Communication method, apparatus, and system, chip module, and storage medium

Abstract

A communication method, apparatus, and system, a chip module, and a storage medium. The method comprises: a session management function network element determines that a terminal is in a radio resource control (RRC) inactive state; on the basis of the terminal being in the RRC inactive state, the session management function network element sends first indication information to a user plane function network element, the first indication information being used for storing downlink data to be sent to the terminal; the user plane function network element receives the downlink data to be sent to the terminal, and stores the downlink data on the basis of the first indication information; and, after the terminal enters a connected state, the user plane function network element sends the stored downlink data to the terminal. The user plane function network element can promptly send the stored downlink data to the terminal without waiting for timeout-based retransmission of the downlink data, thereby reducing a service delay in a scenario in which the terminal is in the RRC inactive state and cannot be successfully paged on the basis of a RAN notification area.

Description

Communication method, device, system, chip module and storage medium

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office of China on February 8, 2024, with application number 202410179114.0 and invention name “Communication method, device, system, chip module and storage medium”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of communication technologies, and in particular to communication methods, devices, systems, chip modules, and storage media. Background Art

[0003] The standard protocols for the fifth-generation (5G) mobile communication system define a new radio resource control (RRC) inactive state, compared to the long-term evolution (LTE) system. In the RRC inactive state, the RRC connection between the terminal and the radio access network (RAN) is disconnected, but the communication link established for the terminal between the RAN and the core network remains connected.

[0004] Generally, when the RRC is inactive and the core network needs to send downlink data to a terminal, such as when a call is received from the calling terminal or when the core network needs to transmit data to the terminal, the network will first page the terminal within the radio access network notification area (RAN) to which the UE belongs. If the terminal cannot be successfully paged within the RAN notification area, the network will trigger a core network paging method with a larger paging range than the RAN notification area to page the terminal. The terminal will eventually reconnect to the network by executing a service request process.

[0005] However, in actual applications, it is found that after the terminal reconnects to the network based on the core network paging method, it still needs to wait for a long time to receive the downlink data, and the service delay problem needs to be improved. Summary of the Invention

[0006] The present application provides a communication method, device, system, chip module and storage medium to reduce service delay in a scenario where a terminal is in an RRC inactive state and cannot be successfully paged based on a RAN notification area.

[0007] In the first aspect, the present application provides a communication method, which is applied to a third network element (e.g., a user plane function network element), and the method includes: receiving first indication information, the first indication information being used to store downlink data sent to a terminal, the terminal being in an inactive state of radio resource control RRC; receiving downlink data sent to the terminal; storing the downlink data based on the first indication information; and sending the stored downlink data to the terminal after the terminal enters a connected state.

[0008] With the communication method provided in the embodiments of the present application, when a terminal is in an RRC inactive state, the third network element stores downlink data to be sent to the terminal. After the terminal enters a connected state, the third network element can immediately send the stored downlink data to the terminal without waiting for retransmission due to a timeout. This reduces service latency in scenarios where the terminal is in an RRC inactive state and cannot be successfully paged based on the RAN notification area.

[0009] In some possible implementations, sending the stored downlink data to the terminal after the terminal enters a connected state includes: after the paging result of the first access network device paging the terminal is a paging failure and the terminal enters a connected state, sending the stored downlink data to the terminal, the first access network device being the access network device that last served the terminal.

[0010] In some possible implementations, storing the downlink data based on the first indication information includes: storing the downlink data based on the first indication information when the paging result of the first access network device paging the terminal is a paging failure, and the first access network device is the access network device that last served the terminal.

[0011] By adopting this method, downlink data is stored based on the first indication information only when the paging result of the first access network device paging the terminal is a paging failure. This can reduce the service delay in the scenario where the RRC is in an inactive state and the terminal cannot be successfully paged based on the RAN notification area, while further reducing unnecessary storage tasks for the downlink data, improving the utilization rate of the stored downlink data, and reducing unnecessary storage overhead.

[0012] In some possible implementations, the first indication information indicates the storage of downlink data sent to the terminal, or indicates that the terminal is in an RRC inactive state, or indicates that the paging result of the first access network device paging the terminal is a paging failure, and the first access network device is the access network device that last served the terminal.

[0013] In some possible implementations, the receiving the first indication information includes: receiving the first indication information in a session establishment process or a session modification process of the terminal.

[0014] The first indication information comes from a first network element (for example, the first network element is an access and mobility management network element) or from a second network element (for example, the second network element is a session management function network element).

[0015] In this way, the first indication information can be integrated into the session establishment process or the session modification process, which has good compatibility, and can improve the coupling degree between the communication method of this solution and the existing process, thereby reducing the engineering workload.

[0016] In some possible implementations, the downlink data is voice service data.

[0017] In some possible implementations, the method further includes: setting a timer, deleting the stored downlink data after the timer times out, the timer being related to a first duration and / or a second duration, the first duration being the timeout retransmission duration of the downlink data, and the second duration being the duration required for the terminal to migrate from the RRC inactive state to the idle state and then to the connected state. It should be noted that if the duration of the timer is related to the second duration, then before deleting the downlink data, it is also necessary to determine whether the downlink data has been sent to the terminal. If not, it will not be deleted. If it has been sent, it can be deleted.

[0018] In this manner, the downlink data is deleted after the timer expires. On the one hand, if the timer duration is related to the first duration, the downlink data is deleted after the downlink data is retransmitted, thereby updating the downlink data information. On the other hand, if the timer duration is related to the second duration, the downlink data is deleted after it has been transmitted to the terminal, thereby reducing data storage overhead.

[0019] In some possible implementations, the method further includes: after the terminal enters a connected state, receiving second indication information, the second indication information being used to delete the downlink data after sending the downlink data to the terminal, and / or for no longer storing the downlink data sent to the terminal; based on the second indication information, deleting the downlink data after sending the downlink data to the terminal, and / or determining that the downlink data sent to the terminal is no longer stored.

[0020] In some possible implementations, the second indication information indicates one or more of deleting the downlink data after sending the downlink data to the terminal, indicating that the downlink data sent to the terminal is no longer stored, or indicating that the terminal is in a connected state.

[0021] By adopting this method, after the third network element has sent the downlink data to the terminal, the downlink data is deleted, and / or, when the terminal enters the connected state and can directly send the downlink data to the terminal based on the first access network device, the downlink data sent to the terminal is no longer stored, which can improve the utilization rate of the stored downlink data and avoid unnecessary storage overhead.

[0022] In the second aspect, the present application provides a communication method applied to a second network element, the method comprising: determining that a terminal is in a radio resource control RRC inactive state; based on the terminal being in an RRC inactive state, sending a first indication information to a third network element, the first indication information being used to store downlink data sent to the terminal.

[0023] Using the communication method provided in an embodiment of the present application, when a terminal is in an RRC inactive state, a second network element sends first indication information to a third network element, causing the third network element to store downlink data to be sent to the terminal. Thus, after the terminal enters a connected state, the third network element can immediately send the stored downlink data to the terminal without waiting for the downlink data to time out and be retransmitted, thereby reducing service latency in scenarios where the terminal is in an RRC inactive state and cannot be successfully paged based on the RAN notification area.

[0024] In some possible implementations, the sending of the first indication information to the third network element based on the terminal being in an RRC inactive state includes: when the paging result of the first access network device paging the terminal is a paging failure, sending the first indication information to the third network element, and the first access network device is the access network device that last served the terminal.

[0025] In this manner, the second network element sends the first indication information to the third network element only when it determines that the terminal is in an RRC inactive state and that the paging result of the terminal paging based on the first access network device is a paging failure. On the one hand, after the terminal enters the RRC inactive state, if the third network element has stored the downlink data, it can directly send the stored downlink data to the terminal, thereby reducing the probability that the third network element needs to wait for the retransmission of the downlink data before sending the downlink data to the terminal after the terminal enters the RRC inactive state, switches to the RRC idle state, and finally enters the RRC connected state, thereby reducing the service delay in this scenario. On the other hand, it can reduce the problem of invalid storage of the downlink data stored by the third network element that will not be used when the terminal is in the RRC inactive state and the terminal can be paged based on the first access network device, further improve the utilization rate of the stored downlink data, reduce unnecessary communication transmission of the first indication information, and alleviate the data storage pressure of the third network element.

[0026] In some possible implementations, the first indication information indicates the storage of downlink data sent to the terminal, or indicates that the terminal is in an RRC inactive state, or indicates that the paging result of the first access network device paging the terminal is a paging failure, and the first access network device is the access network device that last served the terminal.

[0027] In some possible implementations, the sending of first indication information to a third network element based on the terminal being in an RRC inactive state includes: in a session establishment process or a session modification process of the terminal, sending the first indication information to the third network element based on the terminal being in an RRC inactive state.

[0028] In some possible implementations, determining that the terminal is in a radio resource control (RRC) inactive state includes: sending a first subscription request to an access and mobility management function network element, wherein the first subscription request is used to request notification of the terminal entering the RRC inactive state; and receiving a first notification message from the access and mobility management function network element, wherein the first notification message is used to instruct the terminal to enter the RRC inactive state.

[0029] In some possible implementations, the first subscription request is also used to request notification of the terminal to enter a connected state, and the method further includes: receiving a second notification message from the access and mobility management function network element, the second notification message being used to instruct the terminal to enter a connected state; sending a second indication information to the third network element, the second indication information being used to instruct the downlink data to be deleted after being sent to the terminal, and / or instructing that the downlink data sent to the terminal is no longer stored.

[0030] In some possible implementations, the second indication information indicates one or more of deleting the downlink data after sending the downlink data to the terminal, indicating that the downlink data sent to the terminal is no longer stored, or indicating that the terminal is in a connected state.

[0031] In some possible implementations, the downlink data is voice service data.

[0032] In some possible implementations, sending the first subscription request to the access and mobility management function network element includes: sending the first subscription request to the access and mobility management function network element in a session establishment process of the terminal.

[0033] In a third aspect, the present application provides a communication method, applied to a first network element and / or a second network element, the method comprising: receiving a first subscription request, the first subscription request being used to request notification of a terminal entering a radio resource control (RRC) inactive state; when the terminal enters the RRC inactive state, sending a first notification message based on the first subscription request, the first notification message being used to instruct the terminal to enter the RRC inactive state.

[0034] The final destination of the first notification message is the third network element, so that the third network element stores the downlink data of the terminal based on the first notification message.

[0035] As an example, the second network element may enter the RRC inactive state to subscribe to the terminal of the first network element, and send the first indication information in any possible implementation method of the above-mentioned first aspect or second aspect to the third network element based on the first notification message.

[0036] As another example, the third network element may subscribe to the first network element or the second network element to allow the terminal to enter the RRC inactive state, and after receiving the above-mentioned first notification message, determine to store the downlink data sent to the terminal based on the terminal entering the RRC inactive state.

[0037] Therefore, after the terminal enters the connected state, the third network element can send the stored downlink data to the terminal as soon as possible without waiting for the downlink data to time out and be retransmitted, thereby reducing the service delay in the scenario where the terminal is in an RRC inactive state and cannot successfully page the terminal based on the RAN notification area.

[0038] In some possible implementations, the first subscription request is also used to request notification of the terminal entering a connected state, and the method further includes: when the terminal enters a connected state, sending a second notification message based on the first subscription request, and the second notification message is used to indicate that the terminal enters a connected state.

[0039] In a fourth aspect, the present application provides a communication method, applied to a third network element, the method including: receiving a second subscription request, the second subscription request being used to request notification of receipt of downlink data sent to a terminal, the terminal being in an RRC inactive state; receiving downlink data sent to the terminal; sending a third notification message based on the second subscription request, the third notification message being used to indicate receipt of downlink data sent to the terminal; receiving third indication information, the third indication information being used to store the downlink data; storing the downlink data based on the third indication information; and sending the stored downlink data to the terminal after the terminal enters a connected state.

[0040] Using the communication method provided in an embodiment of the present application, the second network element sends a second subscription request to the third network element based on the terminal being in an RRC inactive state. In response to receiving a third notification message from the third network element, the second network element sends the third indication information to the third network element. After receiving downlink data from the terminal, the third network element stores the received downlink data based on the third indication information. Thus, in a scenario where the terminal switches from an RRC inactive state to an idle state and ultimately enters a connected state, the third network element can immediately send the stored downlink data to the terminal without waiting for retransmission of the downlink data, thereby reducing service latency.

[0041] In some possible implementations, sending the stored downlink data to the terminal after the terminal enters a connected state includes: after the paging result of the first access network device paging the terminal is a paging failure and the terminal enters a connected state, sending the stored downlink data to the terminal, the first access network device being the access network device that last served the terminal.

[0042] In some possible implementations, storing the downlink data based on the third indication information includes: storing the downlink data based on the third indication information when the paging result of the first access network device paging the terminal is a paging failure, and the first access network device is the access network device that last served the terminal.

[0043] In some possible implementations, the downlink data is voice service data.

[0044] In some possible implementations, receiving the second subscription request includes: receiving the second subscription request in a session establishment process or a session modification process of the terminal.

[0045] In a fifth aspect, the present application provides a communication method, applied to a first network element or a second network element, the method comprising: sending a second subscription request, the second subscription request being used to request notification of receipt of downlink data sent to a terminal, the terminal being in an inactive state of radio resource control RRC; receiving a third notification message, the third notification message being used to indicate receipt of downlink data sent to the terminal; and sending third indication information in response to the third notification message, the third indication information being used to store the downlink data of the terminal.

[0046] Using the communication method provided in an embodiment of the present application, the second network element sends a second subscription request to the third network element based on the terminal being in an RRC inactive state, and in response to receiving a third notification message from the third network element, the second network element sends the third indication information to the third network element, causing the third network element to store the received downlink data. Thus, in a scenario where the first access network device's paging result for the terminal fails, and the terminal switches from an RRC inactive state to an idle state and ultimately enters a connected state, the third network element can immediately send the stored downlink data to the terminal without waiting for retransmission of the downlink data, thereby reducing service latency.

[0047] In some possible implementations, sending the second subscription message includes: sending the second subscription request based on the terminal being in an RRC inactive state.

