may be logically connected to processor 2710 through a power management system, thereby enabling functions such as charging, discharging, and power consumption management through the power management system. The terminal structure shown in Figure 27 does not constitute a limitation on the terminal. The terminal may include more or fewer components than shown, or combine certain components, or have different component arrangements, which will not be elaborated here.

[0635] It should be understood that, in this embodiment, the input unit 2704 may include a graphics processor 27041 and a microphone 27042. The graphics processor 27041 processes image data of still images or videos obtained by an image capture device (such as a camera) in video capture mode or image capture mode. The display unit 2706 may include a display panel 27061, which may be configured in the form of a liquid crystal display, an organic light-emitting diode, or the like. The user input unit 2707 includes at least one of a touch panel 27071 and other input devices 27072. The touch panel 27071 is also called a touch screen. The touch panel 27071 may include a touch detection device and a touch controller. Other input devices 27072 may include, but are not limited to, physical keyboards, function keys (such as volume control buttons, power buttons, etc.), trackballs, mice, and joysticks, which will not be described in detail here.

[0636] In this embodiment, after receiving downlink data from the network-side device, the radio frequency unit 2701 can transmit it to the processor 2710 for processing; in addition, the radio frequency unit 2701 can send uplink data to the network-side device. Typically, the radio frequency unit 2701 includes, but is not limited to, antennas, amplifiers, transceivers, couplers, low-noise amplifiers, duplexers, etc.

[0637] The memory 2709 can be used to store software programs or instructions, as well as various data. The memory 2709 may primarily include a first storage area for storing programs or instructions and a second storage area for storing data. The first storage area may store the operating system, application programs or instructions required for at least one function (such as sound playback, image playback, etc.). Furthermore, the memory 2709 may include volatile memory or non-volatile memory. The non-volatile memory may be read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or flash memory. Volatile memory can be random access memory (RAM), static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDRSDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous linked dynamic random access memory (SLDRAM), and direct memory bus RAM (DRRAM). The memory 2709 in this embodiment includes, but is not limited to, these and any other suitable types of memory.

[0638] Processor 2710 may include one or more processing units; optionally, processor 2710 integrates an application processor and a modem processor, wherein the application processor mainly handles operations involving the operating system, user interface, and applications, and the modem processor mainly handles wireless communication signals, such as a baseband processor. It is understood that the aforementioned modem processor may also not be integrated into processor 2710.

[0639] It is understood that the implementation process of each implementation method mentioned in this embodiment can refer to the description of the relevant steps executed by the terminal in the method embodiment shown in Figure 7, Figure 11 or Figure 15, and achieve the same or corresponding technical effect. To avoid repetition, it will not be described again here.

[0640] This application also provides a network-side device, including a processor and a communication interface. The communication interface is coupled to the processor, and the processor is used to run programs or instructions to implement the steps of any of the method embodiments shown in Figures 3 to 6, 8 to 10, and 12 to 14. This network-side device embodiment corresponds to the above-described network-side device method embodiments. All implementation processes and methods of the above-described method embodiments can be applied to this network-side device embodiment and achieve the same technical effects.

[0641] Specifically, this application embodiment also provides a network-side device, which can be a communication device shown in any one of Figures 17, 19, 21, and 24. As shown in Figure 28, the network-side device 2800 includes: an antenna 281, a radio frequency (RF) device 282, a baseband device 283, a processor 284, and a memory 285. The antenna 281 is connected to the RF device 282. In the uplink direction, the RF device 282 receives information through the antenna 281 and sends the received information to the baseband device 283 for processing. In the downlink direction, the baseband device 283 processes the information to be transmitted and sends it to the RF device 282, which then processes the received information and transmits it through the antenna 281.

[0642] The method executed by the network-side device in the above embodiments can be implemented in the baseband device 283, which includes a baseband processor.

[0643] The baseband device 283 may include at least one baseband board, on which multiple chips are disposed, as shown in FIG28. One of the chips is, for example, a baseband processor, which is connected to the memory 285 via a bus interface to call the program or instructions in the memory 285 to execute the network-side device operation shown in the above method embodiment.

[0644] The network-side device may also include a network interface 286, such as a Common Public Radio Interface (CPRI).

[0645] The radio frequency device 282 is used to receive a first message sent by a first core network element during the process of a terminal switching from a source RAN to a target RAN. The first message is used to request the terminal to be switched to the target RAN. The first core network element is used for session management.

