Communication method and apparatus

Abstract

The present application relates to the technical field of communications, and provides a communication method and apparatus. The method comprises: an access and mobility management network element may actively instruct a session management network element to report the data volume of service data, for example, a first data volume of service data cached by a network in an inactive state of a terminal, so that the access and mobility management network element can notify an access network device of the corresponding data volume, for example, a second data volume, so as to allow the access network device to perform more accurate MTSDT decision.

Description

Communication method and device

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on August 9, 2023, with application number 202311009009.4 and application name “Communication Method and Device,” the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of communications, and in particular to a communication method and device. Background Art

[0003] When the radio resource control (RRC) is inactive, the terminal can enable the small data transmission (SDT) mechanism, such as mobile terminated (MT), i.e. downlink MT SDT. This mechanism can transmit small amounts of data without restoring the original data radio bearer (DRB) / signaling radio bearer (SRB), thereby reducing complexity and energy consumption on the terminal side.

[0004] For example, when downlink data arrives, the user plane function (UPF) network element reports a downlink data notification (DDN) message to the session management function (SMF) network element. The SMF network element then initiates a Namf service to the access and mobility management function (AMF) network element to determine whether the current UE is reachable. Subsequently, when the terminal is about to be reachable, the AMF network element notifies the radio access network (RAN) equipment of the arrival of downlink data to assist the RAN equipment in making MT SDT decisions.

[0005] However, how to ensure the accuracy of MT SDT judgment is a hot topic in current research.

[0006] Summary of the Invention

[0007] The embodiments of the present application provide a communication method and apparatus to ensure the accuracy of MT SDT judgment.

[0008] To achieve the above objectives, this application adopts the following technical solutions:

[0009] In a first aspect, a communication method is provided, comprising: an access and mobility management network element sending first information to a session management network element, and receiving a first data volume from the session management network element. The first information is used to trigger the session management network element to report the volume of cached service data of a terminal, where the cached service data of the terminal is service data cached by the network when the terminal is in an inactive state, and the first data volume is the volume of the cached service data of the terminal. Based on the first data volume, the access and mobility management network element sends a second data volume to an access network device of the terminal.

[0010] From this, it can be seen that the access and mobility management network element can actively instruct the session management network element to report the data volume of service data, such as the first data volume of service data cached by the network when the terminal is in an inactive state, so that the access and mobility management network element can inform the access network device of the corresponding data volume, such as the second data volume, so that the access network device can make a more accurate MT SDT judgment.

[0011] In one possible design, the access and mobility management network element sends first information to the session management network element, including: when the terminal state changes to a reachable state, the access and mobility management network element sends the first information to the session management network element, for the session management network element to report the amount of service data cached by the network during the entire unreachable state of the terminal, thereby improving the accuracy of the MT SDT judgment. The terminal state changing to a reachable state can be understood as the terminal device being about to be reachable or before the access and mobility management network element triggers the access network device to perform paging.

[0012] Optionally, the method described in the first aspect may further include: the access and mobility management network element determines that the state of the terminal is changed to a reachable state. It can be understood that compared with other devices / network elements informing the access and mobility management network element of the state change of the terminal, the access and mobility management network element determines the state change of the terminal on its own, which can avoid the delay and overhead generated by communication. For example, the access and mobility management network element determines that the state of the terminal is changed to a reachable state or is about to be changed to a reachable state based on the eDRX parameters of the terminal device, such as the eDRX cycle and the paging time window (PTW).

[0013] Optionally, the first information is carried in a session context request message, and the first data volume is carried in a session context response message, that is, the existing message implementation is reused to reduce the implementation complexity of the solution, or it can also be carried in a new message to achieve decoupling from the existing message and more flexible information element transmission.

[0014] In one possible design, the first information includes first indication information, and the first indication information is used to instruct the session management network element to report the amount of cached service data of the terminal when the first timer expires. For example, when the first timer expires when the terminal state changes to a reachable state, the session management network element reports the amount of service data cached by the network when the terminal is unreachable, thereby improving the accuracy of the MT SDT determination.

[0015] Optionally, the method described in the first aspect may further include: the access and mobility management network element determines the duration of the first timer based on the discontinuous reception parameters of the terminal, and sends the duration of the first timer to the session management network element. The discontinuous reception parameters of the terminal can be used to indicate the eDRX cycle and / or PTW of the terminal, that is, the time during which the terminal is in the awake state (or reachable state) in the inactive state, and the time during which it is in the dormant state (or unreachable state). In this way, the access and mobility management network element can determine the duration of the first timer based on the time when the terminal's state changes to the reachable state, and ensure that the first timer times out when the terminal's state changes to the reachable state or when the terminal's state is about to change to the reachable state.

[0016] Optionally, the first information may further include the duration of the first timer, that is, carried in the same information as the first indication information to reduce the number of communications. Of course, the duration of the first timer and the first indication information may also be carried in different information to achieve decoupling and more flexible cell transmission.

[0017] In one possible design, the first information may include second indication information, where the second indication information is used to instruct the session management network element to report the amount of cached service data of the terminal when the amount of cached service data of the terminal reaches a cached data amount threshold. For example, the data amount threshold may be the threshold value of the amount of data that can be carried by the SDT DRB of the access network device. That is, if the amount of cached service data of the terminal does not reach the cached data amount threshold, the access network device may perform MT SDT even if the session management network element does not report. However, if the amount of cached service data of the terminal reaches the cached data amount threshold, the session management network element reports it in a timely manner so that the access network device can promptly restore the terminal to a connected state for data transmission, thereby reducing transmission delay. Specifically, the second indication information may be used to instruct the session management network element to report the amount of service data in one or more QoS flows of the terminal when the amount of service data in one or more QoS flows of the terminal reaches the cached data amount threshold.

[0018] Optionally, the first information also includes a buffered data volume threshold, that is, carried in the same information as the second indication information to reduce communication times. Of course, the buffered data volume threshold and the second indication information can also be carried in different information to achieve decoupling and more flexible cell transmission.

[0019] Optionally, the first information is carried in a protocol data unit PDU session context update message, or the first information is carried in a mobile terminal termination MT response message, that is, the existing message implementation is reused to reduce the implementation complexity of the solution, or it can also be carried in a new message to achieve decoupling from the existing message and more flexible cell transmission.

[0020] In one possible design, the first information includes third indication information, and the third indication information is used to instruct the session management network element to report the amount of service data of the terminal each time the network receives service data of the terminal while the terminal is in an inactive and unreachable state. In this way, the session management network element can report the amount of service data cached by the network during the entire unreachable state of the terminal, thereby improving the accuracy of the MT SDT determination.

[0021] Optionally, the first information is carried in the MT response message, and the first data volume is carried in the MT request message, that is, the existing message implementation is reused to reduce the implementation complexity of the solution, or it can also be carried in a new message to achieve decoupling from the existing message and more flexible information element transmission.

[0022] In a possible design scheme, the first information also includes an identifier of the first quality of service QoS flow of the terminal. The first QoS flow can be one or more. The identifier of the first QoS flow can be used to indicate that the cached service data of the terminal is the data corresponding to the first QoS flow, that is, to instruct the session management network element to report the data volume corresponding to the first QoS flow. The first QoS flow supports SDT DRB small data transmission data bearer. That is to say, the access and mobility management network element can instruct the session management network element to only report the data volume corresponding to the specified QoS flow (such as the first QoS flow that supports SDT DRB) to avoid communication redundancy. Alternatively, if the first information does not include the identifier of the first QoS flow, the session management network element reports the data volume corresponding to all QoS flows under the terminal's session, such as reporting the data volume corresponding to each QoS flow at the granularity of the QoS flow.

[0023] Optionally, the method described in the first aspect may further include: the access and mobility management network element receives second information from the access network device of the terminal. The second information may include information about the first QoS flow. The access and mobility management network element sends the first information to the session management network element, including: the access and mobility management network element sends the first information to the session management network element based on the information about the first QoS flow. That is to say, the access network device can selectively let the core network report the data volume of the corresponding QoS flow according to the requirements of MT SDT to avoid communication redundancy. Alternatively, when the access and mobility management network element finds that other QoS flows other than the first QoS flow of the terminal have cached service data, it will not send the cached service data volume corresponding to the first QoS flow to the access network device.

[0024] Optionally, the second information may further include SDT enabling information. The SDT enabling information may be used to indicate the amount of cached service data of the terminal reported by the access and mobility management network element. For example, the information element of the SDT enabling information may indicate that the terminal currently in an inactive state is configured with an SDT DRB, thereby implicitly indicating the amount of cached service data of the terminal reported by the access and mobility management network element by indicating the configuration of the SDT DRB. Alternatively, the information element of the SDT enabling information may also indicate the amount of cached service data of the terminal reported by the access and mobility management network element.

[0025] Optionally, the second information further includes a data volume threshold for the SDT DRB, and the access and mobility management network element sends the first information to the session management network element, including: when the amount of data cached by the network is less than the data volume threshold for the SDT DRB, the access and mobility management network element sends the first information to the session management network element. The data cached by the network is data corresponding to the first QoS flow. In other words, when the amount of data cached by the network is less than the upper limit of the data volume that the SDT DRB can carry, the access and mobility management network element allows the network to continue caching and reporting the data volume; otherwise, the amount of data cached by the network is not sent to the access network device.