[0048] In some possible implementations, the sending of the third indication information includes: when a paging result of the first access network device paging the terminal is a paging failure, sending the third indication information in response to the third notification message.

[0049] In some possible implementations, the downlink data is voice service data.

[0050] In a sixth aspect, the present application provides a communication system, the system comprising a first network element, a second network element, and a third network element, the third network element being used to implement the method described in any possible implementation of the first aspect or the fourth aspect, the second network element being used to implement the method described in any possible implementation of the second aspect, the third aspect or the fifth aspect, and the first network element being used to implement the method described in any possible implementation of the third aspect or the fifth aspect.

[0051] In a seventh aspect, the present application provides a communication device, comprising a processor configured to read and execute a computer program stored in a memory to implement the method described in any of the implementations of the corresponding aspects of the embodiments of the present application. In some possible implementations, the communication device further comprises the aforementioned memory. Optionally, the processor and memory are integrated.

[0052] In a possible implementation, the processor is configured to support the device in executing corresponding functions in the communication method, and the memory is used to store computer programs (or computer executable instructions) and / or data necessary for the device.

[0053] In some possible implementations, the apparatus further includes a communication interface configured to support communication between the apparatus and other network elements, such as the transmission or reception of data and / or signals. Exemplarily, the communication interface may be a transceiver, circuit, bus, module, or other type of communication interface.

[0054] In some possible implementations, the device is a chip.

[0055] In an eighth aspect, an embodiment of the present application provides a computer program product comprising instructions, which, when run on an electronic device, enables the electronic device to execute the method shown in any implementation method in the corresponding aspect of the embodiment of the application.

[0056] In a ninth aspect, the present application provides a computer-readable storage medium for storing a computer program. When the computer program is executed, the method shown in any implementation method in the corresponding aspect of the embodiment of the present application is implemented.

[0057] In a tenth aspect, the present application provides a chip module, comprising a transceiver component and a chip, wherein the chip is used to execute the method shown in any implementation method in the corresponding aspect of the embodiment of the present application.

[0058] It is understandable that the communication device, communication system, computer storage medium, computer program, computer program product, and chip system provided above are all used to execute the method shown in any implementation of the corresponding aspects of the embodiments of the present application. Therefore, the beneficial effects that can be achieved can refer to the beneficial effects of the corresponding methods and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] FIG1 is a schematic diagram of the architecture of a communication system used in an embodiment of the present application;

[0060] FIG2 is a flow diagram illustrating a situation in which the last gNB is unable to page the UE based on RAN paging in another communication solution provided by an embodiment of the present application, and the UE needs to re-access the network based on core network paging;

[0061] FIG3 is a schematic diagram of an interaction flow of a communication method provided in an embodiment of the present application;

[0062] FIG4 is a schematic diagram of a timeline of a solution provided in an embodiment of the present application that can reduce service latency in a corresponding scenario;

[0063] FIG5 is a schematic diagram of a timeline for reducing service latency in a corresponding scenario using another solution provided by an embodiment of the present application;

[0064] FIG6 is a schematic diagram of an interaction flow of another communication method provided in an embodiment of the present application;

[0065] FIG7 is a schematic diagram of an interaction flow of a possible implementation of the communication method shown in FIG3 provided in an embodiment of the present application;

[0066] FIG8 is a schematic diagram of an interaction flow of another possible implementation of the communication method shown in FIG3 provided in an embodiment of the present application;

[0067] FIG9 is a schematic diagram of an interaction flow of a possible implementation of the communication method shown in FIG6 provided in an embodiment of the present application;

[0068] FIG10 is a schematic diagram of an interaction flow of another possible implementation of the communication method shown in FIG6 provided in an embodiment of the present application;

[0069] FIG11 is a schematic diagram of an interaction flow of another communication method provided in an embodiment of the present application;

[0070] FIG12 is a schematic structural diagram of a communication device provided in an embodiment of the present application;

[0071] FIG13 is a schematic structural diagram of another communication device provided in an embodiment of the present application;

[0072] FIG14 is a schematic structural diagram of another communication device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0073] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0074] The solution provided in this application can be applied to a variety of communication systems. For example, the communication system can be a fifth-generation (5G) communication system or a non-terrestrial network (NTN), or it can also be a fourth-generation (4G) communication system (such as a long-term evolution (LTE) system), a 5G communication system, a fusion system of multiple systems such as NTN, or a future communication system, such as a 6G communication system. Among them, the 5G communication system can also be called a new radio (NR) system.

[0075] Figure 1 is a schematic diagram of a communication system architecture according to an embodiment of the present application, which uses the 5G network architecture based on a service-oriented architecture in a non-roaming scenario defined in the 3rd Generation Partnership Project (3GPP) standardization process as an example. The network architecture can include three parts: the terminal part, the 5G system, and the data network (DN).

[0076] The terminal portion may include a terminal 110, which may also be referred to as user equipment (UE). The terminal 110 in this application is a device with wireless transceiver capabilities that can communicate with one or more core network (CN) devices (or core devices) via access network equipment (or access devices) in the RAN 140. The terminal 110 may also be referred to as an access terminal, terminal, subscriber unit, subscriber station, mobile station, mobile station, remote station, remote terminal, mobile device, user terminal, user agent, or user device. The terminal 110 may be deployed on land, including indoors or outdoors, handheld or vehicle-mounted; on water (such as a ship); or in the air (such as an airplane, balloon, or satellite). The terminal 110 may be a cellular phone, a cordless phone, a Session Initiation Protocol (SIP) phone, a smart phone, a mobile phone, a wireless local loop (WLL) station, a personal digital assistant (PDA), or the like. Alternatively, the terminal 110 may be a handheld device with wireless communication capabilities, a computing device, or other device connected to a wireless modem, an in-vehicle device, a wearable device, an unmanned aerial vehicle device, or a terminal in the Internet of Things or the Internet of Vehicles, a terminal of any form in a 5G network or future network, a relay user device, or a terminal in a future evolved 5G system, etc. Among them, the relay user device may be, for example, a 5G residential gateway (RG). For example, the terminal 110 may be a virtual reality (VR) terminal, an augmented reality (AR) terminal, a wireless terminal in industrial control, a wireless terminal in self-driving, a wireless terminal in remote medical care, a wireless terminal in a smart grid, a wireless terminal in transportation safety, a wireless terminal in a smart city, a wireless terminal in a smart home, etc. The embodiments of the present application do not limit the type or category of the terminal.

[0077] Data network DN 120, also known as a packet data network (PDN), is typically a network located outside the 5G system, such as a third-party network. For example, the 5G system can access multiple data networks DN 120, and multiple services can be deployed on the data network DN 120 to provide data and / or voice services to the terminal 110. For example, data network DN 120 can be the private network of a smart factory, and the sensors installed in the workshop of the smart factory can be terminals 110. The data network DN 120 has a control server for the sensors deployed, and the control server can provide services for the sensors. The sensors can communicate with the control server, obtain instructions from the control server, and transmit the collected sensor data to the control server according to the instructions. For another example, data network DN 120 can be the internal office network of a company, and the mobile phones or computers of the company's employees can be terminals 110. The employees' mobile phones or computers can access information, data resources, etc. on the company's internal office network. The terminal 110 can establish a connection with the 5G system through an interface provided by the 5G system (such as the N1 interface in Figure 1) and use data and / or voice services provided by the 5G system. The terminal 110 can also access the data network DN 120 through the 5G system, use the operator services deployed on the data network DN 120, and / or services provided by a third party. The third party may be a service provider other than the 5G system and the terminal 110, and may provide other data and / or voice services to the terminal 110. The specific form of the third party can be determined according to the actual application scenario and is not limited here.

[0078] The core network may include: network exposure function (NEF) 131, network function repository function (NRF) 132, policy control function (PCF) 133, unified data management (UDM) 134, application function (AF) 135, authentication server function (AUSF) 136, access and mobility management function (AMF) 137, session management function (SMF) 138, user plane function (UPF) 139, and RAN 140. In the above 5G system, the part other than the (radio) access network 140 can be referred to as the core network part or core network part.

[0079] For example, the following briefly introduces the network functions in the 5G system.

[0080] RAN 140 is a subnetwork of the 5G system and serves as the implementation system between service nodes (or network functions) in the 5G system and terminal 110. To access the 5G system, terminal 110 first passes through RAN 140 and then connects to a service node in the 5G system through RAN 140. The access network device in the embodiments of the present application is a device that provides wireless communication functions for terminal 110 and may also be referred to as an access device, RAN device, or network device. For example, the access device includes but is not limited to: the next generation node basestation (gNB) in the 5G system, the evolved node B (eNB) in the LTE system, the radio network controller (RNC), the node B (NB), the base station controller (BSC), the base transceiver station (BTS), the home evolved nodeB (or home node B, HNB), the base band unit (BBU), the transmission and receiving point (TRP), the transmitting point (TP), the small base station equipment (pico), the mobile switching center, or the network equipment in the future network, etc. It is understandable that the present application does not limit the specific type of access network equipment. In systems using different wireless access technologies, the names of devices with access network equipment functions may be different.

[0081] Optionally, in some deployments of access devices, the access device may include a centralized unit (CU) and a distributed unit (DU). In other deployments of access devices, the CU may be further divided into a CU-control plane (CP) and a CU-user plane (UP). In still other deployments of access devices, the access device may also be an open radio access network (ORAN) architecture. This application does not limit the specific deployment method of the access device.

[0082] The network open function NEF (also known as NEF network function or NEF network function entity) 131 is a control plane function provided by the operator. NEF131 opens the external interface of the 5G system to third parties in a secure manner. When SMF 138 needs to communicate with the network function of a third party, NEF131 can serve as a relay for communication between SMF 138 and the network entity of the third party. When NEF131 acts as a relay, it can translate the identification information of the subscriber and the identification information of the network function of the third party. For example, when NEF131 sends the subscriber's subscriber permanent identifier (SUPI) from the 5G system to a third party, it can translate the SUPI into its corresponding external identity (ID). Conversely, when NEF131 sends an external ID (network entity ID of a third party) to the 5G system, it can translate it into SUPI.

[0083] The network storage function NRF 132 can be used to maintain real-time information of all network function services in the network.

[0084] The policy control function PCF 133 is a control plane function provided by the operator, and is used to provide protocol data unit (PDU) session policies to the SMF 138. Policies may include charging-related policies, QoS-related policies, and authorization-related policies.

[0085] Unified Data Management UDM 134 is a control plane function provided by the operator, which is responsible for storing information such as the subscriber permanent identifier (SUPI), security context, and subscription data of the subscribers in the 5G system. The subscribers of the above-mentioned 5G system may specifically be users who use the services provided by the 5G system, such as users who use the terminal chip cards of China Telecom, or users who use the terminal chip cards of China Mobile, etc. Exemplarily, the SUPI of the subscriber may be the number of the terminal chip card, etc. The above-mentioned security context may be data (cookie) or token stored on the local terminal (such as a mobile phone). The subscription data of the above-mentioned subscriber may be the supporting services of the terminal chip card, such as the traffic package of the mobile phone chip card, etc.

[0086] The application function AF 135 is used to perform data routing affected by the application, access network open functions, interact with the policy framework for policy control, etc.

[0087] The authentication server function AUSF 136 is a control plane function provided by the operator, and is usually used for level one authentication, i.e. authentication between the terminal 110 (subscriber) and the 5G system.

[0088] AMF 137 is a control plane network function provided by the 5G system, responsible for access control and mobility management of the terminal 110 accessing the 5G system, such as mobility state management, allocation of user temporary identity, authentication and authorization of users, etc.

[0089] SMF 138 is a control plane network function provided by the 5G system, responsible for managing the protocol data unit (PDU) session of the terminal 110. A PDU session is a channel for transmitting PDUs, and the terminal needs to transmit PDUs to and from the DN 120 through a PDU session. The PDU session can be established, maintained, and deleted by the SMF 138. SMF 138 includes session management (such as session establishment, modification, and release, including tunnel maintenance between the UPF 139 and the RAN 140), selection and control of the UPF 139, service and session continuity (SSC) mode selection, roaming, and other session-related functions.

[0090] The UPF 139 is a gateway provided by the operator and serves as the gateway for communication between the 5G system and the DN 120. The UPF 139 includes user-plane-related functions such as packet routing and transmission, packet inspection, service usage reporting, Quality of Service (QoS) processing, uplink packet inspection, and downlink packet storage.

[0091] The network functions in the 5G system shown in FIG1 may further include a network slice selection function (NSSF) (not shown in FIG1 ), which is responsible for determining a network slice instance, selecting an AMF 137, etc. The network functions in the 5G system shown in FIG1 may further include a unified data repository (UDR), etc. The embodiments of the present application do not limit other network functions included in the 5G system.

[0092] In Figure 1, Nnef, Nausf, Nnrf, Npcf, Nudm, Naf, Namf, Nsmf, N1, N2, N3, N4, and N6 are interface serial numbers. For example, the meanings of the above interface serial numbers can be found in the meanings defined in the 3GPP standard protocol, and this application does not limit the meanings of the above interface serial numbers. It should be noted that Figure 1 only uses terminal 110 as a UE for exemplary illustration, and the interface names between the various network functions in Figure 1 are only examples. In specific implementations, the interface names of the system architecture may also be other names, and this application does not limit this.

[0093] In an embodiment of the present application, the first network element that executes the communication solution provided by the present application may be the AMF 137 shown in FIG1 , or may be another network element in a future communication system that has the network function of the AMF 137. The second network element that executes the communication solution provided by the present application may be the SMF 138 shown in FIG1 , or may be another network element in a future communication system that has the network function of the SMF 138. The third network element that executes the communication solution provided by the present application may be the UPF 139 shown in FIG1 , or may be another network element in a future communication system that has the network function of the UPF 139. Alternatively, the access and mobility management function network element in the present application may also be a mobility management entity (MME) in an LTE system, etc.

[0094] For ease of explanation, in the embodiment of the present application, the user plane function network element UPF 139 is referred to as UPF, the session management function network element SMF 138 is referred to as SMF, and the access and mobility management function network element AMF 137 is referred to as AMF. That is, the AMF described later in the embodiment of the present application can be replaced with the access and mobility management function network element. It is understood that other network functions not shown are also applicable to this replacement method.