[0646] Alternatively, the radio frequency device 282 is used to receive a third message sent by the first core network element, wherein the third message is used to instruct the source RAN to forward data to the target RAN through an indirect forwarding tunnel, wherein the indirect forwarding tunnel refers to the data transmission tunnel from the source RAN to the third core network element and then from the third core network element to the target RAN, and the first core network element is used for session management.

[0647] Alternatively, the radio frequency device 282 is used to send a fifth message to a first core network element, the fifth message being used to request the terminal to be switched to the target RAN, the first core network element being used for session management.

[0648] Alternatively, the radio frequency device 282 is used to send a tenth message to the first core network element when the terminal switches from the source RAN to the target RAN, wherein the tenth message is used to instruct the first core network element to control the third core network element to switch the user plane path of the terminal's session from the source RAN to the target RAN, and the first core network element is used for session management.

[0649] In addition, the network-side device 2800 of this application embodiment also includes: a program or instructions stored in a memory 285 and executable on a processor 284. The processor 284 calls the program or instructions in the memory 285 to execute the methods executed by each module shown in any one of FIG17, FIG19, FIG21 and FIG24, and achieves the same technical effect. To avoid repetition, it will not be described in detail here.

[0650] Specifically, this application embodiment also provides a network-side device. As shown in FIG29, the network-side device 2900 includes: a processor 2901, a network interface 2902, and a memory 2903. The network-side device can be a communication device shown in any one of FIG16, FIG18, FIG20, FIG22, FIG23, and FIG25. The network interface 2902 is, for example, a Common Public Radio Interface (CPRI).

[0651] The network interface 2902 is used to send a first message to the target RAN during the process of a terminal switching from the RAN to the target RAN, wherein the first message is used to request the terminal to be switched to the target RAN.

[0652] Alternatively, network interface 2902 is used to send an eighth message to the target RAN during the process of a terminal switching from a source RAN to a target RAN, wherein the eighth message is used to trigger the target RAN to receive a first message sent by a first core network element, the first message being used to request the terminal to switch to the target RAN, and the first core network element being used for session management.

[0653] Alternatively, network interface 2902 is used to receive a fifth message sent by the target RAN during the process of a terminal switching from a source RAN to a target RAN, wherein the fifth message is used to request the terminal to be switched to the target RAN, and the first core network element is used for session management.

[0654] Alternatively, network interface 2902 is used to send an eleventh message to the target RAN during the process of a terminal switching from a source RAN to a target RAN. The eleventh message is used to trigger the target RAN to send a fifth message to the first core network element. The fifth message is used to request the terminal to switch to the target RAN. The first core network element is used for session management.

[0655] Alternatively, network interface 2902 is used to receive a tenth message sent by the target RAN, wherein the tenth message is used to instruct the first core network element to control the third core network element to switch the user plane path of the terminal's session from the source RAN to the target RAN, and the first core network element is used for session management.

[0656] Alternatively, network interface 2902 is configured to receive a ninth message sent by the target RAN when the terminal switches from the source RAN to the target RAN, wherein the ninth message is configured to request that the user plane path of the terminal's session be switched from the source RAN to the target RAN.

[0657] In addition, the network-side device 2900 of this application embodiment also includes: a program or instructions stored in the memory 2903 and executable on the processor 2901. The processor 2901 calls the program or instructions in the memory 2903 to execute the methods executed by each module shown in any one of FIG16, FIG18, FIG20, FIG22, FIG23 and FIG25, and achieves the same technical effect. To avoid repetition, it will not be described in detail here.

[0658] This application also provides a readable storage medium storing a program or instructions. When the program or instructions are executed by a processor, they implement the various processes of the above-described communication method embodiments and achieve the same technical effects. To avoid repetition, they will not be described again here.

[0659] The processor mentioned above is either the processor in the terminal described in the above embodiments or the processor in the network-side device. The readable storage medium includes computer-readable storage media, such as computer read-only memory (ROM), random access memory (RAM), magnetic disk, or optical disk. In some examples, the readable storage medium may be a non-transient readable storage medium.

[0660] This application embodiment also provides a chip, which includes a processor and a communication interface. The communication interface is coupled to the processor. The processor is used to run programs or instructions to implement the various processes of the above-described communication method embodiments and can achieve the same technical effect. To avoid repetition, it will not be described again here.