[0026] In one possible design, the first data volume includes the data volume corresponding to at least one QoS flow of the terminal, and the second data volume is the data volume corresponding to a QoS flow that supports SDT DRB among the at least one QoS flow. It will be understood that for QoS flows that do not support SDT DRB, even if the network caches the corresponding data, the access network device cannot transmit this data via MT SDT. In this case, the access and mobility management network element may filter the data volume to be reported and only provide the data volume corresponding to QoS flows that support SDT DRB to avoid communication redundancy. Alternatively, if the first data volume includes the data volume corresponding to at least one QoS flow of the terminal, if the access network device considers not only the data volume corresponding to QoS flows that support SDT DRB but also the data volume corresponding to QoS flows that do not support SDT DRB when making an MT SDT decision, the access and mobility management network element may directly send the first data volume to the access network device, i.e., the first data volume is the same as the second data volume. Alternatively, if the first data volume is the data volume corresponding to a QoS flow that supports SDT DRB, the access and mobility management network element may also directly send the first data volume to the access network device, i.e., the first data volume is the same as the second data volume.

[0027] In one possible design, before the access and mobility management network element sends the first information to the session management network element, the method described in the first aspect may further include: the access and mobility management network element receives a mobile terminal termination MT request message from the session management network element. The MT request message includes a third data volume, which is the data volume of the terminal's cached service data. When the terminal is in an inactive and unreachable state, the access and mobility management network element sends an MT response message to the session management network element based on the MT request message. The MT response message is used to indicate that the terminal is unreachable. That is, the access and mobility management network element can instruct the session management network element to subsequently report the data volume of the terminal's cached service data when the terminal's service data first arrives at the network, so as to avoid communication redundancy, such as instructing the session management network element when no service data arrives at the network, resulting in invalid reporting.

[0028] According to a second aspect, a communication method is provided, comprising: a session management network element receiving first information from an access and mobility management network element, and sending a first data volume to the access and mobility management network element based on the first information. The first information is used to trigger the session management network element to report the volume of cached service data of a terminal, where the cached service data of the terminal is service data cached by the network when the terminal is in an inactive state, and the first data volume is the volume of the cached service data of the terminal.

[0029] In one possible design, the first information is carried in a session context request message, and the first data volume is carried in a session context response message.

[0030] Optionally, the first information includes first indication information, and the first indication information is used to instruct the session management network element to report the data volume of the terminal's service data when the first timer expires. Accordingly, the session management network element sends the first data volume to the access and mobility management network element based on the first information, including: when the first timer expires, the session management network element sends the first data volume to the access and mobility management network element.

[0031] Optionally, the method described in the second aspect may further include: the session management network element starting the first timer when receiving the duration of the first timer from the access and mobility management network element.

[0032] Optionally, the first information further includes the duration of the first timer.

[0033] In one possible design, the first information includes second indication information, and the second indication information is used to instruct the session management network element to report the amount of cached service data of the terminal when the amount of cached service data of the terminal reaches a cached data amount threshold. Accordingly, the session management network element sends the first amount of data to the access and mobility management network element based on the first information, including: when the first amount of data reaches the cached data amount threshold, the session management network element sends the first amount of data to the access and mobility management network element.

[0034] Optionally, the first information also includes a cache data amount threshold.

[0035] Optionally, the first information is carried in a protocol data unit (PDU) session context update message, or the first information is carried in a mobile terminal terminated MT response message.

[0036] In one possible design, the first information includes third indication information, and the third indication information is used to instruct the session management network element to report the data volume of the terminal's service data each time the network receives service data from the terminal when the terminal is in an inactive and unreachable state. Accordingly, the session management network element sends a first data volume to the access and mobility management network element based on the first information, including: when the network receives cached service data from the terminal, the session management network element sends to the access and mobility management network element that the cached service data received from the terminal is the first data volume.

[0037] Optionally, the first information is carried in an MT response message, and the first data volume is carried in an MT request message.

[0038] In one possible design, the first information further includes an identifier of a first QoS flow of the terminal, where the identifier of the first QoS flow is used to indicate that the cached service data of the terminal is data corresponding to the first QoS flow. That is, the first data volume is the data volume of the data corresponding to the first QoS flow of the terminal.

[0039] Optionally, the first QoS flow supports SDT DRB small data transmission data bearer.

[0040] In one possible design scheme, the method described in the second aspect may also include: the session management network element obtains the first data volume locally from the session management network element based on the first information. Compared with obtaining the first data volume from other devices / network elements, the delay and overhead generated by communication can be avoided.

[0041] In one possible design, the network elements in the network include user-plane network elements. The method described in the second aspect may further include: the session management network element obtaining, from the user-plane network element based on the first information, a first data volume. For example, the session management network element may send third information to the user-plane network element based on the first information. The third information may be used to trigger the user-plane network element to report the amount of cached service data of the terminal. In this manner, the session management network element may receive the first data volume sent by the user-plane network element.

[0042] Optionally, if the first information includes the first indication information described above, the third information includes fourth indication information. The fourth indication information may be used to instruct the user plane network element to report the amount of cached service data of the terminal when a second timer expires, where the second timer is determined based on the first timer. In other words, the session management network element may send the fourth indication information to the user plane network element based on the first indication information.

[0043] Furthermore, the method described in the second aspect may also include: the session management network element sending the duration of the second timer to the user plane network element.

[0044] Furthermore, the third information also includes the duration of the second timer.

[0045] Optionally, if the first information includes the second indication information, the third information includes fifth indication information. The fifth indication information is used to instruct the user plane network element to report the amount of cached service data of the terminal when the amount of cached service data of the terminal reaches a cached data amount threshold. In other words, the session management network element may send the fifth indication information to the user plane network element based on the second indication information.

[0046] Furthermore, the third information may also include a cache data amount threshold.

[0047] Optionally, if the first information includes the third indication information described above, the third information includes sixth indication information. The sixth indication information may be used to instruct the user plane network element to report the amount of service data of the terminal each time it receives service data from the terminal when the terminal is in an inactive and unreachable state. In other words, the session management network element may send the sixth indication information to the user plane network element based on the third indication information.

[0048] Optionally, the third information may further include an identifier of the first QoS flow of the terminal, and the identifier of the first QoS flow may be used to instruct the user plane network element to report the data volume corresponding to the first QoS flow. If the third information does not include the identifier of the first QoS flow, the user plane network element reports the data volume corresponding to all QoS flows under the terminal's session or the data volume corresponding to all QoS flows with cached data volume, such as reporting the data volume corresponding to each QoS flow at the granularity of the QoS flow.

[0049] Furthermore, the first QoS flow supports SDT DRB.

[0050] In addition, the technical effects of the method described in the second aspect can also refer to the technical effects of the method described in the first aspect, and will not be repeated here.

[0051] In a third aspect, a communication method is provided, comprising: an access and mobility management network element receiving signaling to be sent to a terminal in an unreachable state (e.g., the terminal may be in an unreachable state while inactive); and the access and mobility management network element sending signaling-related information to an access network device of the terminal. The signaling-related information is used by the access network device to determine whether a small data transmission (SDT) is used to transmit signaling. For example, the signaling-related information includes the signaling data volume.

[0052] It can be seen that when the access and mobility management network element receives signaling to be sent to a terminal in an unreachable state, it can inform the access network device of the relevant information of the signaling (such as data volume) so that the access network device can make a more accurate MT SDT decision.

[0053] In one possible design, the access and mobility management network element sends signaling-related information to the access network device of the terminal. This includes: when the terminal's status changes to a reachable state, the access and mobility management network element sends signaling-related information to the access network device. That is, the access and mobility management network element can send the entire amount of signaling data to be sent to the terminal by the network during the entire period of the terminal's unreachable state to the access network device, thereby improving the accuracy of the MT SDT judgment. The terminal's status changing to a reachable state can be understood as meaning that the terminal device is about to be reachable or before the access and mobility management network element triggers the access network device to perform paging.

[0054] In a fourth aspect, a communication device is provided. The communication device includes: a module for executing the method described in any one of aspects 1 to 3, such as a transceiver module and a processing module. For example, the transceiver module is configured to indicate the transceiver function of the communication device, and the processing module is configured to perform functions of the communication device other than the transceiver function.

[0055] Optionally, the transceiver module may include a sending module and a receiving module, wherein the sending module is used to implement the sending function of the communication device described in the fourth aspect, and the receiving module is used to implement the receiving function of the communication device described in the fourth aspect.

[0056] Optionally, the communication device described in the fourth aspect may further include a storage module, wherein the storage module stores a program or instruction. When the processing module executes the program or instruction, the communication device can execute the method described in any one of the first to third aspects.

[0057] It can be understood that the communication device described in the fourth aspect can be a network device, or a chip (system) or other parts or components that can be set in the network device, or a device that includes a network device. This application does not limit this.

[0058] In addition, the technical effects of the communication device described in the fourth aspect can refer to the technical effects of the methods described in any one of the first to third aspects, and will not be repeated here.

[0059] In a fifth aspect, a communication device is provided. The communication device includes: a module for executing the method described in any one of aspects 1 to 3, such as a transceiver module and a processing module. For example, the transceiver module is configured to indicate the transceiver function of the communication device, and the processing module is configured to perform functions of the communication device other than the transceiver function.

[0060] Optionally, the transceiver module may include a sending module and a receiving module, wherein the sending module is used to implement the sending function of the communication device described in the fifth aspect, and the receiving module is used to implement the receiving function of the communication device described in the fifth aspect.

[0061] Optionally, the communication device described in the fifth aspect may further include a storage module, wherein the storage module stores a program or instruction. When the processing module executes the program or instruction, the communication device can execute the method described in any one of the first to third aspects.

[0062] It can be understood that the communication device described in the sixth aspect can be a network device, or a chip (system) or other parts or components that can be set in the network device, or a device that includes a network device. This application does not limit this.