[0095] The network architecture shown in Figure 1 (e.g., 5G network architecture) adopts a service-based architecture and universal interfaces. Traditional network element functions are split into several self-contained, self-managed, and reusable network function service modules based on network function virtualization (NFV) technology. The network architecture diagram shown in Figure 1 can be understood as a service-based 5G network architecture diagram in a non-roaming scenario. In this architecture, different network functions are combined in an orderly manner according to specific scenario requirements, which can achieve customization of network capabilities and services, thereby avoiding the deployment of dedicated physical networks for different services. Network slicing technology enables operators to respond to customer needs more flexibly and quickly, and supports the flexible allocation of network resources.

[0096] The following introduces some communication terms involved in this application.

[0097] (1) The network status of the terminal.

[0098] In 5G communication systems, the connection management state (CM state) is used to identify whether a connection between a terminal and the core network exists. The CM state includes the CM connected state and the CM idle state. In the CM connected state, the radio resource control (RRC) state has two states: the RRC connected state and the RRC inactive state. In the CM idle state, the RRC state of the terminal is idle.

[0099] When a terminal is in the RRC inactive state, the connection between the terminal and the RAN is disconnected, but the communication connection established between the RAN and the core network for the terminal remains. When the terminal is in the RRC connected state, the connection between the terminal and the RAN is established, and the RAN and the core network also have a communication connection established for the terminal. When the terminal is in the RRC idle state, the connection between the terminal and the RAN is disconnected, and the connection established between the RAN and the core network for the terminal is also disconnected.

[0100] The full name of the RRC inactive state is CM connected with RRC inactive state, which means that the terminal maintains the CM connected state when in the RRC inactive state. For ease of description, CM connected with RRC inactive state is referred to as RRC inactive state. It should be noted that while the terminal maintains the CM connected state when in the RRC inactive state, the term "terminal in connected state" or "terminal in CM connected state" described in this application means that both the CM state and the RRC state of the terminal are in the connected state.

[0101] Generally, unless the core network specifically subscribes to the RAN for the terminal's RRC state, the core network is unaware of the terminal's transition between the CM Connected state and the RRC Inactive state. Specifically, in the RRC Inactive state, the RRC connection between the terminal and the base station is released, but the connection between the base station and the core network for the terminal remains, and the base station retains the terminal's context. This allows the terminal to quickly reconnect to the network the next time. When the terminal is in the RRC Inactive state, low-latency control requirements can be achieved with minimal signaling, while maintaining power consumption close to that of the terminal in the LTE CM Idle state. This also maximizes the number of terminals that can be served with the same resource consumption within the RAN / CN.

[0102] (2)RAN paging and core network paging.

[0103] RAN paging refers to the process where, when a terminal is in the RRC Inactive state and downlink data needs to be sent to it, the base station that last served the terminal (the last gNB), as well as other base stations within the terminal's RAN notification area that have an Xn connection to the last gNB, notify the terminal of the access network via a RAN Paging message, causing the terminal to switch from the RRC Inactive state to the CM Connected state to initiate data transmission. It should be noted that the base station (or access network device) that last served the terminal described in this application refers to the base station that last served the terminal as perceived by the UPF (or the core network), not the base station that last served the terminal as perceived by the terminal.

[0104] Core network paging refers to the process whereby when a terminal is in CM Idle state and has downlink data to send, the core network paging the terminal via a paging message, switching the terminal from CM Idle state to CM Connected state to initiate data transmission. It should be noted that core network paging ultimately involves the base station sending a paging message to the terminal, but the paging range of the core network paging is larger than the paging range of the RAN notification area to which the terminal belongs. In 5G communication systems, core network paging is also called 5GC paging.

[0105] Generally, when a terminal is in the RRC Inactive state, if the AF sends downlink data for the terminal to the UPF, the core network sends the downlink data request to the last gNB, which then pages the terminal via RAN paging within the terminal's RAN notification area. The last gNB pages the terminal not only from its own base station but also through other external cells that have an Xn interface with the last gNB and are part of the RNA. However, if the base station currently covering the terminal (the new gNB) is not the same as the last gNB, and the Xn interface between the last gNB and the new gNB fails, RNA paging will fail to successfully page the terminal. In this case, after determining that the terminal is unreachable, the last gNB triggers the user plane resource release procedure (AN release procedure), causing the terminal to transition from the RRC Inactive state to the CM Idle state. After the terminal transitions to the CM Idle state, it is paged again via core network paging, which has a wider paging range than RAN paging. The terminal ultimately reconnects to the network by executing a service request procedure.

[0106] However, in actual applications, it is found that after the terminal reconnects to the network from the RRC inactive state through core network paging, that is, enters the CM connection state, the terminal still needs to wait for a long time to receive the downlink data from the new gNodeB, resulting in serious service delay problems.

[0107] Further analysis reveals that in some other communication methods, as shown in Figure 2, after the UPF receives downlink data from the AF (e.g., an invite request from the P-CSCF), it sends the invite request to the last gNB. In response to the invite request, the last gNB pages the terminal using RAN paging. However, in step S201, the last gNB sends an Xn Paging message to the new gNB, instructing the new gNB to send a RAN Paging message to the terminal. However, the last gNB may be unable to communicate with the new gNB, for example, due to a fault in the Xn interface between the last gNB and the new gNB, resulting in Xn Paging failure, meaning that the terminal cannot be successfully paged via RAN paging. In this case, after the paging process times out and the last gNB determines that the terminal is unreachable, it discards the invite message (S202), triggering step S203: the last gNB triggers the user plane resource release procedure (AN release procedure), transitioning the terminal to the CM Idle state. After the terminal transitions to the CM Idle state, as shown in steps S204-S205, it waits for the core network to trigger a 5GC paging call (shown in Figure 2 as the AMF initiating a 5GC paging call to the terminal via the new gNB). The terminal then executes a service request to connect to the network, entering the CM Connected state. As shown in step S206, after the terminal enters the CM Connected state, the UPF waits for a retransmitted invite request from the P-CSCF and then sends the invite request to the terminal in the Connected state.

[0108] This means that when a terminal reconnects to the network, the last gNB will discard the downlink data due to a timeout. After reconnecting to the network, the terminal must wait for the source of the downlink data to retransmit. Current communication standards do not align the downlink data retransmission timeout period with the time it takes for the terminal to transition from RRC Inactive to RRC Idle and then back to Connected. This means that after reconnecting to the network, the terminal must wait for downlink data retransmission before successfully receiving it. This can lead to significant service latency issues, significant inconvenience for the calling user, and a poor user experience.

[0109] As an example, the timeout retransmission duration can be up to 32 seconds (s), and the time it takes for the terminal to migrate from the RRC inactive state to the CM idle state and then enter the CM connected state is, for example, 6s. After the terminal enters the CM connected state, it needs to wait at least 26s to successfully receive the downlink data packet, and the delay problem is prominent.

[0110] As another example, the time it takes for the terminal to migrate from the RRC inactive state to the CM idle state and then to the CM connected state is about 6 seconds, and the timeout retransmission duration is linked to the number of timeouts, where the later the number of timeouts, the longer the timeout retransmission duration. For example, the first timeout retransmission duration is 5 seconds, and the second timeout retransmission duration is 10 seconds. When the UPF receives the first retransmitted downlink data (at the 5th second), the terminal has not yet entered the CM connected state. When the UPF receives the first retransmitted downlink data (at the 15th second), it is already the 9th second since the terminal entered the CM connected state. In other words, the terminal must wait for at least 9 seconds to successfully receive the downlink data packet, and the delay problem is prominent.

[0111] In view of this, the present application provides a communication solution to reduce the service delay in the scenario where the terminal is in an RRC inactive state and the last gNB cannot reach the terminal.

[0112] It should be noted that in this embodiment of the present application, the description of the base station that last served the terminal as the last gNB and the description of the base station that currently covers the terminal as the new gNB are merely examples. Other appropriate names are also possible and are not limited in this document. For example, in other descriptions, the last gNB may also be referred to as the old gNB, the last serving gNB, or the source gNB, and the new gNB may also be referred to as the new serving gNB or the target gNB. The term gNB may also be replaced by NG-RAN, RAN, or other descriptions, which are not limited in this document.

[0113] The following is a flow chart of the communication method provided by this application, described in conjunction with FIG3. As shown in FIG3, the communication method includes:

[0114] S301, a second network element sends a first subscription request to a first network element, where the first subscription request is used to request notification of a terminal entering an RRC inactive state; accordingly, the first network element receives the first subscription request.

[0115] In an embodiment of the present application, the second network element sends a first subscription request to the first network element, and the subscription terminal enters the RRC inactive state, which means that the second network element requests the first network element to send a relevant subscription notification to the second network element when the terminal enters the RRC inactive state.

[0116] As an example, the second network element may send the first subscription request to the first network element during the PDU session establishment process of the terminal. It should be noted that, before the PDU session establishment process of the terminal, if the second network element has already sent the first subscription request to the first network element, the second network element may not send the first subscription request again.

[0117] As an example, the second network element can subscribe the terminal to the RRC inactive state to the first network element through a service message, such as Namf_EventExposure_Subscribe or Nsmf_PDUSession_SMContextStatusNotify.

[0118] In an embodiment of the present application, a first subscription request may correspond to one or more terminals, that is, the first subscription request may be used to subscribe to information that one or more terminals enter an RRC inactive state, which is not limited in this document.

[0119] As an example, the first subscription request may include a UE identifier of the terminal, or one or more session identifiers corresponding to the terminal, to indicate the terminal to which the RRC state needs to be subscribed.

[0120] It should be noted that the session identifier carried in the interactive signaling between the second network element and the first network element can be the PDU session ID corresponding to the PDU session or can be a private identifier for identifying the session between the second network element and the first network element, for example, the private identifier can be an SM context ID. The PDU session ID can be understood as the public identifier of the session, and the SM context ID is a private identifier allocated by the second network element to the session and used to identify the session between the second network element and the first network element.

[0121] S302: The first network element determines that the terminal enters an RRC inactive state.

[0122] As an example, the first network element can obtain the RRC status of the terminal from the base station serving the terminal to determine whether the terminal enters the RRC inactive state, thereby providing a subscription notification service for the first subscription request of the second network element based on the RRC status of the terminal.

[0123] S303, after determining that the terminal enters the RRC inactive state, the first network element sends a first notification message to the second network element based on the first subscription request, where the first notification message is used to notify the terminal to enter the RRC inactive state; accordingly, the second network element receives the first notification message.

[0124] As an example, the first network element may send the above-mentioned first notification message to the second network element through a service message, such as Namf_EventExposure_Notify or Nsmf_PDUSession_SMContextStatusNotify, to notify the second network element that the terminal enters the RRC inactive state.

[0125] As an example, the first notification message may include the UE identifier of the terminal, or the first notification message may include one or more session identifiers of the terminal. If the first notification message includes one or more session identifiers, the first notification message is used to indicate that the RRC state of the terminal corresponding to the one or more session identifiers enters the RRC inactive state.

[0126] S304, in response to the terminal entering the RRC inactive state, the second network element sends first indication information to the third network element, where the first indication information is used to store downlink data sent to the terminal; accordingly, the third network element receives the first indication information.

[0127] As an example, the second network element may send the first indication information to the third network element during a session establishment process or a session modification process of the terminal. For example, in response to a data request from a calling user of the terminal, a corresponding session is established between the second network element and the third network element for the terminal, and during the session establishment process, the second network element receives a subscription notification indicating that the terminal has entered an RRC inactive state. In this case, the second network element may send the first indication information to the third network element based on the session establishment process.

[0128] For example, a terminal-related session modification process is performed between the second network element and the third network element, and during the session modification process, the second network element receives a subscription notification that the terminal enters the RRC inactive state. The second network element can send the above-mentioned first indication information to the third network element based on the session modification process.

[0129] As an example, the first indication information may include the UE identifier of the terminal, or the first indication information may also include one or more session identifiers of the terminal to indicate the terminal of the downlink data to be stored. If the first indication information includes the UE identifier of the terminal, the first indication information is UE granularity, which is used to indicate the storage of all downlink data sent to the terminal. If the first indication information includes the one or more session identifiers, the first indication information is session granularity, which is used to indicate the storage of downlink data of the corresponding session.

[0130] It should be noted that the session identifier carried in the interactive signaling between the second network element and the third network element can be a PDU session ID or other private identifiers (for example, N4session ID), where the N4session ID is a private identifier that identifies one or more sessions of the same terminal between the second network element and the third network element.

[0131] In some other possible implementations, the second network element sends a first subscription request to the first network element, and the second network element sends the above-mentioned first indication information to the third network element based on the first notification message. It can also be understood that: the second network element obtains the RRC status of the terminal from the first network element, and sends the first indication information to the third network element when the second network element determines that the RRC state of the terminal is an RRC inactive state.

[0132] In some other possible implementations, the second network element sends a first subscription request to the first network element, and the second network element sends a first indication message to the third network element based on the terminal entering the RRC inactive state. It can also be understood that: the second network element obtains the RRC state of the terminal from the first network element, and sends the first indication message to the third network element when the second network element determines that the RRC state of the terminal is the RRC inactive state.

[0133] In some other possible implementations, the first network element may directly send the first indication information to the third network element via the second network element based on the terminal entering the RRC inactive state, or based on the terminal being in the RRC inactive state and the paging result of the first access network device paging the terminal being a paging failure. In this manner, the second network element does not need to subscribe to the first network element for the terminal to enter the RRC inactive state; the second network element only needs to forward the first indication information sent by the first network element to the third network element.

[0134] It should be noted that the first access network device paging the terminal described in this article refers to the first access network device paging the terminal based on the RAN manner, rather than only the first access network device paging the terminal.

[0135] S305: The third network element receives downlink data sent to the terminal.

[0136] In the embodiment of the present application, the destination end of the downlink data is the terminal, that is, the downlink data is downlink data that needs to be sent to the terminal.

[0137] As an example, the downlink data may come from a third-party application, such as voice service data, and the third-party application may be a P-CSCF. For example, when a voice called service needs to be initiated, the P-CSCF sends an invite request (downlink data) to the third network element.

[0138] S306: The third network element stores the downlink data based on the first indication information.