[0661] It should be understood that the chip mentioned in the embodiments of this application may also be referred to as a system-on-a-chip, system chip, chip system, or system-on-a-chip, etc.

[0662] This application also provides a computer program / program product, which is stored in a storage medium and executed by at least one processor to implement the various processes of the above-described communication method embodiments, and can achieve the same technical effect. To avoid repetition, it will not be described again here.

[0663] This application also provides a wireless communication system, including: a first core network device, a target RAN, a second core network device, and a source RAN. The first core network device can be used to perform the steps of the method shown in FIG3, the target RAN can be used to perform the steps of the method shown in FIG4, the second core network device can be used to perform the steps of the method shown in FIG5, and the source RAN can be used to perform the steps of the method shown in FIG6.

[0664] This application also provides a wireless communication system, including: a first core network device, a target radio access network (RAN), and a second core network device. The first core network device can be used to perform the steps of the method shown in FIG8, the target RAN can be used to perform the steps of the method shown in FIG9, and the second core network device can be used to perform the steps of the method shown in FIG10.

[0665] This application also provides a wireless communication system, including: a first core network device, a target radio access network (RAN), and a second core network device. The first core network device can be used to perform the steps of the method shown in FIG12, the target RAN can be used to perform the steps of the method shown in FIG13, and the second core network device can be used to perform the steps of the method shown in FIG14.

[0666] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0667] From the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of computer software products plus necessary general-purpose hardware platforms, and of course, they can also be implemented by hardware. The computer software product is stored in a storage medium (such as ROM, RAM, magnetic disk, optical disk, etc.), and the computer software product includes several instructions to cause the terminal or network-side device to execute the methods described in the various embodiments of this application.

[0668] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other implementations under the guidance of this application without departing from the spirit and scope of the claims. All of these implementations are within the protection scope of this application.

Claims

1. A communication method, the method comprising: During the process of a terminal switching from the source radio access network (RAN) to the target RAN, a first core network element sends a first message to the target RAN. The first message is used to request the terminal to switch to the target RAN, and the first core network element is used for session management.

2. The method according to claim 1, wherein, The first message carries at least one of the following information: The first terminal identifier is an identifier assigned to the terminal by the source RAN; The terminal's session ID; The tunnel endpoint identifier (TEID) information of the third core network element.

3. The method according to claim 1 or 2, wherein, Also includes: The first core network element receives a first acknowledgment message from the target RAN in response to the first message, wherein the first acknowledgment message carries at least one of the following information: The second terminal identifier, wherein the first terminal identifier is an identifier assigned to the terminal by the target RAN; The target RAN's tunnel endpoint identifier (TEID) information is used by the first core network element and the third core network element to modify the session regarding the terminal.

4. The method according to any one of claims 1-3, wherein, Also includes: The first core network element receives a second message sent by the second core network element, wherein the second message is used to instruct the first core network element that the terminal needs to switch from the source RAN to the target RAN.

5. The method according to claim 4, wherein, The second message carries at least one of the following information: The first terminal identifier is an identifier assigned to the terminal by the source RAN; The user permanent identifier SUPI corresponding to the terminal; The ID of the target RAN.

6. The method according to claim 4 or 5, wherein, Also includes: The first core network element sends a second confirmation message to the second core network element in response to the second message. The second confirmation message carries the user permanent identifier SUPI corresponding to the terminal.

7. The method according to any one of claims 1-6, wherein, Also includes: The first core network element sends a third message to the source RAN, wherein the third message is used to instruct the source RAN to forward data to the target RAN through an indirect forwarding tunnel, and the indirect forwarding tunnel refers to the data transmission tunnel from the source RAN to the third core network element, and then from the third core network element to the target RAN.

8. The method according to claim 7, wherein, The third message carries at least one of the following information: The first terminal identifier is an identifier assigned to the terminal by the source RAN; The terminal's session ID; The tunnel endpoint identifier (TEID) information of the third core network element.

9. The method according to any one of claims 1-8, wherein, Also includes: The first core network element receives a fourth message sent by the target RAN, the fourth message being used to notify the terminal to complete the handover from the source RAN to the target RAN.

10. A communication method, the method comprising: During the process of a terminal switching from the source radio access network (RAN) to the target RAN, the first core network element receives a fifth message sent by the target RAN. The fifth message is used to request the terminal to switch to the target RAN, and the first core network element is used for session management.