[0063] In addition, the technical effects of the communication device described in the fifth aspect can refer to the technical effects of the methods described in any one of the first to third aspects, and will not be repeated here.

[0064] In a sixth aspect, a communication device is provided, comprising: a processor configured to execute the method described in any one of the first to third aspects.

[0065] In one possible design solution, the communication device described in the sixth aspect may further include a transceiver. The transceiver may be a transceiver circuit or an interface circuit. The transceiver may be used for the communication device described in the sixth aspect to communicate with other communication devices.

[0066] In one possible design, the communication device described in aspect 6 may further include a memory. The memory may be integrated with the processor or provided separately. The memory may be used to store the computer program and / or data involved in the method described in any one of aspects 1 to 3.

[0067] In an embodiment of the present application, the communication device described in the sixth aspect can be the network device described in any one of the first to third aspects, or a chip (system) or other parts or components that can be set in the network device, or a device that includes the network device.

[0068] In addition, the technical effects of the communication device described in the sixth aspect can refer to the technical effects of the methods described in any one of the first to third aspects, and will not be repeated here.

[0069] In a seventh aspect, a communication device is provided, comprising: a processor coupled to a memory, the processor configured to execute a computer program stored in the memory, so that the communication device performs the method described in any one of the first to third aspects.

[0070] In one possible design solution, the communication device described in the seventh aspect may further include a transceiver. The transceiver may be a transceiver circuit or an interface circuit. The transceiver may be used for the communication device described in the seventh aspect to communicate with other communication devices.

[0071] In an embodiment of the present application, the communication device described in the seventh aspect can be the network device described in any one of the first to third aspects, or a chip (system) or other parts or components that can be set in the network device, or a device that includes the network device.

[0072] In addition, the technical effects of the communication device described in the seventh aspect can refer to the technical effects of the methods described in any one of the first to third aspects, and will not be repeated here.

[0073] In an eighth aspect, a communication device is provided, comprising: a processor and a memory; the memory is used to store a computer program, and when the processor executes the computer program, the communication device executes the method described in any one of the first to third aspects.

[0074] In one possible design solution, the communication device described in the eighth aspect may further include a transceiver. The transceiver may be a transceiver circuit or an interface circuit. The transceiver may be used for the communication device described in the eighth aspect to communicate with other communication devices.

[0075] In an embodiment of the present application, the communication device described in aspect 8 may be the network device described in any one of aspects 1 to 3, or a chip (system) or other parts or components that may be set in the network device, or a device that includes the network device.

[0076] In addition, the technical effects of the communication device described in the eighth aspect can refer to the technical effects of the methods described in any one of the first to third aspects, and will not be repeated here.

[0077] In a ninth aspect, a communication system is provided, which includes at least two devices according to the first to third aspects.

[0078] In a tenth aspect, a computer-readable storage medium is provided, comprising: a computer program or instructions; when the computer program or instructions are run on a computer, the computer is caused to execute the method described in any one of the first to third aspects.

[0079] In an eleventh aspect, a computer program product is provided, comprising a computer program or instructions, which, when executed on a computer, causes the computer to execute the method described in any one of the first to third aspects. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] FIG1 is a schematic diagram of the architecture of a 5G mobile communication system;

[0081] FIG2 is a schematic diagram of the architecture of a communication system provided in an embodiment of the present application;

[0082] FIG3 is a flow chart of a communication method according to an embodiment of the present application;

[0083] FIG4 is a second flow chart of the communication method provided in an embodiment of the present application;

[0084] FIG5 is a third flow chart of the communication method provided in an embodiment of the present application;

[0085] FIG6 is a fourth flow chart of a communication method according to an embodiment of the present application;

[0086] FIG7 is a fifth flow chart of a communication method according to an embodiment of the present application;

[0087] FIG8 is a sixth flow chart of a communication method according to an embodiment of the present application;

[0088] FIG9 is a first structural diagram of a communication device provided in an embodiment of the present application;

[0089] FIG10 is a second structural diagram of the communication device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0090] For ease of understanding, the technical terms and application architecture involved in the embodiments of this application are first introduced below.

[0091] 1. Fifth generation (5G) mobile communication system (abbreviated as 5G system (5G system, 5GS)):

[0092] Figure 1 is a schematic diagram of the 5GS architecture. As shown in Figure 1, the 5GS includes an access network (AN) and a core network (CN), and may also include terminals.

[0093] The terminal may be one or more, such as a first terminal, a second terminal, a third terminal, etc. A terminal may be a terminal with transceiver functions, or may be a chip or chip system provided in the terminal. The terminal may also be referred to as user equipment (UE), access terminal, subscriber unit (subscriber unit), user station, mobile station (MS), mobile station, remote station, remote terminal, mobile device, user terminal, terminal, wireless communication device, user agent, or user device. The terminal in the embodiments of the present application can be a mobile phone, a cellular phone, a smart phone, a tablet computer, a wireless data card, a personal digital assistant (PDA), a wireless modem, a handheld device (handset), a laptop computer, a machine type communication (MTC) terminal, a computer with wireless transceiver function, a virtual reality (VR) terminal, an augmented reality (AR) terminal, a smart home device (for example, a refrigerator, a television, an air conditioner, an electric meter, etc.), an intelligent robot, a robotic arm, a workshop equipment, 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, a vehicle-mounted terminal, a roadside unit with terminal function, or a wireless terminal in a smart city. The terminal device of the present application may also be an onboard module, onboard module, onboard component, onboard chip or onboard unit built into a vehicle as one or more components or units. The terminal device may also be other devices with terminal functions, for example, the terminal device may also be a device that functions as a terminal in D2D communication.

[0094] The embodiments of this application do not limit the device form factor of the terminal. The device used to implement the functions of the terminal device can be the terminal device; it can also be a device that supports the terminal device to implement the functions, such as a chip system. The device can be installed in the terminal device or used in conjunction with the terminal device. In the embodiments of this application, the chip system can be composed of chips or include chips and other discrete devices.

[0095] The above-mentioned AN is used to implement access-related functions, and can provide network access functions for authorized users in a specific area. It can also determine transmission links of different qualities to transmit user data based on the user level, service requirements, etc. AN forwards control signals and user data between the terminal and the CN. The AN may include: access network equipment, also known as RAN equipment. The CN is mainly responsible for maintaining the subscription data of the mobile network and providing functions such as session management, mobility management, policy management, and security authentication for the terminal. The CN mainly includes the following network elements: UPF network element, authentication service function (AUSF) network element, AMF network element, SMF network element, network slice selection function (NSSF) network element, network exposure function (NEF) network element, network function repository function (NRF) network element, policy control function (PCF) network element, unified data management (UDM) network element, unified data repository (UDR), and application function (AF).

[0096] RAN equipment, that is, access network devices can be one or more. The access network device can be a device with wireless transceiver functions, or it can be a chip or chip system provided on the device, located in the access network (AN) of the communication system, to provide access services for the terminal. For example, the access network device can be called a radio access network device (RAN) device, which can specifically be a next-generation mobile communication system, such as a 6G access network device, such as a 6G base station, or in the next-generation mobile communication system, the access network device can also have other naming methods, which are all covered within the scope of protection of the embodiments of this application, and this application does not impose any limitations on this. Alternatively, the access network device may include 5G, such as a gNB in ​​a new radio (NR) system, or one or a group of antenna panels (including multiple antenna panels) of a base station in 5G, or a network node constituting a gNB, a transmission and reception point (TRP or TP), or a transmission measurement function (TMF), such as a central unit (CU), a distributed unit (DU), a CU-control plane (CP), a CU-user plane (UP), a radio unit (RU), an RSU with base station functions, a wired access gateway, or a 5G core network element. Alternatively, the access network device may include an access point (AP) in a wireless fidelity (WiFi) system, a wireless relay node, a wireless backhaul node, various types of macro base stations, micro base stations (also known as small cells), relay stations, access points, wearable devices, vehicle-mounted devices, and the like.

[0097] Among them, the CU and DU can be set separately, or can also be included in the same network element, such as a baseband unit (BBU). The RU can be included in a radio frequency device or a radio frequency unit, such as a remote radio unit (RRU), an active antenna unit (AAU) or a remote radio head (RRH). It can be understood that the network device can be a CU node, a DU node, or a device including a CU node and a DU node. In addition, the CU can be divided into a network device in the access network RAN, or the CU can be divided into a network device in the core network CN, and there is no limitation here.

[0098] In different systems, CU (or CU-CP and CU-UP), DU or RU may also have different names, but those skilled in the art can understand their meanings. For example, in the ORAN system, CU may also be called O-CU (Open CU), DU may also be called O-DU, CU-CP may also be called O-CU-CP, CU-UP may also be called O-CU-UP, and RU may also be called O-RU. For the convenience of description, this application uses CU, CU-CP, CU-UP, DU and RU as examples for description. Any unit of CU (or CU-CP, CU-UP), DU and RU in this application can be implemented by a software module, a hardware module, or a combination of a software module and a hardware module.

[0099] The UPF network element is mainly responsible for user data processing (forwarding, receiving, billing, etc.). For example, the UPF network element can receive user data from the data network (DN) and forward the user data to the terminal through the access network equipment. The UPF network element can also receive user data from the terminal through the access network equipment and forward the user data to the DN. The DN network element refers to the operator network that provides data transmission services to users. For example, the Internet Protocol (IP) Multimedia Service (IMS), the Internet, etc. The DN can be an operator's external network or a network controlled by the operator, which is used to provide business services to terminal devices.

[0100] The AUSF network element is mainly used to perform terminal security authentication.

[0101] The AMF network element is mainly used for mobility management in mobile networks, such as user location update, user network registration, and user handover.