[0139] In the embodiment of the present application, the indication method of the first indication information can be an explicit or implicit indication method.

[0140] In the explicit indication mode, the first indication information instructs the third network element to store downlink data sent to the terminal. For example, the first indication information may be indication information agreed upon between the second network element and the third network element to instruct the storage of downlink data of the terminal, such as a string or a Boolean value. In this case, the third network element may not be aware that the terminal has entered the RRC inactive state.

[0141] In the implicit indication mode, the first indication information is not directly used to instruct the third network element to store the downlink data sent to the terminal. For example, the second network element notifies the third network element that the terminal is in the RRC inactive state (that is, the first indication information indicates that the terminal is in the RRC inactive state), and the third network element actively stores the downlink data sent to the terminal based on the terminal being in the RRC inactive state (rather than the second network element directly instructing the third network element to store the downlink data sent to the terminal). It can also be understood that the third network element subscribes to the second network element or the first network element that the terminal enters the RRC inactive state, the first indication information is a subscription notification that the terminal enters the RRC inactive state, and the third network element stores the downlink data sent to the terminal based on the terminal entering the RRC inactive state. In this case, the third network element can sense that the terminal has entered the RRC inactive state.

[0142] S307 , after the terminal enters the CM connection state, the third network element sends the stored downlink data to the terminal; correspondingly, the terminal receives the downlink data.

[0143] In an embodiment of the present application, in a scenario where the terminal is in an RRC inactive state and the paging result of the first access network device paging the terminal is a paging failure, after the terminal migrates from the RRC inactive state to the CM idle state and finally enters the CM connected state, the third network element sends the above-mentioned stored downlink data to the terminal without waiting for the retransmission of the downlink data before sending the downlink data to the terminal, thereby reducing the service delay in this scenario.

[0144] As an example, the third network element may send the stored downlink data to the terminal after sensing that the terminal has entered a CM connected state, in which the RRC state of the terminal is also a connected state. As another example, the third network element may send the stored downlink data to the terminal after sensing that the terminal has entered an RRC connected state.

[0145] As an example, a first list is stored in a third network element, and the first list is used to record the association relationship between the downlink data to be sent and the session identifier corresponding to the downlink data. When the third network element determines that the session identifier corresponding to the currently established user plane resource is included in the first list, indicating that the terminal corresponding to the session identifier enters the RRC connection state and the CM connection state, the third network element determines the corresponding downlink data from the first list based on the session identifier, and sends the downlink data to the corresponding terminal based on the user plane resource.

[0146] In some possible implementations, after storing the downlink data sent to the terminal in step S306, the third network element may further set a timer and delete the downlink data after the timer expires. As an example, the duration of the timer may be related to the timeout retransmission duration of the downlink data and / or a second duration, where the second duration is the maximum duration consumed by the terminal switching from the RRC inactive state to the CM idle state and then entering the CM connected state. It should be noted that this method is applicable not only to the communication method shown in Figure 3 but also to other embodiments of this document, and is not limited to this herein.

[0147] In some possible implementations, the first subscription request is further used to request notification of the terminal entering a CM-connected state. After the terminal enters the CM-connected state, the first network element sends a second notification message to the second network element based on the first subscription request, where the second notification message is used to instruct the terminal to enter a connected state. Based on the terminal entering the CM-connected state, the second network element sends second indication information to a third network element, where the second indication information is used to instruct the third network element to delete the downlink data after sending the downlink data to the terminal and / or to instruct the third network element to no longer store the downlink data sent to the terminal.

[0148] Using the communication method provided in an embodiment of the present application, a third network element stores downlink data sent to a terminal based on the first indication information. That is, after the terminal enters the RRC inactive state, the third network element stores the downlink data sent to the terminal. In this way, in a scenario where the first access network device fails to page a terminal in the RRC inactive state and the first access network device discards the downlink data, after the terminal enters the CM connected state based on the core network paging method, the third network element can immediately send the stored downlink data to the terminal without waiting for the source of the downlink data to resend the downlink data to the third network element, thereby reducing service latency in this scenario.

[0149] As an example, assuming that the second duration of the terminal migrating from the RRC inactive state to the CM idle state and then entering the CM connected state is 6s, the timeout retransmission duration of the downlink data can be up to 32s. Please refer to the timeline shown in Figure 4, and record the moment when the third network element receives the downlink data sent to the terminal as 0s. Before 0s, the terminal enters the RRC inactive state and the third network element receives the above-mentioned first indication information. After receiving the downlink data at 0s, the third network element stores the downlink data based on the first indication information. At 6s, the terminal enters the CM connected state, and the third network element sends the stored downlink data to the terminal at the first time. There is no need for the terminal to enter the CM connected state and wait for 26s (that is, 32s) before the source end of the downlink data resends the downlink data to the third network element. The third network element can successfully send the downlink data to the terminal, thereby reducing service latency.

[0150] In some other possible implementations, the above-mentioned step S304 includes: when the terminal is in an RRC inactive state and the paging result of the first access network device paging the terminal is a paging failure, the second network element sends a first indication information to the third network element, and the first access network device is the access network device that last served the terminal.

[0151] In this manner, the second network element can determine that the terminal is in an RRC inactive state based on the above-mentioned first notification message, and determine that the paging result of the first access network device paging the terminal is a paging failure based on the request received from the first network element for requesting the release of the user plane resources of the terminal (for example, the Nsmf_PDUSession_UpdateSMContext message), and then determine to send the first indication information to the third network element.

[0152] In this manner, as an example, the first indication information instructs the third network element to store downlink data sent to the terminal. As another example, the first indication information indicates that the terminal is in an RRC inactive state.

[0153] As another example, the first indication information can also be used to indicate that the terminal is in an RRC inactive state and the paging result of the first access network device paging the terminal is a paging failure, and the first access network device is the access network device that last served the terminal. For example, the first indication information carries the reason information that the terminal is in an RRC inactive state and the paging result of the first access network device paging the terminal is a paging failure, or the N4 modification request message sent by the second network element to the third network element to request the release of the user plane resources of the terminal also carries the reason information that the terminal is in an RRC inactive state and the paging result of the first access network device paging the terminal is a paging failure (that is, it also carries the first indication information).

[0154] Understandably, considering that when a terminal is in an RRC inactive state, if the first access network device can page the terminal (i.e., the terminal can directly enter a CM connected state from an RRC inactive state), then the third network element may not need to store the terminal's downlink data. However, if the third network element still needs to store the downlink data in this scenario, then the third network element can directly send the downlink data to the terminal via the first access network device before storing the data. The stored downlink data will not be used later, and the utilization rate of the stored data needs to be improved.

[0155] Therefore, using this method, the second network element sends the first indication information to the third network element only when it determines that the terminal is in the RRC inactive state and determines that the paging result of the terminal paging based on the first access network device is a paging failure, so that the third network element stores the downlink data of the terminal. On the one hand, after the terminal enters the CM connected state, if the third network element has stored the downlink data, the third network element can directly send the stored downlink data to the terminal, thereby reducing the probability that the third network element needs to wait for the retransmission of the downlink data before sending the downlink data to the terminal after the terminal enters the CM connected state, thereby reducing service latency. On the other hand, it can reduce the problem of ineffective storage of the downlink data stored by the third network element that will not be used when the terminal is in the RRC inactive state and the terminal can be paged based on the first access network device, further improve the utilization rate of the stored downlink data, reduce unnecessary storage overhead, and alleviate the data storage pressure of the third network element.

[0156] As an example, assume that the second duration for a terminal to transition from the RRC Inactive state to the CM Idle state and then to the CM Connected state is 6 seconds, of which the duration of the terminal transitioning from the RRC Inactive state to the CM Idle state is 3 seconds, the first timeout retransmission duration for downlink data is 5 seconds, and the second timeout retransmission duration is 10 seconds. Referring to the timeline shown in FIG5 , the moment when the third network element receives the downlink data sent to the terminal is recorded as second 0. Before second 0, the terminal enters the RRC Inactive state. At second 3, the second network element determines that the paging result for the terminal is a paging failure and sends a first indication message to the third network element. At second 5, the downlink data is retransmitted for the first time. At second 6, the terminal enters the CM Connected state. The third network element immediately sends the stored downlink data to the terminal without waiting for another 9 seconds (i.e., at second 15). The downlink data can only be sent to the terminal after the third network element receives the second timeout retransmission of the downlink data, thereby reducing service latency.

[0157] In some other possible implementations, step S306 may include: when the terminal is in an RRC inactive state and the paging result of the first access network device paging the terminal is a paging failure, the third network element stores the above-mentioned downlink data sent to the terminal based on the first indication information, and the first access network device is the access network device that served the terminal for the last time.

[0158] In this manner, as an example, the first indication information is used to indicate that the terminal is in an RRC inactive state, and the third network element may determine that the terminal is in an RRC inactive state based on the first indication information, and the third network element determines that the paging result of the first access network device paging the terminal is a paging failure based on the N4 modification request message received from the second network element for requesting the release of user plane resources of the terminal. As another example, the first indication information is used to indicate that the terminal is in an RRC inactive state and the paging result of the first access network device paging the terminal is a paging failure, and the third network element may determine that the terminal is in an RRC inactive state and the paging result of the first access network device paging the terminal is a paging failure based on the first indication information.

[0159] Using this method, the third network element stores downlink data based on the first indication information only when it determines that the paging result of the paging terminal of the first access network device is a paging failure. While reducing service delay, it can further reduce unnecessary storage tasks for the downlink data, improve the utilization rate of the stored downlink data, and reduce unnecessary storage overhead.

[0160] In some other implementations provided in the embodiments of the present application, the first network element or the second network element may sense that the third network element has received downlink data sent to the terminal, and then the first network element or the second network element may instruct the third network element to store the downlink data based on the downlink data and the RRC state of the terminal. The communication method is described below in conjunction with Figure 6. As shown in Figure 6, the method includes:

[0161] S601: A second network element sends a second subscription request to a third network element, where the second subscription request is used to request notification of receipt of downlink data sent to a terminal; accordingly, the third network element receives the second subscription request.

[0162] As an example, when the terminal accesses the network for the first time, the second network element sends a second subscription request to the third network element.

[0163] As another example, the second network element sends a second subscription request to the third network element based on the terminal being in the RRC inactive state. The second network element can subscribe to the terminal entering the RRC inactive state by sending a first subscription request to the first network element. For an explanation of the first subscription request, reference can be made to the relevant explanation in the embodiment shown in FIG3 and will not be described in detail here.

[0164] As an example, the second network element may send a second subscription request to the third network element during the PDU session establishment process of the terminal.

[0165] S602: The third-party application sends downlink data to the third network element, where the downlink data is sent to the terminal. Correspondingly, the third network element receives the downlink data.

[0166] S603, the third network element sends a third notification message to the second network element in response to the second subscription request, where the third notification message is used to indicate that downlink data sent to the terminal has been received; accordingly, the second network element receives the third notification message.

[0167] It should be noted that the third notification message can be at the granularity of single data, session granularity, or UE granularity. That is, for the same downlink data (including the downlink data received for the first time and the retransmitted downlink data), the third network element can only send the third notification message to the second network element once. Alternatively, for different downlink data corresponding to the same session, the third network element can only send the third notification message to the second network element once. Alternatively, for downlink data corresponding to different sessions of the same terminal, the third network element can only send the third notification message to the second network element once.

[0168] S604, the second network element sends third indication information to the third network element in response to the third notification message, where the third indication information is used to store the downlink data; correspondingly, the third network element receives the third indication information.

[0169] In some possible implementations, after receiving the third notification message, the second network element sends the third indication information to the third network element.

[0170] In some other possible implementations, after receiving the third notification message and determining that the paging result of the first access network device paging the terminal is a paging failure, the second network element sends the third indication information to the third network element.

[0171] It should be noted that the third indication information can be at the granularity of a single data, a session, or a UE. That is, the third indication information can be used to store the downlink data, or to store all downlink data of the session corresponding to the downlink data, or to store all downlink data of all sessions of the terminal corresponding to the downlink data.

[0172] S605: The third network element stores the downlink data based on the third indication information.

[0173] In some possible implementations, after receiving the third indication information, the third network element stores the downlink data based on the third indication information.

[0174] In some other possible implementations, when the paging result of the first access network device paging the terminal is a paging failure, the third network element stores the downlink data based on the third indication information.

[0175] In the embodiment of the present application, the indication method of the third indication information can be an explicit or implicit indication method.

[0176] In the explicit indication mode, the third indication information instructs the third network element to store the downlink data sent to the terminal.

[0177] In the implicit indication mode, the third indication information is not directly used to instruct the third network element to store the downlink data sent to the terminal. As a physiological function, the second network element notifies the third network element that the terminal is in the RRC inactive state, that is, the third indication information indicates that the terminal is in the RRC inactive state, rather than the second network element directly instructing the third network element to store the downlink data sent to the terminal; the third network element stores the downlink data based on the terminal being in the RRC inactive state.

[0178] As another example of an implicit indication method, the third indication information may also be used to indicate that the terminal is in an RRC inactive state and the paging result of the first access network device's paging of the terminal is a paging failure, rather than the second network element directly instructing the third network element to store downlink data sent to the terminal, and the first access network device is the access network device that last served the terminal. The third network element stores the downlink data based on the fact that the terminal is in an RRC inactive state and the paging result of the first access network device's paging of the terminal is a paging failure.

[0179] In some possible implementations, the third indication information may have the same function and form as the first indication information in the description related to FIG. 3 , which is not limited herein.

[0180] S606 , after the terminal enters the CM connection state, the third network element sends the stored downlink data to the terminal; correspondingly, the terminal receives the downlink data.

[0181] Using the communication method provided in the embodiments of the present application, the second network element sends a second subscription request to the third network element based on the terminal being in the RRC inactive state, and in response to receiving the third notification message from the third network element, the second network element sends the third indication information to the third network element, so that the third network element stores the received downlink data. Thus, in a scenario where the paging result of the first access network device's paging of the terminal is a paging failure, and the terminal switches from the RRC inactive state to the CM Idle state and ultimately enters the CM Connected state, the third network element can send the stored downlink data to the terminal as soon as the terminal enters the CM Connected state, without having to wait for retransmission of the downlink data.