11. The method according to claim 10, wherein, The fifth message carries at least one of the following information: The first terminal identifier is an identifier assigned to the terminal by the source RAN; The second terminal identifier is an identifier assigned to the terminal by the target RAN; The terminal's session ID; The target RAN's tunnel endpoint identifier (TEID) information is used by the first core network element and the third core network element to modify the session regarding the terminal.

12. The method according to claim 10 or 11, wherein, Also includes: The first core network element sends a third confirmation message to the target RAN in response to the fifth message, wherein the third confirmation message carries at least one of the following information: The second terminal identifier is an identifier assigned to the terminal by the target RAN; The terminal's session ID; The target RAN's tunnel endpoint identifier (TEID) information; The tunnel endpoint identifier (TEID) information of the third core network element.

13. The method according to any one of claims 10-12, wherein, Also includes: The first core network element receives a sixth message sent by the second core network element, wherein the sixth message is used to instruct the first core network element that the terminal needs to switch from the source RAN to the target RAN.

14. The method according to claim 13, wherein, The sixth message carries at least one of the following information: The first terminal identifier is an identifier assigned to the terminal by the source RAN; The second terminal identifier is an identifier assigned to the terminal by the target RAN; The user permanent identifier SUPI corresponding to the terminal; The ID of the target RAN.

15. The method according to claim 13 or 14, wherein, Also includes: The first core network element sends a fourth confirmation message to the second core network element in response to the sixth message. The fourth confirmation message carries the user permanent identifier SUPI corresponding to the terminal.

16. The method according to any one of claims 10-15, wherein, Also includes: The first core network element receives a seventh message sent by the target RAN, the seventh message being used to notify the terminal to complete the handover from the source RAN to the target RAN.

17. A communication method, the method comprising: When a terminal switches from a source radio access network (RAN) to a target RAN, a first core network element receives a tenth message sent by the target RAN. The tenth message is used to instruct the first core network element to control a third core network element to switch the user plane path of the terminal's session from the source RAN to the target RAN. The first core network element is used for session management.

18. The method according to claim 17, wherein, Also includes: The first core network element sends a fifth confirmation message to the target RAN in response to the tenth message.

19. The method according to claim 17 or 18, wherein, The tenth message is sent by the target RAN and the source RAN after modifying the session based on the Xn interface.

20. The method according to any one of claims 17-19, wherein, The tenth message carries at least one of the following information: The first terminal identifier is an identifier assigned to the terminal by the source RAN; The second terminal identifier is an identifier assigned to the terminal by the target RAN.

21. A communication method, the method comprising: During the process of a terminal switching from a source radio access network (RAN) to a target RAN, the target RAN receives a first message sent by a first core network element. The first message is used to request the terminal to be switched to the target RAN. The first core network element is used for session management.

22. The method according to claim 21, wherein, The first message carries at least one of the following information: The first terminal identifier is an identifier assigned to the terminal by the source RAN; The terminal's session ID; The tunnel endpoint identifier (TEID) information of the third core network element.

23. The method according to claim 21 or 22, wherein, Also includes: The target RAN sends a first confirmation message to the first core network element in response to the first message, wherein the first confirmation message carries at least one of the following information: The second terminal identifier is an identifier assigned to the terminal by the target RAN; The target RAN's tunnel endpoint identifier (TEID) information is used by the first core network element and the third core network element to modify the session regarding the terminal.

24. The method according to any one of claims 21-23, wherein, The method further includes: The target RAN receives an eighth message sent by the second core network element, the eighth message carrying at least one of the following information: The first terminal identifier is an identifier assigned to the terminal by the source RAN; UE context information related to mobility management; The session ID of the terminal is the session information of the terminal under the first core network element.

25. The method according to claim 24, wherein, Also includes: The target RAN sends a sixth confirmation message to the second core network element in response to the eighth message, wherein the sixth confirmation message carries a second terminal identifier, which is an identifier assigned to the terminal by the target RAN.

26. The method according to any one of claims 21-25, wherein, Also includes: The target RAN monitors the handover response information of each session of the terminal; When the target RAN determines that the handover of each session is complete based on the handover response information of each session, it sends a fourteenth message to the second core network element, wherein the fourteenth message is used to instruct the second core network element to send a handover command about the terminal to the source RAN.

27. The method according to any one of claims 21-26, wherein, Also includes: The target RAN sends a seventh message to the first core network element, the seventh message being used to notify the terminal to complete the handover from the source RAN to the target RAN.