[0102] The SMF network element is primarily used for session management in mobile networks, such as session establishment, modification, and release. Specific functions include allocating Internet Protocol (IP) addresses to users and selecting UPF network elements that provide packet forwarding capabilities.

[0103] The PCF network element mainly supports providing a unified policy framework to control network behavior, provides policy rules to the control layer network function, and is responsible for obtaining user subscription information related to policy decisions. The PCF network element can provide policies such as quality of service (QoS) policy and slice selection policy to the AMF network element and SMF network element.

[0104] The NSSF network element is mainly used to select network slices for terminals.

[0105] NEF network elements are mainly used to support the opening of capabilities and events.

[0106] UDM network elements are mainly used to store user data, such as subscription data, authentication / authorization data, etc.

[0107] The UDR network element is mainly used to store structured data, including contract data and policy data, externally exposed structured data, and application-related data.

[0108] AF mainly supports interaction with CN to provide services, such as influencing data routing decisions, policy control functions, or providing some third-party services to the network side.

[0109] 2. 5G Internet of Things (IoT) energy saving:

[0110] New Radio (NR) machine-type communications (MTC), such as massive machine-type communications (mMTC), is a key application scenario for 5G networks, primarily targeting various IoT applications based on cellular networks. Unlike low-power wide-area (LPWA) coverage, typical application scenarios for NR MTC include video surveillance (such as surveillance cameras), industrial sensor networks (such as temperature and pressure sensors), and wearable devices (such as smart bracelets, smart watches, and smart glasses). To support the low-power requirements of IoT devices, the 3rd Generation Partnership Project (3GPP) defined extended discontinuous reception (eDRX) in RRC inactivity (also known as long eDRX) in Release 18. This feature, with an eDRX cycle greater than 10.24 seconds, allows terminals to sleep for longer periods in RRC inactivity. This also creates new demands for the network (CN), which is why the standard introduces CN-assisted RAN equipment for downlink communication processing. For example, the CN can help buffer downlink data for terminals in long eDRX.

[0111] Specifically, when a terminal supporting REDCAP registers with the network side, the network may select an AMF network element that supports long-latency communication capabilities for the terminal based on local policy configuration. The long-latency communication capabilities may include: the ability to manage the reachability of terminals with long eDRX, and the ability to support the instructing caching of downlink data in the SMF network element / UPF network element when the terminal is unreachable. After configuring the long eDXR of the terminal, the RAN device can indicate to the AMF network element that the terminal has entered or is about to enter the deactivated state and is configured with long eDRX parameters, and send the eDRX parameters to the AMF network element. The AMF will then instruct the SMF / UPF network element to cache the downlink data of the terminal. In this way, when downlink data from a terminal arrives at the UPF network element, the SMF / UPF network element caches the corresponding downlink data. In addition, the UPF network element can also notify the SMF network element that downlink data from a terminal has arrived, and the SMF network element sends a terminal reachability query request to the AMF network element to trigger paging, enabling the terminal to restore network connection. The SMF network element can also indicate whether extended caching capability (long-term data caching capability) is supported. If the terminal is currently reachable, the AMF network element can trigger the RAN device to page the terminal, causing the terminal device to enter a connected state, thereby sending the terminal's downlink data to the terminal. However, if the terminal is currently unreachable, the AMF network element can inform the SMF network element of the maximum waiting time determined based on the eDRX parameters, and the SMF network element caches the terminal's downlink data based on the maximum waiting time. Subsequently, when the terminal is about to be reachable, the AMF network element can trigger the RAN device to page the terminal through an N2 message, enabling the terminal to restore to an RRC connected state, so that the previously cached downlink data can be sent to the terminal through the RAN device.

[0112] 3. SDT:

[0113] When RRC is inactive, RAN equipment can enable the SDT mechanism, enabling small data transmissions without restoring the original DRB / SRB, thereby reducing complexity and energy consumption on the terminal side. When the terminal restores the original DRB / SRB, it enters the connected state, meaning that the original DRB / SRB is the DRB / SRB used by the terminal in the connected state.

[0114] For example, when the terminal is released to the RRC inactive state (or inactive state), the RAN device can indicate to the terminal which DRB / SRB is the DRB / SRB for SDT, that is, SDT DRB / SRB, or, for each DRB / SRB configuration, whether it can use SDT for DRB / SRB recovery. When the terminal has uplink data or signaling to send, the terminal can decide whether to initiate mobile initiated (MO), that is, uplink, MO SDT, based on business requirements and whether the corresponding DRB / SRB is configured with SDT DRB / SRB. Of course, MO SDT can also consider data size or other information, which depends on the internal implementation of the terminal and is not restricted by the standard. If the UE decides not to trigger MO SDT transmission, the original regular DRB / SRB is restored. When there is downlink data, since the RRC inactive state is considered when the eDRX cycle is less than 10.24s, the core network will not assist the RAN device in processing downlink data or signaling, that is, the RAN device will receive downlink data from the UPF network element. The RAN device can decide whether to perform mobile terminated (MT) based on whether the DRB corresponding to the downlink data is configured with SDT and the specific data volume of the downlink data, that is, downlink MT SDT. Specifically, if the RAN device decides to perform MT SDT, then the RAN device will add MT SDT indication information to the paging message during downlink paging to trigger the terminal to restore the corresponding SDT DRB / SRB when restoring the connection.

[0115] After the introduction of long eDRX in R18, the terminal's downlink data or signaling will be processed by the CN. For details, please refer to the relevant introduction above. However, since the RAN equipment cannot perceive the DRB corresponding to the downlink data or the data size of the downlink data, the current standard already supports the introduction of the QoS flow identifier corresponding to the downlink data in the above-mentioned N2 message, such as the QoS flow ID, PDU session ID, and data volume, to assist the RAN equipment in determining the MT SDT. Specifically, when downlink data arrives, the UPF network element reports a DDN message to the SMF network element, and the SMF network element responds by sending a NAMF service message (for example, the MT Enable UE Reachability Request (Namf_MT_EnableUERechability request) message) to the AMF network element to query UE reachability or enable UE reachability. At this time, if the terminal is currently unreachable due to reasons such as the terminal entering eDRX sleep, the AMF network element rejects the SMF network element's NAMF service and instructs the SMF network element not to initiate the corresponding NAMF service. When the terminal's status is about to change to a reachable state, the AMF network element can trigger the RAN device to page the terminal, and at the same time inform the RAN device of the amount of cached downlink data corresponding to each QoS flow to assist the RAN device in making MT SDT decisions. Moreover, after the UE resumes the connection, whether it enters the connected state or is still in the inactive state for MO / MT SDT transmission, the AMF network element can also notify the SMF network element to cancel the cache or send the previously cached downlink data.

[0116] However, the time between a terminal's downlink data arriving at the UPF and the AMF determining the terminal's reachability and triggering the RAN to page the terminal can span the entire long eDRX cycle. During this time, the amount of downlink data cached by the SMF / UPF may change. Therefore, how the AMF can inform the RAN of the latest (or accurate) data volume remains an unresolved issue.

[0117] In response to the above technical problems, the embodiments of the present application propose the following technical solutions.

[0118] The technical solution in this application will be described below with reference to the accompanying drawings.

[0119] The technical solutions of the embodiments of the present application can be applied to various communication systems, such as wireless network systems, vehicle-to-everything (V2X) communication systems, device-to-device (D2D) communication systems, Internet of Vehicles communication systems, fourth-generation (4G) mobile communication systems, such as long-term evolution (LTE) systems, world-wide interoperability for microwave access (WiMAX) communication systems, 5G, such as NR systems, and future communication systems.

[0120] In the embodiment of the present application, "indication" may include direct indication and indirect indication, and may also include explicit indication and implicit indication. The information indicated by a certain information (such as the first indication information, the second indication information, or the third indication information below) is called information to be indicated. In the specific implementation process, there are many ways to indicate the information to be indicated, such as but not limited to, the information to be indicated can be directly indicated, such as the information to be indicated itself or the index of the information to be indicated. The information to be indicated can also be indirectly indicated by indicating other information, wherein the other information and the information to be indicated have an association relationship. It is also possible to indicate only a part of the information to be indicated, while the other parts of the information to be indicated are known or agreed in advance. For example, the indication of specific information can be achieved by means of the arrangement order of each information agreed in advance (such as specified in the protocol), thereby reducing the indication overhead to a certain extent. At the same time, the common parts of each information can be identified and indicated uniformly to reduce the indication overhead caused by indicating the same information separately.

[0121] In addition, the specific indication method can also be various existing indication methods, such as but not limited to the above-mentioned indication methods and various combinations thereof. The specific details of the various indication methods can be referred to the prior art and will not be repeated herein. As can be seen from the above, for example, when there are multiple information indicating the same type, there may be situations where the indication methods for different information are different. In the specific implementation process, the indication method can be selected according to specific needs. The embodiment of the present application does not limit the selected indication method. In this way, the indication method involved in the embodiment of the present application should be understood to cover various methods that can enable the party to be indicated to obtain the information to be indicated.

[0122] It should be understood that 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 time of these sub-information can be the same or different. The specific sending method is not limited in the embodiments of this application. The sending period and / or sending time of these sub-information can be predefined, for example, predefined according to a protocol, or can be configured by the transmitting device by sending configuration information to the receiving device.

[0123] "Pre-definition" or "pre-configuration" can be implemented by pre-saving corresponding codes, tables or other methods that can be used to indicate relevant information in the device, and the embodiments of the present application do not limit the specific implementation method. Among them, "saving" can mean saving in one or more memories. The one or more memories can be set separately or integrated in an encoder or decoder, a processor, or a communication device. The one or more memories can also be partially set separately and partially integrated in a decoder, a processor, or a communication device. The type of memory can be any form of storage medium, and the embodiments of the present application do not limit this.