[0182] Alternatively, using the communication method provided in an embodiment of the present application, after receiving a third notification message from a third network element, the second network element, if it determines that the paging result of the first access network device to the terminal is a paging failure, further sends the third indication information to the third network element. Alternatively, after receiving the third notification message, the third network element, if it determines that the paging result of the first access network device to the terminal is a paging failure, further stores the downlink data. On one hand, after the terminal enters the CM connected state, if the third network element has stored the downlink data, the third network element can directly send the stored downlink data to the terminal, thereby reducing the probability that the third network element will need to wait for the downlink data to be retransmitted before sending the downlink data to the terminal after the terminal enters the CM connected state, thereby reducing service latency. On the other hand, this can reduce the problem of inefficient storage of downlink data stored by the third network element that will not be used when the terminal is in an RRC inactive state and can be paged by the first access network device, further improving the utilization rate of the stored downlink data and alleviating the data storage pressure on the third network element.

[0183] The following describes an implementation of the communication method shown in Figure 3, combining the paging process of the first access network device paging the terminal, and taking the first network element as AMF, the second network element as SMF, and the third network element as UPF as an example. As shown in Figure 7, the implementation includes:

[0184] S701, SMF sends a first subscription request to AMF, where the first subscription request is used to subscribe the terminal to enter the RRC inactive state; accordingly, AMF receives the first subscription request.

[0185] S702, after determining that the terminal enters the RRC inactive state, the AMF sends a first notification message to the SMF, where the first notification message is used to indicate that the terminal enters the RRC inactive state; accordingly, the SMF receives the first notification message.

[0186] S703, in response to the terminal being in an RRC inactive state, the SMF sends a first indication message to the UPF, where the first indication message is used to instruct the UPF to store the downlink data sent to the terminal; accordingly, the UPF receives the first indication message.

[0187] S704: The UPF receives downlink data from the AF that needs to be sent to the terminal.

[0188] S705: The UPF stores the downlink data sent to the terminal based on the first indication information.

[0189] For the description of steps S701 to S705 , reference may be made to the above description of steps S301 to S306 , which will not be detailed here.

[0190] S706, UPF sends the downlink data to the first access network device, which is the access network device that last served the terminal (last gNB). Accordingly, the first access network device receives the downlink data.

[0191] In an embodiment of the present application, the terminal is in an RRC inactive state, and the UPF assumes that the first access network device can page the terminal, so the UPF will send the downlink data that needs to be sent to the terminal to the first access network device, so that the downlink data can be sent to the terminal through the first access network device.

[0192] As an example, the downlink data sent to the terminal originates from the P-CSCF. For example, in response to a voice call initiated by the calling user, the P-CSCF sends an invite request (downlink data) to the UPF. After receiving the invite request, the UPF encapsulates the invite request into a GTP-U message and sends it to the last gNB. It should be noted that this downlink data can also be other service requests sent by the AF to the UPF in addition to the invite request, and this document does not limit this.

[0193] It should be noted that steps S706 and S705 can be executed simultaneously or sequentially, and this application does not limit the order in which they are executed.

[0194] S707 : The first access network device pages the terminal through RAN paging in response to the downlink data, but the paging result is paging failure.

[0195] In this embodiment of the present application, a terminal is in an RRC inactive state and is connected to a second access network device (also referred to as a new gNB). This second access network device is different from the first access network device (the last gNB). After receiving downlink data, the last gNB triggers RAN paging to page the terminal within the RAN Notification Area (RNA) to which the terminal belongs.

[0196] For example, if the terminal belongs to RNA1, the last gNB, in addition to paging the terminal within its own communication range, also notifies other base stations within RNA1, including the new gNB, of the terminal's paging request over the Xn interface. However, due to a failure in the Xn interface between the last gNB and the new gNB, the last gNB may be unable to notify the new gNB of the terminal's paging request over the Xn interface. After determining that the paging has timed out (i.e., the terminal is unreachable), the last gNB determines that the paging has failed. Due to the paging timeout, the last gNB discards the downlink data required for transmission.

[0197] S708, the first access network device sends an N2UE context release request message to the AMF; accordingly, the AMF receives the N2UE context release request message.

[0198] In an embodiment of the present application, the first access network device sends an N2UE context release request message to the AMF based on the paging result of the paging terminal being a paging failure. The N2UE context release request message can trigger the core network to execute a process of releasing the user plane resources of the terminal.

[0199] As an example, the N2UE context release request message may be used to indicate that the paging result of the terminal through the first access network device is a paging failure, and / or to indicate the release of the user plane resources of the terminal, wherein the user plane resources include access network tunnel information and core network tunnel information.

[0200] S709: The core network releases user plane resources of the terminal.

[0201] As an example, step S709 includes:

[0202] S7091, in response to the N2UE context release request, AMF sends a Nsmf_PDUSession_UpdateSMContext request message to SMF, where the Nsmf_PDUSession_UpdateSMContext request message is used to request SMF to release the user plane resources of the terminal.

[0203] In some possible implementations, the Nsmf_PDUSession_UpdateSMContext request message may also be used to request the SMF to release user plane resources corresponding to one or more session identifiers (the one or more PDU sessions correspond to the terminal).

[0204] In some possible implementations, the Nsmf_PDUSession_UpdateSMContext request message may indicate that the paging result of the first access network device paging the terminal is a paging failure, or indicate that the terminal is in the RRC inactive state and the paging result of the first access network device paging the terminal is a paging failure.

[0205] S7092, in response to the Nsmf_PDUSession_UpdateSMContext request, the SMF sends an N4 session modification request to the UPF, where the N4 session modification request is used to request the UPF to release the user plane resources of the terminal.

[0206] In some possible implementations, the N4 session modification request may also be used to request the UPF to release user plane resources of one or more PDU sessions corresponding to one or more session identifiers (the one or more PDU sessions correspond to the terminal).

[0207] In some possible implementations, the N4 session modification request may also indicate that the paging result of the first access network device paging the terminal is a paging failure, or indicate that the terminal is in the RRC inactive state and the paging result of the first access network device paging the terminal is a paging failure. It should be noted that the Nsmf_PDUSession_UpdateSMContext request message and the N4 session modification request generally do not carry information that the paging result of the first access network device paging the terminal is a paging failure. The method provided in this application can enable the SMF and UPF to perceive the information of the terminal paging failure, so that the SMF can better decide the timing of instructing the UPF to store downlink data, and can also facilitate the UPF to better decide the timing of storing downlink data based on the first indication information sent by the SMF.

[0208] S7093, UPF replies to SMF with an N4 session modification response message, where the N4 session modification response message is used to indicate the user plane resources of the terminated terminal.

[0209] In an embodiment of the present application, after the UPF responds to the N4 session modification request sent by the SMF to request the UPF to release the user plane resources of the terminal, it terminates the N3 user plane resources of the terminal, and responds to the N4 session modification request and replies to the SMF with an N4 session modification response message to indicate that the user plane resources are released successfully.

[0210] S7094, SMF sends an Nsmf_PDUSession_UpdateSMContext request response message to AMF to indicate that the user plane resources of the terminal have been terminated.

[0211] In an embodiment of the present application, after SMF receives the N4 session modification response message sent by UPF to indicate the N3 user plane resources of the terminated terminal, it sends an Nsmf_PDUSession_UpdateSMContext request response message to AMF, and the Nsmf_PDUSession_UpdateSMContext request response message is used to indicate the N3 user plane resources of the terminated terminal to AMF.

[0212] S710, AMF initiates core network paging to the terminal.

[0213] S711: The terminal enters the CM connection state based on the core network paging and service request process.

[0214] Among them, the terminal entering the CM connection state includes configuring user plane resources serving the terminal between the UPF and the second access network device (the second access network device is the base station currently accessed by the terminal, also known as new gNB), or configuring user plane resources for one or more PDU sessions serving the terminal between the UPF and the second access network device.

[0215] For detailed descriptions of steps S707 to S711 , please refer to the relevant descriptions in the corresponding communication protocol standards, which will not be detailed here.

[0216] S712, UPF sends the stored downlink data to the terminal; correspondingly, the terminal receives the downlink data.

[0217] For the description of step S712, please refer to the relevant description of step S307 above, which will not be described in detail here.

[0218] In some possible implementations, the first subscription request is also used to subscribe the terminal to enter the CM connection state. After the SMF obtains information from the AMF that the terminal has entered the CM connection state based on the first subscription request, the SMF sends second indication information to the UPF, instructing the UPF to no longer store downlink data from the terminal if it receives it again, and / or instructing the UPF to delete the stored data sent to the terminal. For an explanation of the second indication information, please refer to the relevant description elsewhere in this document and will not be detailed here.

[0219] Using the communication method provided in the embodiment of the present application, after the terminal enters the RRC inactive state, the SMF sends a first indication message to the UPF to instruct the UPF to store the downlink data sent to the terminal. After receiving the downlink data sent to the terminal, the UPF stores the downlink data based on the first indication message. In addition, after the terminal switches from the RRC inactive state to the CM idle state and finally enters the CM connected state, the UPF directly sends the stored downlink data to the terminal without waiting for the timeout retransmission of the downlink data. On the one hand, the service delay in this scenario can be reduced; on the other hand, the decision-making task of determining the need to store data based on the terminal entering the RRC inactive state is implemented by the SMF side, which facilitates the unified management of decision-making services and reduces the decision-making management functions on the UPF side.

[0220] In some other possible implementations, the above-mentioned step S703 (SMF sends a first indication message to the UPF in response to the terminal being in an RRC inactive state) may include: when the SMF determines that the terminal is in an RRC inactive state and determines that the paging result of the terminal paging based on the first access network device is a paging failure, sending a first indication message to the UPF, and the first indication message is used to instruct the UPF to store the downlink data sent to the terminal.

[0221] In this method, as an example, the step S703 can be executed after the above-mentioned step S7091. For example, the SMF determines that the paging result of the paging terminal based on the first access network device is a paging failure based on the Nsmf_PDUSession_UpdateSMContext request message received in step S4091, and then triggers the execution of step S703 to send the above-mentioned first indication information to the UPF. It should be noted that, in this method, the step S703 and the above-mentioned step S7092 can be executed simultaneously or successively, and the order of sequence is not limited. In some possible implementation methods, the first indication information can also be included in the N4 session modification request in step S7091 and sent to the UPF.

[0222] With this approach, the SMF instructs the UPF to store the terminal's downlink data only after determining that the terminal is in the RRC inactive state and that the paging result from the first access network device is a paging failure. After the terminal enters the CM connected state, the UPF directly sends the stored downlink data to the terminal, reducing service latency. Furthermore, this can further improve the utilization rate of stored downlink data, reduce unnecessary storage overhead, and alleviate data storage pressure on the UPF.

[0223] In some other possible implementations, the above-mentioned step S705 (UPF stores downlink data sent to the terminal based on the first indication information) may include: when the UPF determines that the paging result of the terminal paging based on the first access network device is a paging failure, the UPF stores the data based on the first indication information.

[0224] In this approach, as an example, step S705 can be performed after step S7092. For example, based on the N4 session modification request received in step S7093, the UPF determines that the paging result of the terminal paging based on the first access network device is a paging failure, thereby triggering the UPF in step S705 to store downlink data based on the first indication information. It should be noted that in this approach, step S705 and step S7093 can be performed simultaneously or sequentially, and the order of execution is not limited.

[0225] Using this method, the UPF stores downlink data based on the first indication information only when it determines that the paging result of the terminal based on the first access network device is a paging failure. This can reduce the service delay in this scenario while further improving the utilization rate of the stored downlink data and reducing unnecessary storage overhead.

[0226] In some other communication methods, when the UPF receives downlink data again (for example, the downlink data may be retransmission data of the downlink data corresponding to step S706, or another downlink data sent to the terminal different from the downlink data), the UPF has not received the notification of UE paging failure before, resulting in the UPF not perceiving that the core network is trying to migrate the UE from the RRC inactive state to the CM idle state and then to the CM connected state. Therefore, the UPF will trigger the relevant processes of steps S201-S203 shown in Figure 2 again based on the downlink data, causing unnecessary communication pressure on the communication system.

[0227] In view of this, in some other possible implementations, when the UPF determines that the terminal is in an RRC inactive state and the paging result of the terminal paging based on the first access network device is a paging failure, the UPF will no longer trigger the UE's RAN paging for the downlink data that needs to be sent to the terminal that is received by the UPF, but will directly store the downlink data. And after the terminal enters the CM connection state in step S711, the downlink data that needs to be sent to the terminal will be sent to the terminal through the second access network device. In this way, the problem of the UPF triggering the paging terminal multiple times in adjacent time periods for multiple downlink data sent to the same terminal, causing unnecessary communication pressure on the communication system, is avoided. It should be noted that this method is not only applicable to the communication method shown in Figure 7 but also to other embodiments of this article, and this article does not limit this.

[0228] The following combines the first indication information sent by the SMF to the UPF as a first notification message (used to notify the UPF that the terminal enters the RRC inactive state), and takes the first network element as the AMF, the second network element as the SMF, and the third network element as the UPF as an example to introduce another implementation of the communication method shown in Figure 3. As shown in Figure 8, the implementation method includes:

[0229] S801, UPF sends a first subscription request to SMF, where the first subscription request is used to subscribe the terminal to enter the RRC inactive state. Correspondingly, SMF receives the first subscription request from UPF.

[0230] As an example, UPF can subscribe to SMF through a service message, such as Nupf_EventExposure_Subscribe.

[0231] As an example, the UPF may send the first subscription request to the SMF during the PDU session establishment process initiated by the terminal. It should be noted that if the UPF has already sent the first subscription request to the SMF when the terminal initiates the PDU session establishment process, the second network element may no longer send the first subscription request repeatedly.

[0232] S802, SMF sends a first notification message to UPF, where the first notification message is used to instruct the terminal to enter the RRC inactive state. Accordingly, UPF receives the first notification message from SMF.

[0233] As an example, the SMF may send the second notification message to the UPF through a service message, such as Nupf_EventExposure_Notify, or through an N4 message, to notify the UPF that the terminal has entered the RRC inactive state.