28. A communication method, the method comprising: During the process of a terminal switching from the source radio access network (RAN) to the target RAN, the target RAN sends a fifth message to the first core network element. The fifth message is used to request the terminal to be switched to the target RAN. The first core network element is used for session management.

29. The method according to claim 28, wherein, The fifth message carries at least one of the following information: The first terminal identifier is an identifier assigned to the terminal by the source RAN; The second terminal identifier is an identifier assigned to the terminal by the target RAN; The terminal's session ID; The target RAN's tunnel endpoint identifier (TEID) information is used by the first core network element and the third core network element to modify the session regarding the terminal.

30. The method according to claim 28 or 29, wherein, Also includes: The target RAN receives a third confirmation message for the fifth message sent by the first core network element, wherein the third confirmation message carries at least one of the following information: The second terminal identifier is an identifier assigned to the terminal by the target RAN; The terminal's session ID; The target RAN's tunnel endpoint identifier (TEID) information; The tunnel endpoint identifier (TEID) information of the third core network element.

31. The method according to any one of claims 29-31, wherein, Also includes: The target RAN receives the eleventh message sent by the second core network element, wherein the eleventh message carries at least one of the following information: The first terminal identifier is an identifier assigned to the terminal by the source RAN; UE context information related to mobility management; The ID of the first core network element; The session ID of the terminal is the session information of the terminal under the first core network element.

32. The method according to claim 31, wherein, Also includes: The target RAN sends a seventh confirmation message to the second core network element in response to the eleventh message, wherein the seventh confirmation message carries a second terminal identifier, which is an identifier assigned to the terminal by the target RAN.

33. The method according to any one of claims 28-32, wherein, Also includes: The target RAN sends a twelfth message to the second core network element, wherein the twelfth message is used by the second core network element to instruct the source RAN to forward data to the target RAN through an indirect forwarding tunnel, wherein the indirect forwarding tunnel refers to the data transmission tunnel from the source RAN to the third core network element, and then from the third core network element to the target RAN.

34. The method according to claim 33, wherein, The twelfth message carries at least one of the following information: The first terminal identifier is an identifier assigned to the terminal by the source RAN; The terminal's session ID; The tunnel endpoint identifier (TEID) information of the third core network element.

35. The method according to any one of claims 28-34, wherein, Also includes: The target RAN monitors the handover response information of each session of the terminal; When the target RAN determines that the handover of each session is completed based on the handover response information of each session, it sends a thirteenth message about the terminal to the second core network element, wherein the thirteenth message is used to instruct the second core network element to send a handover command about the terminal to the source RAN.

36. The method according to any one of claims 28-35, wherein, Also includes: After the handover is completed, the target RAN sends an eighteenth message to the first core network element, wherein the eighteenth message is used to notify the terminal that the handover from the source RAN to the target RAN has been completed.

37. A communication method, the method comprising: When a terminal switches from a source radio access network (RAN) to a target RAN, the target RAN sends a tenth message to the first core network element. The tenth message is used to instruct the first core network element to control a third core network element to switch the user plane path of the terminal's session from the source RAN to the target RAN. The first core network element is used for session management.

38. The method according to claim 37, wherein, Also includes: The target RAN receives a fifth confirmation message for the tenth message sent by the first core network element.

39. The method according to claim 37 or 38, wherein, The tenth message is sent after the target RAN and the source RAN complete the session handover based on the Xn interface.

40. The method according to any one of claims 37-39, wherein, The tenth message carries at least one of the following information: The first terminal identifier is an identifier assigned to the terminal by the source RAN; The second terminal identifier is an identifier assigned to the terminal by the target RAN.

41. The method according to any one of claims 37-40, wherein, Also includes: The target RAN sends a ninth message to the second core network element, wherein the ninth message is used to request that the user plane path of the terminal's session be switched from the source RAN to the target RAN.

42. The method according to claim 41, wherein, Also includes: The target RAN receives a ninth confirmation message for the ninth message sent by the second core network element.

43. The method according to claim 41 or 42, wherein, The ninth message carries at least one of the following information: The first terminal identifier is an identifier assigned to the terminal by the source RAN; The second terminal identifier is an identifier assigned to the terminal by the target RAN.

44. A communication method, the method comprising: During the process of a terminal switching from the source radio access network (RAN) to the target RAN, the second core network element sends an eighth message to the target RAN. The eighth message is used to trigger the target RAN to receive a first message sent by the first core network element. The first message is used to request the terminal to switch to the target RAN. The first core network element is used for session management.