[0124] The "protocol" involved in the embodiments of the present application may refer to a protocol family in the communication field, a standard protocol with a similar protocol family frame structure, or a related protocol used in future communication systems. The embodiments of the present application do not make specific limitations on this.

[0125] In the embodiments of the present application, descriptions such as "when...", "in the case of...", "if" and "if" all mean that the device will perform corresponding processing under certain objective circumstances. It does not limit the time, nor does it require the device to perform judgment actions when implemented, nor does it mean that there are other limitations.

[0126] In the description of the embodiments of the present application, unless otherwise specified, " / " indicates that the objects associated with each other are in an "or" relationship. For example, A / B can represent A or B. "And / or" in the embodiments of the present application is only a description of the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. In addition, in the description of the embodiments of the present application, unless otherwise specified, "multiple" refers to two or more than two. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can represent: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or multiple. In addition, in order to facilitate the clear description of the technical solutions of the embodiments of the present application, in the embodiments of the present application, words such as "first" and "second" are used to distinguish between identical or similar items with basically the same functions and effects. Those skilled in the art will understand that words such as "first" and "second" do not limit the quantity and execution order, and words such as "first" and "second" do not necessarily limit differences. At the same time, in the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or design. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a concrete way for easy understanding.

[0127] The network architecture and business scenarios described in the embodiments of the present application are intended to more clearly illustrate the technical solutions of the embodiments of the present application, and do not constitute a limitation on the technical solutions provided in the embodiments of the present application. A person skilled in the art will appreciate that, with the evolution of the network architecture and the emergence of new business scenarios, the technical solutions provided in the embodiments of the present application are equally applicable to similar technical problems.

[0128] To facilitate understanding of the embodiments of the present application, a communication system applicable to the embodiments of the present application is first described in detail using the communication system shown in Figure 2 as an example. For example, Figure 2 is a schematic diagram of the architecture of a communication system applicable to the communication method provided in the embodiments of the present application.

[0129] As shown in Figure 2, the communication system can be applied to the above-mentioned 5GS, and mainly includes: access and mobility management network elements and session management network elements.

[0130] The access and mobility management network element can be the AMF network element in the above-mentioned 5GS. For details, please refer to the above-mentioned relevant introduction, or it can be a network element used to implement the corresponding functions of access and mobility management in future communication systems. There is no limitation on this.

[0131] The session management network element can be the SMF network element in the above-mentioned 5GS, for details, please refer to the above-mentioned relevant introduction, or it can be a network element used to implement the corresponding function of session management in the future communication system, which is not limited to this.

[0132] In this communication system, the access and mobility management network element can proactively indicate the data volume of service data reported from the session management network element, such as the first data volume of service data cached by the network when the terminal is in an inactive state, so that the access and mobility management network element can accordingly inform the access network device of the corresponding data volume, such as the second data volume, so that the access network device can make a more accurate MT SDT judgment. And / or, when the access and mobility management network element receives signaling to be sent to a terminal in an unreachable state, it can also inform the access network device of relevant information (such as data volume) of the signaling, so that the access network device can make a more accurate MT SDT judgment. The following is a detailed introduction through the implementation of the method.

[0133] It is understood that the network referred to in the embodiments of the present application may be a network to which a terminal is registered or attached, such as an operator network, specifically a public land mobile network (PLMN), or may be a network of other types or standards, without limitation. The "network" mentioned below, unless otherwise specified, may be understood to mean a "network element / device / entity in the network," such as a session management network element, a user plane network element, an access network device, etc., without limitation.

[0134] The following will specifically describe the interaction process between each network element / device in the above communication system through a method embodiment in conjunction with Figures 3 to 8. The communication method provided in the embodiment of the present application can be applied to the above communication system and specifically applied to various scenarios mentioned in the above communication system, which will be described in detail below.

[0135] Figure 3 is a flow chart of a communication method according to an embodiment of the present application. The communication method is applicable to the above communication system and mainly involves the interaction between access and mobility management network elements, session management network elements, and user plane network elements.

[0136] As shown in Figure 3, the process of the communication method is as follows:

[0137] S301: An access and mobility management network element sends first information to a session management network element.

[0138] Correspondingly, the session management network element receives the first information from the access and mobility management network element.

[0139] The first information may be used to trigger / instruct / request the session management network element to report the amount of cached service data of the terminal. The cached service data of the terminal may be service data cached by the network when the terminal is in an inactive state. The service data may specifically be data corresponding to a first QoS flow of the terminal, or data to be carried by the first QoS flow.

[0140] Specifically, the first information may include an identifier of the first QoS flow, such as QFI. Further, the first information may be used to indicate the amount of data corresponding to the reported first QoS flow, or to indicate the amount of data corresponding to the first QoS flow cached in the reported network.

[0141] It should be noted that the data corresponding to the first QoS flow cached by the network mentioned above can be a network element in the network (such as the core network), such as a session management network element or a user plane network element, etc., which caches the data corresponding to the first QoS flow without restriction.

[0142] The first QoS flow may be one or more QoS flows of the terminal. The first QoS flow may be all or part of the QoS flows of the terminal. Specifically, the first QoS flow may be one or more PDU session bearers established by a session management network element, without limitation.

[0143] For example, assuming that all QoS flows of a terminal include QoS flows #1 to QoS flows #3, the first QoS flow may be all QoS flows of the terminal, including QoS flows #1 to QoS flows #3. Alternatively, the first QoS flow may be a portion of the QoS flows of the terminal. For example, the portion of QoS flows may be different types of QoS flows, specifically including QoS flows that support SDT DRBs and QoS flows that do not support SDT DRBs. A QoS flow that supports SDT DRBs may refer to a QoS flow whose corresponding DRB is configured with an SDT DRB, and the data carried by the QoS flow can be transmitted via SDT. A QoS flow that does not support SDT DRBs may refer to a QoS flow whose corresponding DRB is not configured with an SDT DRB, and the data carried by the QoS flow cannot be transmitted via SDT. For another example, the portion of QoS flows may also be QoS flows of a specified type, specifically including only QoS flows that support SDT DRBs. That is, the first QoS flow supports SDT DRBs. For example, if QoS flow #1 supports SDT DRBs, QoS flows #2 and QoS flows #3 do not support SDT DRBs, and the specified type is a QoS flow that supports SDT DRBs, then the first QoS flow only includes QoS flow #1.

[0144] It can be seen that the access and mobility management network element can send the first information, which is used to instruct the session management network element to report the amount of data corresponding to the specified type of QoS flow (such as the QoS flow supporting SDT DRB). Specifically, the first information can include the specified type, which can avoid communication redundancy.

[0145] It can be understood that when the first information does not include the identifier of the first QoS flow, the session management network element can report the data volume corresponding to all QoS flows of the terminal cached by the network by default, such as reporting the data volume corresponding to each QoS flow at the granularity of the QoS flow, or reporting the data volume corresponding to the QoS flows in which downlink data arrives or downlink data is cached among all QoS flows.

[0146] It should be pointed out that the session management network element can report the data volume of cached service data corresponding to which QoS flows of the terminal according to the protocol pre-definition, or it can negotiate in advance with the access and mobility management network element and / or the access network device to report the data volume of cached service data corresponding to which QoS flows of the terminal. Furthermore, after receiving the first information, the session management network element reports the data volume of these QoS flows by default.

[0147] The access and mobility management network element may trigger the session management network element to report the data volume by using the sending timing of the first information or the information contained in the first information, which will be introduced in different ways below.

[0148] Mode 1: When the state of the terminal changes to a reachable state, the access and mobility management network element sends first information to the session management network element.

[0149] For example, the access and mobility management network element may obtain the terminal's discontinuous reception parameters in advance from the access network device corresponding to the terminal (such as the access network device to which the terminal is currently connected). The discontinuous reception parameters may be used to indicate the terminal's eDRX cycle and paging time window (PTW), that is, the time during which the terminal is in an awake state (or a reachable state) and the time during which it is in a dormant state (or an unreachable state) in an inactive state. In this way, the access and mobility management network element may determine the transition of the terminal's state to a reachable state, or the timing at which the terminal's state transitions to a reachable state, and send first information to the session management network element when or before the timing is reached, such as sending a session context request message carrying the first information.

[0150] It should be pointed out that the first information can be carried in an existing message to reduce the implementation complexity of the solution, or it can be carried in a new message to achieve decoupling from the existing message and more flexible information element transmission.

[0151] It is understood that the terminal's state transition can also be notified to the access and mobility management network element by other devices, such as access network devices, without limitation. The terminal's state transition can be determined independently by the access and mobility management network element, thus avoiding the delay and overhead caused by notification by other network elements.

[0152] In addition, since the network can cache the service data received from the terminal after the terminal enters the unreachable state, when the access and mobility management network element triggers the reporting of the data volume of the cached service data when the terminal state changes to the reachable state or before, the session management network element can report the data volume of the service data cached by the network during the entire unreachable state of the terminal, which can improve the accuracy of the MT SDT judgment.

[0153] It is understood that, unless otherwise specified, the "access network device" mentioned in the embodiments of the present application refers to "the access network device corresponding to the terminal" or "the access network device currently accessed by the terminal". In addition, the "terminal state changes to a reachable state" referred to in the embodiments of the present application can be broadly understood, and can be understood as meaning that before the access and mobility management network element triggers the access network device to perform paging, the terminal state has changed to a reachable state, is about to change to a reachable state, or before changing to a reachable state, for example, 10 milliseconds (ms) or any possible duration in advance. That is, taking into account communication and processing delays, the session management network element is triggered in advance to report the data volume, so that when the access and mobility management network element sends the data volume to the access network device to perform MT SDT, the terminal is just in a reachable state (or is about to be in a reachable state), so as to fully utilize the duration of the reachable state for data transmission.