[0234] In some possible implementations, the UPF sending the first subscription request to the SMF indicates that the UPF directly subscribes to the SMF for the information that the terminal enters the RRC inactive state. In this manner, after receiving the first subscription request, the SMF may subscribe to the information that the terminal enters the RRC inactive state from the AMF, and after obtaining the information that the terminal enters the RRC inactive state, send the first notification message to the UPF.

[0235] In some other possible implementations, UPF sends a first subscription request to SMF, indicating that UPF subscribes to AMF through SMF for information that the terminal enters the RRC inactive state. In this way, after receiving the first subscription request, SMF can directly forward the first subscription request to AMF. And after receiving the first notification message from AMF, SMF forwards the first notification message to UPF. Alternatively, after receiving the first subscription request, SMF can also subscribe to AMF for information that the terminal enters the RRC inactive state, and after obtaining the information that the terminal enters the RRC inactive state, it sends a first notification message to UPF. For instructions on SMF subscribing to AMF for the terminal entering the RRC inactive state, please refer to steps S301 to S303 above, which will not be described in detail here.

[0236] For the description of the first subscription request and the first notification message, please refer to the relevant description of steps S301 to S303 above, which will not be described in detail here.

[0237] S803: The UPF receives downlink data from the AF that needs to be sent to the terminal.

[0238] S804: UPF stores the downlink data based on the terminal being in an RRC inactive state.

[0239] In an embodiment of the present application, after determining that the terminal is in an RRC inactive state, if the UPF receives downlink data sent to the terminal, it actively triggers the storage of the downlink data.

[0240] S805, UPF sends the downlink data to the first access network device, which is the access network device that last served the terminal; accordingly, the first access network device receives the downlink data.

[0241] S806: The first access network device pages the terminal through RAN paging in response to the downlink data, but the paging result is paging failure.

[0242] S807, the first access network device sends an N2UE context release request message to the AMF; accordingly, the AMF receives the N2UE context release request message.

[0243] S808: The core network releases user plane resources of the terminal.

[0244] In response to the UE context release request message, the core network releases the user plane resources of the terminal and migrates the terminal from the RRC inactive state to the CM idle state.

[0245] S809, AMF initiates core network paging to the terminal.

[0246] S810: The terminal enters a CM connection state based on the core network paging and service request process.

[0247] S811, UPF sends the stored downlink data to the terminal; correspondingly, the terminal receives the downlink data.

[0248] Regarding steps S803 to S811, reference may be made to the relevant descriptions of other embodiments herein, for example, reference may be made to the relevant descriptions of steps S704 to S712 above, and no further details will be given here.

[0249] Using the communication method provided in the embodiments of the present application, after determining that the terminal has entered the RRC Inactive state, the UPF receives downlink data sent to the terminal and stores the downlink data. After the terminal switches from the RRC Inactive state to the CM Idle state and finally enters the CM Connected state, the UPF directly sends the stored downlink data to the terminal without waiting for the downlink data to time out and be retransmitted, thereby reducing service latency in this scenario.

[0250] In some other possible implementations, the above-mentioned step S804 (UPF stores the downlink data based on the terminal being in an RRC inactive state) may include: when the UPF determines that the terminal is in an RRC inactive state and the paging result of the first access network device to the terminal is a paging failure, the UPF stores the downlink data, and the first access network device is the access network device that the terminal last accessed.

[0251] In this manner, as an example, step S804 may be executed after the UPF receives the N4 session modification request from the SMF instructing the release of the user plane resources of the terminal in the above-mentioned step S808 (refer to step S7092). For example, based on the received N4 session modification request, the UPF determines that the paging result of the terminal based on the first access network device is a paging failure, thereby triggering the storage of downlink data. It should be noted that in this manner, step S804 and the step of the UPF receiving the N4 session modification request in S808 may be executed simultaneously or successively, and the order of the steps is not limited.

[0252] Using this method, the UPF stores the terminal only when it determines that the terminal is in an RRC inactive state and the paging result of the terminal based on the first access network device is a paging failure. This can reduce service latency while further improving the utilization rate of stored downlink data and reducing unnecessary storage overhead.

[0253] The following describes an implementation of the communication method shown in Figure 6, combining the paging process of the first access network device paging the terminal, and taking the first network element as AMF, the second network element as SMF, and the third network element as UPF as an example. As shown in Figure 9, the implementation includes:

[0254] S901: UPF receives downlink data from AF that needs to be sent to the terminal.

[0255] S902, UPF sends the downlink data to the first access network device, which is the access network device that last served the terminal. Correspondingly, the first access network device receives the downlink data from UPF.

[0256] In an embodiment of the present application, the terminal is in an RRC inactive state, and the UPF assumes that the first access network device can page the terminal, so the UPF will send the downlink data that needs to be sent to the terminal to the first access network device, so that the downlink data can be sent to the terminal through the first access network device.

[0257] S903: The first access network device pages the terminal through RAN paging in response to the downlink data, but the paging result is paging failure.

[0258] S904, the first access network device sends an N2UE context release request message to the AMF, and accordingly, the AMF receives the N2UE context release request message.

[0259] In an embodiment of the present application, the N2UE context release request message is used to indicate that the paging result of the terminal through the first access network device (last gNB) is a paging failure, and / or to indicate the release of the user plane resources of the terminal, or it can also be understood as triggering the core network to release the user plane resources of the UE.

[0260] S905, in response to the N2UE context release request, the AMF sends a Nsmf_PDUSession_UpdateSMContext request message to the SMF, where the Nsmf_PDUSession_UpdateSMContext request message is used to request the SMF to release the user plane resources of the terminal.

[0261] S906, SMF sends a second subscription request to UPF in response to the Nsmf_PDUSession_UpdateSMContext request message, where the second subscription request is used to request notification of receipt of downlink data sent to the terminal.

[0262] In an embodiment of the present application, the SMF determines, based on the Nsmf_PDUSession_UpdateSMContext request message, that the terminal is in an inactive state and cannot be paged to the terminal based on the first access network device, then the SMF sends a second subscription request to the UPF, where the second subscription request is used to request the UPF to send a related subscription notification to the SMF after receiving the downlink data sent to the terminal. The second subscription request includes a method for subscribing to the UPF receiving the above-mentioned downlink data again.

[0263] S907: UPF receives downlink data from AF that needs to be sent to the terminal.

[0264] In an embodiment of the present application, it can also be understood that the downlink data received by the UPF in step S907 may be retransmission data of the downlink data in step S901, or the downlink data received by the UPF in step S907 may also be another downlink data that needs to be sent to the terminal, which is different from the downlink data in step S901. This document does not limit this.

[0265] S908, in response to the second subscription request, the UPF sends a third notification message to the SMF, where the third notification message is used to indicate that downlink data sent to the terminal has been received; accordingly, the SMF receives the third notification message.

[0266] S909, SMF sends third indication information to UPF in response to the third notification message, and the third indication information is used to store the downlink data; accordingly, UPF receives the third indication information.

[0267] S910, UPF stores the downlink data based on the third indication information.

[0268] Regarding steps S906 to S910, reference may be made to the relevant descriptions of steps S601 to S605 above, and no further details will be given here.

[0269] S911: The core network releases user plane resources of the terminal.

[0270] In response to the UE context release request message, the core network releases the user plane resources of the terminal and migrates the terminal from the RRC inactive state to the CM idle state.

[0271] The step S911 may include the above steps S7092 to S7094.

[0272] It should be noted that the above step S906 can be executed after step S905, and S906 and S7092 in S911 can be executed simultaneously or successively, and the order is not limited.

[0273] S912, AMF initiates core network paging to the terminal.

[0274] S913: The terminal enters the CM connection state based on the core network paging and service request process.

[0275] S914, UPF sends the stored downlink data to the terminal; correspondingly, the terminal receives the downlink data.

[0276] For the relevant descriptions of steps S911 to S914, reference may be made to the relevant descriptions of other embodiments herein, for example, reference may be made to the relevant descriptions of steps S709 to S712 above, and will not be detailed here.

[0277] Using the communication method provided in the embodiments of the present application, after the SMF determines that the terminal is in the inactive state based on the N2UE context release request message and that the paging result of the terminal paging by the first access network device is a paging failure, it subscribes to the UPF to determine whether downlink data sent to the terminal has been received. After receiving the second notification message sent by the UPF, the SMF instructs the UPF to store the downlink data of the terminal. Therefore, after the UPF determines that the terminal has entered the CM connection state, if the UPF has stored the downlink data, it can send the stored downlink data to the terminal as soon as possible, thereby reducing service latency in this scenario.

[0278] The following describes another implementation of the communication method shown in Figure 6, combining the paging process of the first access network device paging the terminal, and taking the first network element as AMF, the second network element as SMF, and the third network element as UPF as an example. As shown in Figure 10, this implementation includes:

[0279] S1001, SMF sends a first subscription request to AMF, where the first subscription request is used to subscribe the terminal to enter the RRC inactive state; accordingly, AMF receives the first subscription request.

[0280] S1002: After determining that the terminal enters the RRC inactive state, the AMF sends a first notification message to the SMF based on the first subscription request. The first notification message is used to notify the terminal to enter the RRC inactive state.

[0281] The description of steps S1001 and S1002 can refer to the relevant description of steps S301 to S303 above, and will not be described in detail here.

[0282] S1003, in response to the terminal entering the RRC inactive state, the SMF sends a second subscription request to the UPF, where the second subscription request is used to request notification of receipt of downlink data sent to the terminal; accordingly, the UPF receives the second subscription request.

[0283] S1004, UPF receives downlink data sent to the terminal.

[0284] S1005. In response to the second subscription request, the UPF sends a third notification message to the SMF, where the third notification message is used to indicate that downlink data sent to the terminal has been received; accordingly, the SMF receives the third notification message.

[0285] S1006, SMF sends third indication information to UPF in response to the third notification message, and the third indication information is used to store the downlink data; accordingly, UPF receives the third indication information.

[0286] S1007, UPF stores the downlink data based on the third indication information.

[0287] For the relevant descriptions of the second subscription request, the third notification message, and the third indication information in steps S1003 to S1007, please refer to the relevant descriptions above, for example, please refer to the relevant descriptions in steps S601 to S605 above, which will not be described in detail here.

[0288] S1008, UPF sends the downlink data to the first access network device, and accordingly, the first access network device receives the downlink data.

[0289] It should be noted that step S1008 can be executed after step S1004. For example, it can be executed simultaneously with step S1005 or executed one after the other, and the order of execution is not limited.

[0290] S1009: The first access network device pages the terminal through RAN paging in response to the downlink data, but the paging result is paging failure.

[0291] S1010, the first access network device sends an N2UE context release request message to the AMF, and accordingly, the AMF receives the N2UE context release request message.

[0292] S1011: The core network releases user plane resources of the terminal.

[0293] In response to the UE context release request message, the core network releases the user plane resources of the terminal and migrates the terminal from the RRC inactive state to the CM idle state.

[0294] S1012, AMF initiates core network paging to the terminal.

[0295] S1013: The terminal enters the CM connection state based on the core network paging and service request process.

[0296] S1014, UPF sends the stored downlink data to the terminal; correspondingly, the terminal receives the downlink data.

[0297] The description of steps S1008-S1014 can also refer to the relevant description in the above embodiment, for example, the relevant description of steps S706-S712 can be referred to, and will not be described in detail here.

[0298] Using the communication method provided in the embodiments of the present application, after the SMF determines that the terminal is in the RRC inactive state, it subscribes to the UPF to determine whether it has received downlink data sent to the terminal. After receiving the second notification message sent by the UPF, the SMF instructs the UPF to store the downlink data of the terminal. Therefore, after the UPF determines that the terminal has entered the CM connected state, if the UPF has stored the downlink data, it can send the stored downlink data to the terminal as soon as possible, thereby reducing service latency in this scenario.

[0299] In some other possible implementations, the SMF or AMF may also request to subscribe to the downlink data of the terminal received by the UPF when the terminal is in the RRC inactive state, the CM connected state, or the CM idle state, and send an indication to the UPF to store the downlink data when receiving the notification message of the downlink data of the terminal sent by the UPF and determining that the terminal is in the RRC inactive state (or determining that the terminal is in the RRC inactive state and the first access network device fails to page the terminal).

[0300] In some other communication methods provided in the embodiments of the present application, the SMF may also instruct the UPF to store downlink data sent to the terminal when the terminal is in the CM idle state or in the CM connected state (including the CM connected state or the CM idle state). For example, as shown in Figure 11, the communication method includes:

[0301] S1101: The core network creates a PDU session related to the terminal.

[0302] The PDU session may be the first PDU session of the terminal.

[0303] S1102, SMF sends a first indication message to UPF during the session establishment process of the terminal, and the first indication message is used to store the downlink data sent to the terminal; accordingly, UPF receives the first indication message.

[0304] In an embodiment of the present application, the first indication information is used to instruct the UPF to store downlink data sent to the terminal.

[0305] In an embodiment of the present application, the SMF may send the first indication information to the UPF during the PDU session establishment process of the terminal. However, it should be noted that before the PDU session establishment process of the terminal, if the second network element has already sent the first indication information to the first network element, the SMF may not repeatedly send the first indication information to the UPF.

[0306] In an embodiment of the present application, the SMF can instruct the UPF based on the first indication information to store the downlink data sent to the terminal whether the terminal is in the CM idle state or in the CM connected state (including the CM connected state or the CM idle state).

[0307] S1103: The UPF receives downlink data from the AF that needs to be sent to the terminal.

[0308] S1104: The UPF stores the downlink data sent to the terminal based on the first indication information.

[0309] S1105, UPF sends the downlink data to the first access network device, and accordingly, the first access network device receives the downlink data.

[0310] S1106: The first access network device pages the terminal through RAN paging in response to the downlink data, but the paging result is paging failure.

[0311] S1107, the first access network device sends an N2UE context release request message to the AMF.

[0312] S1108: The core network releases user plane resources of the terminal.

[0313] In response to the UE context release request message, the core network releases the user plane resources of the terminal and migrates the terminal from the RRC inactive state to the CM idle state.

[0314] S1109, AMF initiates core network paging to the terminal.