45. The method according to claim 44, wherein, in, The eighth message carries at least one of the following information: The first terminal identifier is an identifier assigned to the terminal by the source RAN; UE context information related to mobility management; The session ID of the terminal is the session information of the terminal under the first core network element.

46. ​​The method according to claim 44 or 45, wherein, Also includes: The second core network element receives a sixth confirmation message for the eighth message sent by the target RAN, wherein the sixth confirmation message carries a second terminal identifier, which is an identifier assigned to the terminal by the target RAN.

47. The method according to any one of claims 44-46, wherein, Also includes: The second core network element sends a second message to the first core network element, wherein the second message is used to instruct the first core network element that the terminal needs to switch from the source RAN to the target RAN.

48. The method according to claim 47, wherein, The second message carries at least one of the following information: The first terminal identifier is an identifier assigned to the terminal by the source RAN; The user permanent identifier SUPI corresponding to the terminal; The ID of the target RAN.

49. The method according to claim 47 or 48, wherein, Also includes: The second core network element receives a second confirmation message sent by the first core network element in response to the second message. The second confirmation message carries the user permanent identifier SUPI corresponding to the terminal.

50. The method according to any one of claims 44-49, wherein, Also includes: The second core network element receives the fourteenth message sent by the target RAN, wherein the fourteenth message is used to instruct the second core network element to send a handover command about the terminal to the source RAN.

51. A communication method, the method comprising: During the process of a terminal switching from the source radio access network (RAN) to the target RAN, the second core network element sends an eleventh message to the target RAN. The eleventh message is used to trigger the target RAN to send a fifth message to the first core network element. The fifth message is used to request the terminal to switch to the target RAN. The first core network element is used for session management.

52. The method according to claim 51, wherein, in, The eleventh message carries at least one of the following information: The first terminal identifier is an identifier assigned to the terminal by the source RAN; The ID of the first core network element; UE context information related to mobility management; The session ID of the terminal is the session information of the terminal under the first core network element.

53. The method according to claim 51 or 52, wherein, Also includes: The second core network element receives a seventh confirmation message for the eleventh message sent by the target RAN, wherein the seventh confirmation message carries a second terminal identifier, which is an identifier assigned to the terminal by the target RAN.

54. The method according to any one of claims 51-53, wherein, Also includes: The second core network element sends a sixth message to the first core network element, wherein the sixth message is used to instruct the first core network element that the terminal needs to switch from the source RAN to the target RAN.

55. The method according to claim 54, wherein, The sixth message carries at least one of the following information: The first terminal identifier is an identifier assigned to the terminal by the source RAN; The second terminal identifier is an identifier assigned to the terminal by the target RAN; The user permanent identifier SUPI corresponding to the terminal; The ID of the target RAN.

56. The method according to claim 54 or 55, wherein, Also includes: The second core network element receives a fourth confirmation message sent by the first core network element in response to the sixth message, the fourth confirmation message carrying the user permanent identifier SUPI corresponding to the terminal.

57. The method according to any one of claims 51-56, wherein, The method further includes: The second core network element receives the twelfth message sent by the target RAN, wherein the twelfth message is used by the second core network element to instruct the source RAN to forward data to the target RAN through an indirect forwarding tunnel, wherein the indirect forwarding tunnel refers to the data transmission tunnel from the source RAN to the third core network element, and then from the third core network element to the target RAN.

58. The method according to claim 57, wherein, The twelfth message carries at least one of the following information: The first terminal identifier is an identifier assigned to the terminal by the source RAN; The terminal's session ID; The tunnel endpoint identifier (TEID) information of the third core network element.

59. The method according to any one of claims 51-58, wherein, The method further includes: The second core network element receives a thirteenth message about the terminal sent by the target RAN, wherein the thirteenth message instructs the second core network element to send a handover command about the terminal to the source RAN.

60. A communication method, the method comprising: When a terminal switches from the source radio access network (RAN) to the target RAN, the second core network element receives a ninth message sent by the target RAN, wherein the ninth message is used to request that the user plane path of the terminal's session be switched from the source RAN to the target RAN.

61. The method according to claim 60, wherein, The ninth message is sent after the target RAN and the source RAN complete the session handover of the terminal based on the Xn interface.

62. The method according to claim 60 or 61, wherein, The method further includes: The second core network element sends a ninth confirmation message to the target RAN in response to the ninth message.