[0154] Mode 2: The first information includes first indication information, and the first indication information is used to instruct the session management network element to report the amount of buffered service data of the terminal when the first timer times out.

[0155] For example, the first timer may be a timer of a session management network element. The first timer may expire when the terminal state changes to a reachable state, so that the session management network element reports the amount of service data cached by the network during the entire unreachable state of the terminal, thereby improving the accuracy of the MT SDT judgment.

[0156] In mode 2, the access and mobility management network element may multiplex a session update message or an MT message to send the first information to the session management network element. For example, when the access network device notifies the access and mobility management network element that the terminal has been or will be released to the inactive state, the access and mobility management network element may send the first information to the session management network element through a session update message, such as a PDU session context update message, and instruct the session management network element to cache the downlink data of the terminal. For another example, the access and mobility management network element may send the first information to the session management network element through an MT message, such as an MT enable UE reachability response (Namf_MT_EnableUERechability response) message. Specifically, when the terminal is in the inactive state, if the service data of the terminal arrives at the user plane network element for the first time, the user plane network element may send a data arrival notification message to the session management network element to indicate that the service data of the terminal with the third data volume has arrived, thereby triggering the terminal to enter a reachable state. In this way, the session management network element may send an MT request message, such as an MT enable UE reachability request message, to the access and mobility management network element to trigger paging of the terminal, thereby restoring the terminal's connection with the network. Optionally, the message may also indicate that the terminal's cached service data is a third data volume. In response to the MT request message, the access and mobility management network element may determine the reachability status of the terminal, such as determining that the terminal is currently unreachable. The access and mobility management network element may send an MT response message, such as an MT enable UE reachability response message, to the session management network element in response to the MT request message, indicating that the terminal is unreachable. The first information may also be carried in the MT response message.

[0157] It is understood that the aforementioned process of the access and mobility management element triggering the session management element to cache downlink data typically involves, before downlink data arrives and triggers the session management element to query the access and mobility management element for the reachability of the terminal, if the access and mobility management element has already multiplexed the PDU Session Context Update message to send the first information to the session management element. Then, when the terminal's service data initially arrives at the user plane network element, the session management element may choose not to trigger the MT message and wait until a timer expires before reporting the amount of the terminal's service data cached in the network as of the timer expiration to the access and mobility management element. Of course, if the access and mobility management element does not multiplex the PDU Session Context Update message to send the first information to the session management element, then when the session management element initially reports the amount of the terminal's service data via the MT Enable UE Reachability Request message, the access and mobility management element may take this opportunity to send the first information to the session management element, enabling the session management element to subsequently report as needed.

[0158] Optionally, the access and mobility management network element may further determine a duration of the first timer based on a discontinuous reception parameter of the terminal. The duration of the first timer may be a maximum waiting delay, which may indicate how long it takes for the terminal to be reachable, such as how long it takes for the terminal to wake up from eDRX.

[0159] For example, the access and mobility management network element may determine the duration of the first timer based on the timing when the terminal's state indicated by the discontinuous reception parameter changes to a reachable state and the timing when the session management network element starts the first timer, to ensure that the first timer can time out when or before the terminal's state changes to a reachable state, thereby ensuring that the access and mobility management network element can obtain the data volume corresponding to the first QoS flow in a timely manner. Specifically, when the access and mobility management network element determines the timing of sending the first information and the protocol predefines a mechanism for the session management network element to start the first timer, assuming that the mechanism for starting the first timer is that the session management network element receives the first information, the access and mobility management network element may determine the timing when the session management network element starts the first timer accordingly.

[0160] It should be noted that the mechanism of the session management network element starting the first timer can also start the first timer when the first information is received and the preset time has passed to ensure that the first timer times out before the terminal state changes to the reachable state, without restriction.

[0161] For another example, the access and mobility management network element may determine the timing for the access and mobility management network element to send an N2 message to the access network device to trigger paging based on the timing when the terminal state indicated by the discontinuous reception parameter changes to a reachable state. Furthermore, the access and mobility management network element may determine the duration of the first timer based on the timing when the access and mobility management network element sends an N2 message to the access network device to trigger paging and the timing when the session management network element starts the first timer, to ensure that the first timer expires before or at the time when the access and mobility management network element triggers the RAN to perform paging, and to ensure that the access and mobility management network element can obtain the data volume corresponding to the first QoS flow in a timely manner.

[0162] The access and mobility management network element may also send the duration of the first timer to the session management network element. For example, the duration of the first timer may also be carried in the first information, so that it is carried in the same information as the first indication information, thereby reducing the number of communications. However, this is not a limitation, and the two may also be carried in different information to achieve decoupling and more flexible information element transmission. Among them, the access and mobility management network element sending the duration of the first timer to the session management network element is an example. For example, if the session management network element locally pre-configures or pre-defines the duration of the first timer, the access and mobility management network element may not send the duration of the first timer to the session management network element.

[0163] It is understood that the first timer can be configured at the granularity of a QoS flow. For example, if the duration of the first timer corresponds to the identifier of the first QoS flow in the first information, then the first timer is configured for the first QoS flow, such as one or more QoS flows. In this case, when the first timer corresponding to a QoS flow times out, the session management network element reports the data volume corresponding to the QoS flow. Alternatively, the session management network element may configure the first timer at the granularity of a QoS flow by default.

[0164] Mode 3: The first information includes second indication information, and the second indication information is used to instruct the session management network element to report the amount of cached service data of the terminal when the amount of cached service data of the terminal reaches a cached data amount threshold.

[0165] Specifically, the data volume of the cached service data corresponding to one or more QoS flows of the terminal is reported. For example, if the QoS flow corresponding to the cached service data of the terminal, such as the first QoS flow, supports SDT DRB, the cached data volume threshold may be the data volume threshold that the SDT DRB of the access network device can carry, or be determined based on the data volume threshold. In other words, if the data volume of the cached service data of the terminal does not reach the cached data volume threshold, the access network device can perform MT SDT even if the session management network element does not report. However, if the data volume of the cached service data of the terminal reaches the cached data volume threshold, the session management network element should promptly report to the access and mobility management network element, so that the access network device can decide not to perform MT SDT based on the data volume of the cached service data from the access and mobility management network element, so that the access network device can promptly restore the terminal to the connected state for data transmission, thereby reducing transmission delay. The data volume threshold that the SDT DRB can carry may be obtained in advance by the access and mobility management network element from other network elements (such as the access network device), or may be pre-configured by the access and mobility management network element or predetermined by the protocol. For another example, the cache data volume threshold can also be dynamically determined by the access and mobility management network element. For example, if the current load of the network is high, the access and mobility management network element dynamically determines a smaller cache data volume threshold. Conversely, if the current load of the network is low, the access and mobility management network element dynamically determines a larger cache data volume threshold.

[0166] It is understood that, similar to the above-mentioned method 2, the first information can also be carried in a PDU session context update message or an MT response message, that is, reusing existing message implementations to reduce the implementation complexity of the solution. For details, please refer to the relevant introduction of the above-mentioned method 2 and will not be repeated here. Alternatively, the first information can also be carried in a new message to achieve decoupling from the existing message and more flexible information element transmission.

[0167] Optionally, the access and mobility management network element may further send a buffered data volume threshold to the session management network element. For example, the buffered data volume threshold may be carried in the first information and carried in the same information as the second indication information to reduce the number of communications. Of course, the buffered data volume threshold and the second indication information may also be carried in different information to achieve decoupling and more flexible information element delivery. It will be understood that the access and mobility management network element sending the buffered data volume threshold to the session management network element is an example. For example, if the session management network element locally pre-configures or pre-defines a buffered data volume threshold, the access and mobility management network element may not send the buffered data volume threshold to the session management network element.

[0168] It can be understood that for the session management network element, the cached data volume threshold can be configured with QoS flow as the granularity. For example, the cached data volume threshold corresponds to the identifier of the first QoS flow in the first information, so the cached data volume threshold is configured to one or more first QoS flows. In this case, if the data volume corresponding to a QoS flow exceeds the cached data volume threshold corresponding to the QoS flow, the session management network element will report the data volume corresponding to the QoS flow. Alternatively, the session management network element may also default to the cached data volume threshold with QoS flow as the granularity. In addition, the value of the cached data volume threshold corresponding to each QoS flow may be the same or different. For example, in the case where each QoS flow supports SDT DRB, the cached data volume threshold corresponding to each QoS flow is the data volume threshold that the SDT DRB corresponding to each QoS flow can carry. At this time, the data volume thresholds that these SDT DRBs can carry may be different.

[0169] Mode 4: The first information includes third indication information, and the third indication information is used to instruct the session management network element to report the data volume of the terminal's service data each time the network receives service data from the terminal when the terminal is in an inactive and unreachable state.

[0170] In this way, the session management network element can report the amount of service data cached by the network during the entire unreachable state of the terminal, thereby improving the accuracy of the MT SDT decision.

[0171] It is understood that, similar to the above-mentioned method 2, the first information can also be carried in a PDU session context update message or an MT response message, that is, reusing existing message implementations to reduce the implementation complexity of the solution. For details, please refer to the relevant introduction of the above-mentioned method 2 and will not be repeated here. Alternatively, the first information can also be carried in a new message to achieve decoupling from the existing message and more flexible information element transmission.