[0315] S1110: The terminal enters a CM connection state based on the core network paging and service request process.

[0316] S1111, UPF sends the stored downlink data to the terminal; correspondingly, the terminal receives the downlink data.

[0317] For the relevant descriptions of steps S1103 to S1111, please refer to the relevant descriptions of other embodiments in this document, for example, please refer to the relevant descriptions of steps S704 to S712 above, and will not be described in detail here.

[0318] In some other communication methods provided in embodiments of the present application, the UPF may also proactively store all downlink data sent to the terminal when the terminal is in the CM idle state or the CM connected state. Referring to Figure 11 , this method may sequentially include steps S1101, S1112, S1103, S1113, and S1105-S1111. S1112 may be the UPF determining to store downlink data sent to the terminal based on the terminal's session establishment process. S1113 may be the UPF proactively storing the downlink data sent to the terminal based on step S1112.

[0319] Using the communication method provided in the embodiments of the present application, the UPF stores downlink data sent to the terminal when the terminal is in either the CM Idle state or the CM Connected state. Therefore, after the terminal enters the CM Idle state and then the CM Connected state from the RRC Inactive state, the UPF can immediately send the stored downlink data to the terminal, reducing service latency in this scenario.

[0320] In some other communication schemes, when a terminal is in CM Idle state, a third network element receives downlink data destined for the terminal. Because the third network element knows that the terminal is in CM Idle state and therefore unreachable via the last gNB, it stores the downlink data and then sends it to the terminal after the terminal switches from CM Idle to CM Connected state. However, this scheme does not store the downlink data when the terminal is in RRC Inactive state. This is because when the terminal is in RRC Inactive state, the third network element is unaware that the terminal has lost its connection to the last gNB and assumes that the last gNB can page the terminal. In other words, this solution can be understood as a technical evolution based on this method, which solves the problem that in the scenario where the terminal is in the RRC inactive state and is unreachable, during the process of the terminal switching from the RRC inactive state to the CM idle state, the third network element did not store the downlink data received for the first time when the terminal was in the RRC inactive state, and the third network element did not store the retransmission data corresponding to the downlink data during the process of the terminal switching from the RRC inactive state to the CM idle state, as well as the timeout retransmission duration of the downlink data and the duration of the terminal migrating from the RRC inactive state to the RRC idle state and then entering the connected state, there is no relevant duration matching design between the two durations, resulting in the terminal switching from the RRC inactive state to the CM idle state and then from the CM idle state to the CM connected state. The terminal needs to wait for the retransmission of the downlink data before it can successfully receive the service delay of the downlink data.

[0321] Based on the same concept of the above communication method, the present application also provides the following communication device:

[0322] Figure 12 shows a schematic diagram of the structure of a possible communication device. It is understandable that the communication device 120 includes necessary forms (means) such as modules, units, elements, circuits, or interfaces, which are appropriately configured together to implement the present solution. The communication device 120 can be the RAN node or terminal device in Figure 1, or a component (such as a chip) in these devices, used to implement the method described in the above method embodiment. The communication device 120 includes one or more processors 121 (one processor is shown in the figure). The processor 121 can be a general-purpose processor or a dedicated processor. For example, it can be a baseband processor or a central processing unit. The baseband processor can be used to process communication protocols and communication data, and the central processing unit can be used to control the communication device (such as a RAN node, terminal device, or chip, etc.), execute software programs, and process software program data.

[0323] Optionally, in one design, the processor 121 may include a program 123 (sometimes also referred to as code or instructions), which may be executed on the processor 121 to enable the communication device 120 to perform the methods described in the above embodiments. In another possible design, the communication device 120 includes a circuit (not shown in FIG. 12 ) that is configured to implement the functions of the network device or terminal device in the above embodiments.

[0324] Optionally, the communication device 120 may include one or more memories 122 (one memory is illustrated in the figure), on which a program 124 (sometimes also referred to as code or instructions) is stored. The program 124 can be run on the processor 121, so that the communication device 120 executes the method described in the above method embodiment.

[0325] Optionally, the processor 121 and / or the memory 122 may include an artificial intelligence (AI) module 127 and an AI module 128, which are used to implement AI-related functions. The AI ​​module can be implemented through software, hardware, or a combination of software and hardware. For example, the AI ​​module may include a radio access network intelligent controller (RAN intelligent controller, RIC) module. For example, the AI ​​module may be a near real-time RIC or a non-real-time RIC.

[0326] Optionally, data may be stored in the processor 121 and / or the memory 122. The processor and the memory may be provided separately or integrated together.

[0327] Optionally, the communication device 120 may further include a transceiver 125 and / or an antenna 126. The processor 121 may also be sometimes referred to as a processing unit, and controls the communication device (e.g., a RAN node or terminal device). The transceiver 125 may also be sometimes referred to as a transceiver unit, a transceiver, a transceiver circuit, or a transceiver, and is configured to implement the transceiver functions of the communication device via the antenna 126. For example, the transceiver 125 may include a receiver and a transmitter, which may be integrated or independent components.

[0328] As an example, when the communication device 120 is used to implement the functions of a third network element, the receiver is used to implement the receiving actions in steps S304 and / or S305 in the embodiment shown in Figure 3 , the transmitter is used to implement the sending action in step S307 in the embodiment shown in Figure 3 , and the memory 122 is used to implement the storing action in step S306 in the embodiment shown in Figure 3 . Alternatively, the receiver is used to implement the receiving actions in one or more of steps S601, S602, and S604 in the embodiment shown in Figure 6 , the transmitter is used to implement the sending action in step S606 in the embodiment shown in Figure 6 , and the memory 122 is used to implement the storing action in step S605 in the embodiment shown in Figure 6 . This communication device can also be used to implement the functions of the UPF in the embodiments shown in Figures 7 to 11 , which will not be described in detail here.

[0329] As another example, when the communication device 120 is used to implement the function of the second network element, the transmitter is used to implement the actions of sending in steps S301 and / or S304 in the embodiment shown in Figure 3, and the receiver is used to implement the actions of receiving in step S303 in the embodiment shown in Figure 3. The remaining steps in the embodiment, such as the generation of the first subscription request and the first indication information, are implemented by the processor 121. Alternatively, the transmitter is used to implement the actions of sending in steps S601 and / or S604 in the embodiment shown in Figure 6, and the receiver is used to implement the actions of receiving in step S603 in the embodiment shown in Figure 6. The remaining steps in the embodiment, such as the generation of the second subscription request and the third indication information, are implemented by the processor 121. The communication device can also be used to implement the functions of the SMF in the embodiments shown in Figures 7 to 11, which will not be described in detail.

[0330] As another example, when the communication device is used to implement the function of the first network element, the transmitter is used to implement the action of sending in step S303 in the embodiment shown in Figure 3, and the receiver is used to implement the action of receiving in step S301 in the embodiment shown in Figure 3. In the embodiment, the remaining steps such as determining that the terminal enters the RRC inactive state are implemented by the processor 121, or are performed in cooperation with the processor 121, the receiver, and the transmitter. The communication device can also be used to implement the functions of the first network element and the AMF in the embodiments shown in Figures 6 to 11, which will not be described in detail one by one.

[0331] As shown in Figure 13, it is a structural diagram of another communication device provided in an embodiment of the present application, and the communication device 1300 includes a processor 1301. Optionally, the communication device 1300 may further include an interface circuit 1302 (indicated by a dotted line in the figure), and the processor 1301 and the interface circuit 1302 are coupled to each other. It will be understood that the interface circuit 1302 may be a transceiver or an input / output interface. Optionally, the communication device 1300 may further include a memory 1303 (indicated by a dotted line in the figure), and the memory 1303 is used to store instructions executed by the processor 1301, or to store input data required for the processor 1301 to run the instructions, or to store data generated after the processor 1301 runs the instructions. Among them, the processor 1301 is used to implement the function of the processor 121 in the embodiment shown in Figure 12 above; and the interface circuit 1302 is used to implement the function of the transceiver 125 in the embodiment shown in Figure 12 above.

[0332] As an example, when the above-mentioned communication device is a chip applied to a third network element, the chip implements the functions of the third network element in the above-mentioned method embodiment. The chip receives information from other modules (such as a radio frequency module or antenna) in the third network element, and the information is sent by the second network element, the first network element, or the AF to the network device; or, the chip sends information through other modules (such as a radio frequency module or antenna), and the information is sent by the third network element to the second network element, the first network element, or the access network device.

[0333] As another example, when the above-mentioned communication device is a chip applied to a second network element, the chip implements the functions of the second network element in the above-mentioned method embodiment. The chip receives information from other modules (such as a radio frequency module or antenna) in the second network element, and the information is sent to the network device by the first network element or the third network element; or the chip sends information through other modules (such as a radio frequency module or antenna), and the information is sent by the second network element to the first network element or the third network element.

[0334] As another example, when the above-mentioned communication device is a chip applied to a first network element, the chip implements the functions of the first network element in the above-mentioned method embodiment. The chip receives information from other modules (such as a radio frequency module or antenna) in the first network element, and the information is sent by the second network element, the third network element, or the access network device to the network device; or the chip sends information through other modules (such as a radio frequency module or antenna), and the information is sent by the first network element to the second network element, the third network element, or the access network device.

[0335] In addition, it should be noted that the aforementioned transceiver unit and / or processing unit may be implemented through virtual modules, for example, the processing unit may be implemented through a software function unit or a virtual device, and the transceiver unit may be implemented through a software function or a virtual device. Alternatively, the processing unit or transceiver unit may also be implemented through a physical device, for example, if the device is implemented using a chip / chip circuit, the transceiver unit may be an input / output circuit and / or a communication interface, performing input operations (corresponding to the aforementioned receiving operations) and output operations (corresponding to the aforementioned sending operations); the processing unit is an integrated processor or microprocessor or integrated circuit.

[0336] As shown in FIG14 , it is a schematic diagram of the structure of another communication device provided in an embodiment of the present application. The communication device 1400 includes a transceiver unit 1401 and a processing unit 1402.

[0337] Illustratively, the transceiver unit 1401 may include a receiving unit and a sending unit, and the receiving unit and the sending unit may be an integrated unit or independent units.

[0338] As an example, when the communication device 1400 is used to implement the function of the third network element, the receiving unit is used to implement the receiving action in steps S304 and / or S305 in the embodiment shown in Figure 3, the sending unit is used to implement the sending action in step S307 in the embodiment shown in Figure 3, and the storage action in step S306 in the embodiment shown in Figure 3 is implemented by the processing unit 1402 or by an additional memory. Alternatively, the receiving unit is used to implement the receiving action in one or more of steps S601, S602, and S604 in the embodiment shown in Figure 6, the sending unit is used to implement the sending action in step S606 in the embodiment shown in Figure 6, and the storage action in step S605 in the embodiment shown in Figure 6 is implemented by the processing unit 1402 or by an additional memory. The communication device 1400 can also be used to implement the functions of the UPF in the embodiments shown in Figures 7 to 11, which will not be described in detail one by one.

[0339] As another example, when the communication device 1400 is used to implement the function of the second network element, the sending unit is used to implement the sending action in steps S301 and / or S304 in the embodiment shown in FIG3 , the receiving unit is used to implement the receiving action in step S303 in the embodiment shown in FIG3 , and the remaining steps in the embodiment, such as the generation of the first subscription request and the first indication information, are implemented by the processing unit 1402. Alternatively, the sending unit is used to implement the sending action in steps S601 and / or S604 in the embodiment shown in FIG6 , the receiving unit is used to implement the receiving action in step S603 in the embodiment shown in FIG6 , and the remaining steps in the embodiment, such as the generation of the second subscription request and the third indication information, are implemented by the processing unit 1402. The communication device can also be used to implement the functions of the SMF in the embodiments shown in FIG7 to FIG11 , which will not be described in detail.

[0340] As another example, when the communication device is used to implement the function of the first network element, the sending unit is used to implement the sending action in step S303 of the embodiment shown in Figure 3, and the receiving unit is used to implement the receiving action in step S301 of the embodiment shown in Figure 3. In the embodiment, the remaining steps such as determining that the terminal enters the RRC inactive state are implemented by the processing unit 1402, or are performed in cooperation with the processing unit 1402, the receiving unit, and the sending unit. The communication device can also be used to implement the functions of the first network element and the AMF in the embodiments shown in Figures 6 to 11, which will not be described in detail one by one.

[0341] For the implementation of the above-mentioned transceiver unit 1401 and the processing unit 1402, reference may be made to the relevant descriptions in the embodiments shown in FIG. 3 to FIG. 11 .

[0342] The division of modules in this application is illustrative and represents only a logical functional division. In actual implementation, other division methods may be used. Furthermore, the functional modules in the examples of this application may be integrated into a single processor, exist physically as separate modules, or two or more modules may be integrated into a single module. The aforementioned integrated modules may be implemented in either hardware or software functional modules.

[0343] It is understood that the processor in the embodiments of the present application may be a central processing unit (CPU), or may be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field programmable gate arrays (FPGA), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. The general-purpose processor may be a microprocessor or any conventional processor.

[0344] An embodiment of the present application further provides a computer-readable storage medium, in which a computer program or instruction is stored. When the computer program or instruction is executed, the method in the above embodiment is implemented.

[0345] An embodiment of the present application further provides a computer program product comprising instructions, which, when executed on a computer, enables the computer to execute the method in the above embodiment.

[0346] An embodiment of the present application also provides a communication system, including the above-mentioned communication device.

[0347] An embodiment of the present application also provides a communication system, which includes a first communication device, a second communication device, and a third communication device. The first communication device is used to execute the steps or methods executed by the first network element (or AMF) in the method in the above embodiment, the second communication device is used to execute the steps or methods executed by the second network element (or SMF) in the method in the above embodiment, and the third communication device is used to execute the steps or methods executed by the third network element (or UPF) in the method in the above embodiment.

[0348] The present application also provides a circuit, which is coupled to a memory and is used to execute the method shown in the above embodiment. The circuit may include a chip circuit.

[0349] An embodiment of the present application also provides a chip device, including a processor, for calling a computer program or computer instruction stored in the memory so that the processor executes the method provided in any one of the embodiments shown in Figure 3 or Figures 6 to 11 above.