63. The method according to any one of claims 60-62, wherein, The ninth message carries at least one of the following information: The first terminal identifier is an identifier assigned to the terminal by the source RAN; The second terminal identifier is an identifier assigned to the terminal by the target RAN.

64. A communication method, the method comprising: During the process of a terminal switching from a source radio access network (RAN) to a target RAN, the source RAN receives a third message sent by a first core network element. The third message is used to instruct the source RAN to forward data to the target RAN through an indirect forwarding tunnel. The indirect forwarding tunnel refers to the data transmission tunnel from the source RAN to the third core network element and then from the third core network element to the target RAN. The first core network element is used for session management.

65. The method according to claim 64, wherein, The third message carries at least one of the following information: The first terminal identifier is an identifier assigned to the terminal by the source RAN; The terminal's session ID; The tunnel endpoint identifier (TEID) information of the third core network element.

66. A communication device applied to a first core network element, the device comprising: The sending module is used to send a first message to the target RAN during the process of a terminal switching from the source radio access network RAN ​​to the target RAN, wherein the first message is used to request the terminal to switch to the target RAN, and the first core network element is used for session management.

67. A communication device applied to a first core network element, the device comprising: The receiving module is configured to receive a fifth message sent by the target RAN during the process of the terminal switching from the source radio access network RAN ​​to the target RAN, wherein the fifth message is used to request the terminal to switch to the target RAN, and the first core network element is used for session management.

68. A communication device applied to a first core network element, the device comprising: The receiving module is configured to receive a tenth message sent by the target RAN when the terminal switches from the source radio access network RAN ​​to the target RAN. The tenth message is configured to instruct the first core network element to control the third core network element to switch the user plane path of the terminal's session from the source RAN to the target RAN. The first core network element is used for session management.

69. A communication apparatus applied to a target radio access network (RAN), the apparatus comprising: The receiving module is used to receive a first message sent by a first core network element during the process of a terminal switching from a source RAN to the target RAN. The first message is used to request the terminal to be switched to the target RAN. The first core network element is used for session management.

70. A communication apparatus applied to a target radio access network (RAN), the apparatus comprising: The sending module is used to send a fifth message to a first core network element during the process of a terminal switching from a source RAN to the target RAN. The fifth message is used to request the terminal to switch to the target RAN. The first core network element is used for session management.

71. A communication apparatus applied to a target radio access network (RAN), the apparatus comprising: The sending module sends a tenth message to the first core network element when the terminal switches from the source RAN to the target RAN. The tenth message is used to instruct the first core network element to control the third core network element to switch the user plane path of the terminal's session from the source RAN to the target RAN. The first core network element is used for session management.

72. A communication device applied to a second core network element, the device comprising: The sending module is used to send an eighth message to the target RAN during the process of a terminal switching from a source radio access network (RAN) to a target RAN. The eighth message is used to trigger the target RAN to receive a first message sent by a first core network element. The first message is used to request the terminal to switch to the target RAN. The first core network element is used for session management.

73. A communication device applied to a second core network element, the device comprising: The sending module is used to send an eleventh message to the target RAN during the process of the terminal switching from the source radio access network RAN ​​to the target RAN. The eleventh message is used to trigger the target RAN to send a fifth message to the first core network element. The fifth message is used to request the terminal to switch to the target RAN. The first core network element is used for session management.

74. A communication device applied to a second core network element, the device comprising: The receiving module is configured to receive a ninth message sent by the target RAN when the terminal switches from the source radio access network RAN ​​to the target RAN, wherein the ninth message is used to request that the user plane path of the terminal's session be switched from the source RAN to the target RAN.

75. A communication apparatus applied to a source radio access network (RAN), the apparatus comprising: The receiving module is used to receive a third message sent by a first core network element during the process of a terminal switching from the source RAN to the target RAN. The third message is used to instruct the source RAN to forward data to the target RAN through an indirect forwarding tunnel. The indirect forwarding tunnel refers to the data transmission tunnel from the source RAN to the third core network element and then from the third core network element to the target RAN. The first core network element is used for session management.

76. A network-side device comprising a processor and a memory, the memory storing a program or instructions executable on the processor, the program or instructions, when executed by the processor, implementing the steps of the communication method as claimed in any one of claims 1 to 65.

77. A readable storage medium storing a program or instructions that, when executed by a processor, implement the communication method as described in any one of claims 1 to 65.

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