[0172] It is also understood that the session management network element may also report the amount of data received by the network at each time based on the granularity of the QoS flow based on the third indication information. For example, the third indication information corresponds to the identifier of the first QoS flow in the first information, indicating that each time the network receives data corresponding to a QoS flow in the first QoS flow (e.g., one or more QoS flows), the session management network element reports the amount of data corresponding to that QoS flow. Alternatively, the session management network element may default to reporting the amount of data received by the network at each granularity based on the QoS flow.

[0173] It can also be understood that the unreachable state of the terminal in the inactive state is associated with the terminal being in the inactive state and being configured with discontinuous reception parameters, such as the terminal device in the inactive state being configured with an eDRX parameter with a long eDRX cycle. That is to say, configuring a long eDRX cycle for the inactive terminal means that the terminal is unreachable in the inactive state, or in other words, the terminal entering the inactive state is configured with a long eDRX cycle, which causes the terminal device in the inactive state to be unreachable.

[0174] S302: The session management network element sends a first data volume to the access and mobility management network element according to the first information.

[0175] Accordingly, the access and mobility management network element receives the first data volume from the session management network element.

[0176] The first data volume may be the data volume of cached service data of the terminal, or the data volume of cached service data corresponding to the first QoS flow.

[0177] It should be understood that since the first QoS flow can be one or more QoS flows, the first data volume can also include one or more data volumes. For example, in the case of multiple QoS flows, the first data volume can include the data volumes corresponding to each of the multiple QoS flows. Specifically, the session management network element can send the identifiers of the multiple QoS flows and the data volumes corresponding to the multiple QoS flow identifiers to the access and mobility management network element.

[0178] It should also be understood that, for different implementations of the first information, the session management network element reports the first data volume in different ways, which will be described below in conjunction with the above-mentioned ways 1 to 4.

[0179] With respect to the above-mentioned method 1, the session management network element receives the first information and sends the first data volume to the access and mobility management network element.

[0180] Specifically, when the session management network element caches the service data of the terminal, the session management network element can obtain the first data volume locally after receiving the first information, and report it to the access and mobility management network element; or, when the user plane network element caches the service data of the terminal, the session management network element can find the user plane network element of the terminal based on the received first information, and obtain the first data volume from the user plane network element, and report it to the access and mobility management network element.

[0181] For example, based on the first information, the session management network element may send third information, such as a first N4 session modification message carrying the third information, to the user plane network element of the terminal to trigger the user plane network element to report the data volume of the terminal's service data. The third information may or may not include the identifier of the first QoS flow. The specific principles for this are similar to those for the first information and can be understood with reference thereto, and are not further described here. The third information may be the same as the first information, that is, the session management network element may forward the first information to the user plane network element. Alternatively, the third information may be different from the first information, such as when the session management network element converts the first information into a cell format recognizable by the user plane network element to obtain the third information. Upon receiving the third information, the user plane network element sends the first data volume, such as a second N4 session modification message carrying the first data volume, to the session management network element. Accordingly, the session management network element may receive the first data volume sent by the user plane network element and send a session context response message carrying the first data volume to the access and mobility management network element in response to the aforementioned session context request message. Optionally, as described above, the session context response message may further include an identifier of the first QoS flow, that is, indicating that the first data volume is the data volume corresponding to the first QoS flow.

[0182] It is understood that if the session management network element has previously triggered a paging process via an MT request message, and has previously reported a third data volume, then the first data volume reported by the session management network element at this time may be an increment compared to the third data volume, that is, the increment is obtained by subtracting the third data volume from the volume of service data of the terminal cached by the network as of the time the first message was received. Alternatively, if the session management network element has not previously reported the third data volume, then the first data volume reported by the session management network element at this time may be the total volume, that is, the volume of service data of the terminal cached by the network as of the time the first message was received. Alternatively, regardless of whether the session management network element has previously reported the third data volume, the first data volume reported by the session management network element at this time may be the total volume.

[0183] For the above-mentioned method 2, the session management network element starts the first timer according to the received first indication information (refer to case 11), or triggers the user plane network element to start the second timer (refer to case 12).

[0184] Case 11:

[0185] In one example, upon receiving the duration of the first timer from the access and mobility management network element, the session management network element sets the duration of the first timer according to the received duration, and starts the first timer upon receiving the first indication information.

[0186] In another example, the session management network element is locally preconfigured with the duration of the first timer, and the session management network element may start the first timer upon receiving the first indication information.

[0187] Furthermore, when the first timer expires, the session management network element may send the first data volume to the access and mobility management network element. For example, the session management network element may trigger acquisition of the first data volume based on the expiration of the first timer and send the first data volume to the access and mobility management network element. Optionally, the session management network element may also send an identifier of the first QoS flow, indicating that the first data volume is the data volume corresponding to the first QoS flow.

[0188] Similar to the above-described method 1, if the session management network element caches the terminal's service data, the session management network element can obtain the first data volume locally and report it to the access and mobility management network element. If the user plane network element caches the terminal's service data, the session management network element can obtain the first data volume from the user plane network element. For specific implementation, please refer to the relevant description of the above-described method 1 and will not be repeated here. In this manner, the session management network element can send the first data volume to the access and mobility management network element, such as a Namf_MT service message carrying the first data volume. Optionally, the NamfMT service message may also include an identifier for the first QoS flow, indicating that the first data volume corresponds to the first QoS flow.

[0189] Case 12:

[0190] In the case that the user plane network element caches the service data of the terminal, the session management network element may trigger the user plane network element to start the second timer.

[0191] The session management network element may also send third information to the user plane network element of the terminal based on the first information. The specific implementation is similar to the above-mentioned method 1 and can be understood by reference, but the difference is that the third information may include fourth indication information. The fourth indication information may be used to instruct the user plane network element to report the amount of cached service data of the terminal when the second timer expires. The second timer may be a timer of the user plane network element. The fourth indication information may be the same information as the first indication information, that is, the session management network element may forward the first information (including the first indication information) to the user plane network element. Alternatively, the fourth indication information may be different information from the first indication information, that is, the session management network element may send the fourth indication information to the user plane network element based on the first indication information. For example, the session management network element may convert the first indication information into a cell format that the user plane network element can recognize, obtain the fourth indication information, and then send the third information carrying the fourth indication information to the user plane network element.

[0192] Optionally, the session management network element may also send a second timer duration to the user plane network element. The second timer duration may be the same as or different from the first timer duration. For example, taking into account the processing and communication delays of the session management network element, the session management network element may subtract the processing delay of the session management network element and / or the communication delay between the session management network element and the user plane network element from the first timer duration to obtain the second timer duration. The second timer duration may also be carried in the third information so as to be carried in the same information as the fourth indication information, thereby reducing the number of communications. However, this is not a limitation and the two may also be carried in different information to achieve decoupling and more flexible information element delivery. In addition, the session management network element sending the second timer duration to the user plane network element is an example. For example, if the user plane network element locally preconfigures or predefines the second timer duration, the session management network element may not send the first timer duration to the user plane network element.

[0193] In one example, upon receiving the duration of a second timer from the session management network element, the user plane network element may set the duration of the second timer based on the received duration and start the second timer upon receiving the fourth indication information. In another example, the user plane network element may be locally preconfigured with the duration of the second timer and may start the local second timer upon receiving the fourth indication information. Furthermore, when the second timer expires, the user plane network element may send the first data volume to the session management network element. For example, the user plane network element may trigger acquisition of the first data volume based on the expiration of the second timer and send the first data volume to the session management network element, such as a second N4 session modification message carrying the first data volume. Optionally, the second N4 session modification message may also include an identifier of the first QoS flow, indicating that the first data volume corresponds to the first QoS flow. In this manner, the session management network element may also send the first data volume to the access and mobility management network element, such as a NamfMT service message carrying the first data volume. Optionally, the NamfMT service message may also include an identifier of the first QoS flow, indicating that the first data volume corresponds to the first QoS flow.

[0194] It is understood that the second timer can also be configured at the granularity of a QoS flow. For example, if the duration of the second timer corresponds to the identifier of the first QoS flow in the third information, then the second timer is configured for the first QoS flow, such as one or more QoS flows. In this case, when the first timer corresponding to a QoS flow times out, the user plane network element can report the data volume corresponding to the QoS flow. Alternatively, the user plane network element can also configure the second timer at the granularity of the QoS flow by default.

[0195] It can also be understood that in mode 2, the first data amount reported by the session management network element or the user plane network element can also be an increment or a total amount. The principle is similar to that of the above-mentioned mode 1, which can be understood by reference and will not be repeated here.

[0196] With respect to the above-mentioned method 3, upon receiving the second indication information, the session management network element reports the data volume of the terminal's cached service data or triggers the user plane network element to report the data volume.

[0197] Specifically, the session management network element can determine whether to report the data volume of the service data itself or trigger the user plane network element to report the data volume of the service data based on whether the service data of the terminal is cached locally or in the user plane network element, which are introduced below.

[0198] Case 21: The session management network element caches the service data of the terminal.

[0199] The session management network element may trigger a comparison of the amount of cached service data of the terminal with the cached data amount threshold based on a cached data amount threshold received from the access and mobility management network element. Alternatively, if the session management network element locally pre-configures the cached data amount threshold, the session management network element may trigger a comparison of the amount of cached service data of the terminal with the cached data amount threshold based on the received second indication information. Furthermore, after being triggered, the session management network element may periodically compare the amount of cached service data of the terminal with the cached data amount threshold, or may compare the amount of the latest cached service data of the terminal with the cached data amount threshold when the cached service data of the terminal is updated. If the amount of cached service data of the terminal is less than the cached data amount threshold, the session management network element does not report the amount of cached service data of the terminal. If the amount of cached service data of the terminal is a first amount, i.e., reaches (e.g., is greater than or equal to) the cached data amount threshold, the session management network element may send the first amount of data to the access and mobility management network element, such as a Namf_MT service message carrying the first amount of data. Optionally, the NamfMT service message may also carry the identifier of the first QoS flow, and the first data volume is the data volume corresponding to the first QoS flow.