[0350] In one possible implementation, the input of the chip device corresponds to the receiving operation in any one of the embodiments shown in FIG. 3 or FIG. 6 to FIG. 11 above, and the output of the chip device corresponds to the sending operation in any one of the embodiments shown in FIG. 3 or FIG. 6 to FIG. 11 above.

[0351] Optionally, the processor is coupled to the memory via an interface.

[0352] Optionally, the chip device further includes a memory, in which computer programs or computer instructions are stored.

[0353] When the above-mentioned communication device is a module applied to a network device, the network device module implements the functions of the network device in the above-mentioned method embodiment. The network device module receives information from other modules in the network device (such as a radio frequency module or an antenna), and the information is sent by the terminal device to the network device; or, the network device module sends information to other modules in the network device (such as a radio frequency module or an antenna), and the information is sent by the network device to the terminal device. The network device module here can be a baseband chip of the network device, or a CU, DU or other module, or a device under the O-RAN architecture, such as an open CU, open DU and other devices.

[0354] It should be noted that the above units or one or more of the units can be implemented by software, hardware, or a combination of the two. When any of the above units or units is implemented by software, the software exists in the form of computer program instructions and is stored in a memory, and a processor can be used to execute the program instructions and implement the above method flow.

[0355] In this application, a processor may be a general-purpose processor, a digital signal processor, an application-specific integrated circuit, a field-programmable gate array or other programmable logic device, a discrete gate or transistor logic device, or a discrete hardware component, and may implement or execute the methods, steps, and logic block diagrams disclosed in this application. A general-purpose processor may be a microprocessor or any conventional processor. The steps of the methods disclosed in this application may be directly executed by a hardware processor, or by a combination of hardware and software modules within the processor.

[0356] When the above units or units are implemented in hardware, the hardware can be any one or any combination of a CPU, a microprocessor, a digital signal processing (DSP) chip, a microcontroller unit (MCU), an artificial intelligence processor, an ASIC, a SoC, an FPGA, a PLD, a dedicated digital circuit, a hardware accelerator or a non-integrated discrete device, which can run the necessary software or not rely on the software to execute the above method flow.

[0357] Optionally, an embodiment of the present application further provides a chip system, comprising: at least one processor and an interface, wherein the at least one processor is coupled to a memory via the interface, and when the at least one processor executes a computer program or instruction in the memory, the chip system executes the method in any of the above method embodiments. Optionally, the chip system may be composed of a chip, or may include a chip and other discrete devices, which is not limited in the embodiments of the present application.

[0358] The memory in the present application may also be a circuit or any other device capable of implementing a storage function for storing program instructions and / or data. A memory is any other medium that can be used to carry or store a desired program code in the form of an instruction or data structure and can be accessed by a computer, but is not limited thereto. For example, the memory may be a non-volatile memory, such as a digital versatile disc (DVD), a hard disk drive (HDD), or a solid-state drive (SSD), or a volatile memory, such as a random-access memory (RAM).

[0359] It is understood that, in this application, "indication" can include direct indication, indirect indication, explicit indication, and implicit indication. When describing a certain indication information as indicating A, it can be understood that the indication information carries A, directly indicates A, or indirectly indicates A. In this application, the information indicated by the indication information is referred to as the information to be indicated. During implementation, there are many ways to indicate the information to be indicated. For example, but not limited to, the information to be indicated can be directly indicated, such as the information to be indicated itself or an index of the information to be indicated, or it can be indirectly indicated by indicating other information, where the other information is associated with the information to be indicated. It is also possible to indicate only a portion of the information to be indicated, while the rest of the information to be indicated is known or agreed upon in advance. For example, it is also possible to indicate specific information by using a pre-agreed (e.g., protocol-specified) order of arrangement of various information, thereby reducing the indication overhead to a certain extent. The information to be indicated can be sent as a whole or divided into multiple sub-information and sent separately, and the sending period and / or sending timing of these sub-information can be the same or different. This application does not limit the detailed sending method. The sending period and / or sending timing of these sub-information may be predefined, for example, predefined according to a protocol, or may be configured by the transmitting end device by sending configuration information to the receiving end device.

[0360] The at least one (item) involved in this application indicates one (item) or more (items). More than one (item) refers to two (items) or more than two (items). "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. In addition, it should be understood that although the terms first, second, etc. may be used to describe each object in this application, these objects should not be limited to these terms. These terms are only used to distinguish each object from each other.

[0361] The terms "including" and "having" mentioned above and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include other steps or units that are not listed, or may optionally include other steps or units that are inherent to these processes, methods, products or devices. It should be noted that, in this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or explanations. Any method or design described in this application as "exemplary" or "for example" should not be interpreted as being more preferred or more advantageous than other methods or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a more detailed manner.

[0362] A network element in a communication system can send a signal to another network element or receive a signal from another network element. The signal may include information, signaling, or data, etc. The network element can also be replaced by an entity, a network entity, a device, a terminal device, a communication module, a node, a communication node, etc. The present application uses the network element as an example for description. For example, the communication system may include at least one terminal device and at least one network device. The network device can send a downlink signal to the terminal device, and / or the terminal device can send an uplink signal to the network device. In addition, it can be understood that if the communication system includes multiple terminal devices, the multiple terminal devices can also send signals to each other, that is, the signal sending network element and the signal receiving network element can both be terminal devices.

[0363] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented using a software program, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the process or function described in the embodiment of the present application is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions can be transmitted from one website, computer, server or data center to another website, computer, server or data center via wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means.

[0364] Although the present application is described herein in conjunction with various embodiments, in the process of implementing the claimed application, those skilled in the art can understand and implement other changes to the disclosed embodiments by reviewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude multiple situations. A single processor or other unit can implement several functions listed in the claims. Certain measures are recorded in different dependent claims, but this does not mean that these measures cannot be combined to produce good results.

[0365] It is understood that the various numbers used in the embodiments of this application are merely for ease of description and are not intended to limit the scope of the embodiments of this application. The order of the sequence numbers of the above-mentioned processes does not necessarily imply a specific order of execution; the order of execution of the processes should be determined by their functions and inherent logic.

[0366] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0367] The components in the device of the embodiment of the present application can be merged, divided, or deleted according to actual needs. Those skilled in the art can combine or combine the different embodiments and features of the different embodiments described in this specification.

[0368] In this application, under the premise of no logical contradiction, the examples can reference each other, for example, the methods and / or terms between method embodiments can reference each other, for example, the functions and / or terms between device embodiments can reference each other, for example, the functions and / or terms between device examples and method examples can reference each other.

Claims

1. A communication method, characterized in that: The method comprises: receiving first indication information, where the first indication information is used to store downlink data sent to a terminal, where the terminal is in a radio resource control (RRC) inactive state; receiving downlink data sent to the terminal; storing the downlink data based on the first indication information; After the terminal enters the connected state, the stored downlink data is sent to the terminal.

2. The method according to claim 1, characterized in that After the terminal enters the connected state, sending the stored downlink data to the terminal includes: After the paging result of the first access network device to the terminal is a paging failure and the terminal enters a connected state, the stored downlink data is sent to the terminal, and the first access network device is the access network device that last served the terminal.

3. The method according to claim 1 or 2, characterized in that The storing the downlink data based on the first indication information includes: In a case where a paging result of the first access network device paging the terminal is a paging failure, the downlink data is stored based on the first indication information, and the first access network device is the access network device that last served the terminal.

4. The method according to any one of claims 1 to 3, characterized in that The first indication information indicates the storage of downlink data sent to the terminal, or indicates that the terminal is in an RRC inactive state, or indicates that the paging result of the first access network device paging the terminal is a paging failure, and the first access network device is the access network device that last served the terminal.

5. The method according to any one of claims 1 to 4, characterized in that The receiving first indication information includes: In a session establishment process or a session modification process of the terminal, the first indication information is received.

6. The method according to any one of claims 1 to 5, characterized in that The downlink data is voice service data.

7. The method according to any one of claims 1 to 6, characterized in that The method further comprises: After the terminal enters the connected state, receiving second indication information, the second indication information being used to delete the downlink data after sending the downlink data to the terminal, and / or being used to no longer store the downlink data sent to the terminal; Based on the second indication information, the downlink data is deleted after the downlink data is sent to the terminal, and / or it is determined that the downlink data sent to the terminal is no longer stored.

8. The method according to claim 7, characterized in that The second indication information indicates one or more of deleting the downlink data after sending the downlink data to the terminal, no longer storing the downlink data sent to the terminal, or indicating that the terminal is in a connected state.

9. A communication method, characterized in that: The method comprises: Determining that the terminal is in a radio resource control (RRC) inactive state; Based on the terminal being in an RRC inactive state, first indication information is sent to a third network element, where the first indication information is used to store downlink data sent to the terminal.

10. The method according to claim 9, characterized in that The sending first indication information to the third network element based on the terminal being in the RRC inactive state includes: When a paging result of the first access network device paging the terminal is a paging failure, the first indication information is sent to the third network element, and the first access network device is the access network device that last served the terminal.

11. The method according to claim 9 or 10, characterized in that The first indication information indicates the storage of downlink data sent to the terminal, or indicates that the terminal is in an RRC inactive state, or indicates that the paging result of the first access network device paging the terminal is a paging failure, and the first access network device is the access network device that last served the terminal.

12. The method according to any one of claims 9 to 11, characterized in that: The sending first indication information to the third network element based on the terminal being in the RRC inactive state includes: In a session establishment process or a session modification process of the terminal, the first indication information is sent to the third network element based on that the terminal is in an RRC inactive state.

13. The method according to any one of claims 9 to 12, characterized in that: Determining that the terminal is in a radio resource control (RRC) inactive state includes: Sending a first subscription request to a first network element, where the first subscription request is used to request notification of the terminal entering an RRC inactive state; A first notification message is received from the first network element, where the first notification message is used to instruct the terminal to enter an RRC inactive state.

14. The method according to claim 13, characterized in that The first subscription request is further used to request notification of the terminal entering a connected state. The method further includes: receiving a second notification message from the first network element, where the second notification message is used to instruct the terminal to enter a connected state; Based on the second notification message, second indication information is sent to the third network element, where the second indication information is used to delete the downlink data after sending the downlink data to the terminal, and / or to no longer store the downlink data sent to the terminal.

15. The method according to claim 14, characterized in that The second indication information indicates one or more of: deleting the downlink data after sending the downlink data to the terminal, indicating no longer storing the downlink data sent to the terminal, or indicating that the terminal is in a connected state.

16. A communication method, characterized in that: The method comprises: receiving a first subscription request, where the first subscription request is used to request notification of a terminal entering a radio resource control (RRC) inactive state; In a case where the terminal enters the RRC inactive state, a first notification message is sent based on the first subscription request, where the first notification message is used to instruct the terminal to enter the RRC inactive state.

17. The method according to claim 16, characterized in that The first subscription request is further used to request notification of the terminal entering a connected state. The method further includes: In a case where the terminal enters the connected state, a second notification message is sent based on the first subscription request, where the second notification message is used to indicate that the terminal enters the connected state.

18. A communication method, characterized in that: The method comprises: receiving a second subscription request, where the second subscription request is used to request notification of receipt of downlink data sent to a terminal, where the terminal is in a radio resource control (RRC) inactive state; receiving downlink data sent to the terminal; Sending a third notification message based on the second subscription request, where the third notification message is used to indicate that downlink data sent to the terminal has been received; receiving third indication information, where the third indication information is used to store the downlink data; storing the downlink data based on the third indication information; After the terminal enters the connected state, the stored downlink data is sent to the terminal.

19. The method according to claim 18, characterized in that After the terminal enters the connected state, sending the stored downlink data to the terminal includes: After the paging result of the first access network device to the terminal is a paging failure and the terminal enters a connected state, the stored downlink data is sent to the terminal, and the first access network device is the access network device that last served the terminal.

20. The method according to claim 18 or 19, characterized in that The storing the downlink data based on the third indication information includes: In a case where a paging result of the first access network device paging the terminal is a paging failure, the downlink data is stored based on the third indication information, and the first access network device is the access network device that last served the terminal.

21. A communication method, characterized in that: The method comprises: Sending a second subscription request, where the second subscription request is used to request notification of receipt of downlink data sent to a terminal, where the terminal is in a radio resource control (RRC) inactive state; receiving a third notification message, where the third notification message is used to indicate that downlink data sent to the terminal has been received; Third indication information is sent in response to the third notification message, where the third indication information is used to store downlink data of the terminal.

22. The method according to claim 21, characterized in that The sending of the second subscription message includes: Based on the terminal being in an RRC inactive state, sending the second subscription request.

23. The method according to claim 21 or 22, characterized in that The sending of the third indication information includes: In a case where the paging result of the first access network device paging the terminal is a paging failure, the third indication information is sent in response to the third notification message.

24. A communication system, characterized in that: The system includes a first network element, a second network element, and a third network element, the third network element is used to implement the method according to any one of claims 1-8 and 18-20, the second network element is used to implement the method according to any one of claims 9-17 and 21-23, and the first network element is used to implement the method according to any one of claims 16-17 and 21-23.

25. A communication device, characterized in that: comprising a unit for implementing the method as claimed in any one of claims 1 to 8, or comprising a unit for implementing the method as claimed in any one of claims 9 to 15, or comprising a unit for implementing the method as claimed in any one of claims 16 to 17, or comprising a unit for implementing the method as claimed in any one of claims 18 to 20, or comprising a unit for implementing the method as claimed in any one of claims 21 to 23.

26. A communication device, characterized in that: It includes a processor and an interface circuit, wherein the interface circuit is used to receive signals from other communication devices outside the communication device and transmit them to the processor or send signals from the processor to other communication devices outside the communication device, and the processor is used to implement the method as described in any one of claims 1 to 23 through a logic circuit or executing code instructions.

27. The communication device according to claim 26, characterized in that The communication device is a chip.

28. A chip module, characterized in that: The method comprises a transceiver component and a chip, wherein the chip is used to execute the method according to any one of claims 1 to 23.

29. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the method according to any one of claims 1 to 23 is implemented.

30. A computer program product, characterized in that The computer program product comprises program instructions, and when the program instructions are executed, the method according to any one of claims 1 to 23 is implemented.

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