[0200] It can be understood that since the cache data volume threshold can be configured with QoS flow as the granularity, and the cache data volume threshold corresponding to each QoS flow can also be different, the session management network element can decouple or asynchronously report the data volume corresponding to these QoS flows. For example, if the data volume corresponding to a QoS flow exceeds the cache data volume threshold corresponding to the QoS flow, the session management network element can report the data volume corresponding to the QoS flow, while for the QoS flow that does not exceed the cache data volume threshold, the session management network element will not report the data volume corresponding to the QoS flow.

[0201] Case 22: The user-plane network element caches the terminal's service data.

[0202] The session management network element may also send third information to the user plane network element of the terminal based on the first information. The specific implementation is similar to the above-mentioned method 1 and can be understood by reference, but the difference is that the third information may include fifth indication information. The fifth indication information may be used to instruct the user plane network element to report the data volume of the terminal's cached service data when the data volume of the terminal's cached service data reaches the cached data volume threshold. The fifth indication information and the second indication information may be the same information, that is, the session management network element may forward the first information (including the second indication information) to the user plane network element. Alternatively, the fifth indication information and the second indication information may also be different information, that is, the session management network element may send the fifth indication information to the user plane network element based on the second indication information. For example, the session management network element may convert the second indication information into a cell format that can be recognized by the user plane network element to obtain the fifth indication information, and then send the third information carrying the fifth indication information to the user plane network element.

[0203] Optionally, the session management network element may also send a buffered data volume threshold to the user plane network element. The buffered data volume threshold may also be carried in the third information, so as to be carried in the same information as the fifth indication information, thereby reducing communication overhead. However, this is not a limitation, and the two may also be carried in different information to achieve decoupling and more flexible information element transmission. In addition, the session management network element sending the buffered data volume threshold to the user plane network element is an example. For example, if the user plane network element has a locally pre-configured or pre-defined buffered data volume threshold, the session management network element may not send the buffered data volume threshold to the user plane network element.

[0204] It can be understood that for the user plane network element, the cached data volume threshold can also be configured with QoS flow as the granularity. For example, the cached data volume threshold corresponds to the identifier of the first QoS flow in the third information, then the cached data volume threshold is configured to one or more first QoS flows. In this case, if the data volume corresponding to a QoS flow exceeds the cached data volume threshold corresponding to the QoS flow, the user plane network element will report the data volume corresponding to the QoS flow. Alternatively, the user plane network element can also default to the cached data volume threshold with QoS flow as the granularity. In addition, the value of the user plane threshold corresponding to each QoS flow can be the same, or it can be different.

[0205] The user plane network element may trigger, based on the cached data volume threshold received from the session management network element, to compare the data volume of the terminal's cached service data with the cached data volume threshold. Alternatively, if the user plane network element pre-configures the cached data volume threshold locally, the user plane network element may trigger, based on the received fifth indication information, to compare the data volume of the terminal's cached service data with the cached data volume threshold. Furthermore, after being triggered, the user plane network element may also periodically compare the data volume of the terminal's cached service data with the cached data volume threshold, or may also compare the data volume of the latest terminal's cached service data with the cached data volume threshold when the terminal's cached service data is updated. If the data volume of the terminal's cached service data is less than the cached data volume threshold, the user plane network element does not report the data volume of the terminal's cached service data. If the data volume of the terminal's cached service data is a first data volume, that is, reaches (e.g., is greater than or equal to) the cached data volume threshold, the user plane network element may send the first data volume to the session management network element, such as a second N4 session modification message carrying the first data volume. Optionally, the second N4 session modification message may also include the identifier of the first QoS flow, indicating that the first data volume is the data volume corresponding to the first QoS flow. In this way, the session management network element may also send the first data volume to the access and mobility management network element, such as a Namf service message carrying the first data volume. Optionally, the NamfMT service message may also include the identifier of the first QoS flow, indicating that the first data volume is the data volume corresponding to the first QoS flow.

[0206] It can be understood that since the cache data volume threshold can be configured with QoS flow as the granularity, and the cache data volume threshold corresponding to each QoS flow can also be different, the user-plane network element can decouple or asynchronously report the data volume corresponding to these QoS flows. For example, if the data volume corresponding to a QoS flow exceeds the cache data volume threshold corresponding to the QoS flow, the user-plane network element can report the data volume corresponding to the QoS flow, while for the QoS flow that does not exceed the cache data volume threshold, the user-plane network element will not report the data volume corresponding to the QoS flow.

[0207] With respect to the above-mentioned mode 4, upon receiving the third indication information, the session management network element reports the data volume of the buffered service data of the terminal or triggers the user plane network element to report the data volume.

[0208] Specifically, the session management network element can choose to report the data volume itself or have the user plane network element report the data volume according to whether the terminal service data is cached locally or in the user plane network element, which are introduced below.

[0209] Case 31: The session management network element caches the terminal's service data.

[0210] The session management network element can trigger, based on the third indication information, reporting of the terminal's service data volume each time it receives service data from the terminal. The session management network element can determine whether this reception is complete based on the continuity of received data packets. If so, the volume of service data received from the terminal is the volume of service data received. Otherwise, the session management network element continues to wait until the reception is complete. For example, if the time interval between two adjacent data packets received by the session management network element is less than a time interval threshold, the two adjacent data packets are considered to be received consecutively. Based on this, the session management network element determines that N data packets have been received consecutively, where N is an integer greater than 1. If, after receiving the Nth data packet, the session management network element waits for a period exceeding the time interval threshold without receiving a new data packet, the session management network element determines that this reception is complete. If this reception is complete, the session management network element can send the volume of data received to the access and mobility management network element. Optionally, the first QoS flow identifier is included to indicate that the data volume received is the data volume corresponding to the first QoS flow. Before the terminal's state changes to a reachable state, the session management network element can report the data volume at least once. The first data volume can be the total amount of data reported at least once.

[0211] It can be understood that the session management network element can report at the QoS flow granularity. For example, the session management network element determines which QoS flows in one or more first QoS flows the data corresponding to which are received this time, and then reports the data volume corresponding to these QoS flows. For the QoS flows that do not receive data this time, the session management network element does not report the data volume corresponding to the QoS flow.

[0212] Case 32: The user-plane network element caches the terminal's service data.

[0213] The session management network element may also send third information to the user plane network element corresponding to the terminal based on the first information. The specific implementation is similar to the above-mentioned method 1 and can be understood by reference, but the difference is that the third information may include sixth indication information. The sixth indication information may be used to instruct the user plane network element to report the data volume of the terminal's service data each time it receives service data of the terminal when the terminal is in an inactive and unreachable state. The sixth indication information and the third indication information may be the same information, that is, the session management network element may forward the first information (including the third indication information) to the user plane network element. Alternatively, the sixth indication information and the third indication information may be different information, that is, the session management network element may send the sixth indication information to the user plane network element based on the third indication information. For example, the session management network element may convert the third indication information into a cell format that the user plane network element can recognize, obtain the sixth indication information, and then send the third information carrying the sixth indication information to the user plane network element.

[0214] The user plane network element can trigger reporting of the terminal's service data volume each time it receives buffered service data from the terminal based on sixth indication information received from the session management network element. The user plane network element can also determine whether this reception is complete based on the continuity of received data packets. The specific implementation is similar to that of the aforementioned session management network element and can be understood with reference to this. If this reception is complete, the user plane network element sends the session management network element the data volume of the terminal's service data received this time, such as a data arrival notification message carrying this data volume. Optionally, the data arrival notification message may also include a first QoS flow identifier to indicate that the data volume received this time corresponds to the first QoS flow. Accordingly, the session management network element can continue to report the data volume received by the user plane network element this time to the access and mobility management network element, such as an MT request message carrying this data volume. Optionally, the MT request message may also carry the first QoS flow identifier to indicate that the data volume received this time corresponds to the first QoS flow. Similarly, before the terminal's state transitions to a reachable state, the user plane network element and the session management network element can report the data volume at least once. The first data volume may be the total amount of data reported at least once.

[0215] It can be understood that the user-plane network element can also report at the QoS flow granularity. For example, the user-plane network element determines which QoS flows in one or more first QoS flows the data received this time corresponds to, and then reports the data volume corresponding to these QoS flows. For the QoS flows that did not receive data this time, the user-plane network element does not report the data volume corresponding to the QoS flow.

[0216] It is also understood that the session management network element may report the amount of data received for the first time through an MT process, such as an MT request message. Thereafter, the session management network element may continue to report the amount of data received thereafter through an MT process, such as an MT request message, or other messages, such as a NAMF service message, without specific limitation.

[0217] It is also understandable that the session management network element can obtain whether the service data of the terminal is cached locally or in the user plane network element through pre-configuration or protocol predetermined manner, and the specific implementation method is not limited.

[0218] S303: The access and mobility management network element sends a second data volume to the access network device of the terminal according to the first data volume.

[0219] The second data amount may be the same as or different from the first data amount, which will be introduced below.

[0220] In one possible approach, the second data volume is different from the first data volume. For example, when the first QoS flow includes a QoS flow that supports SDT DRB and a QoS flow that does not support SDT DRB, the first data packet includes the data volume corresponding to the first QoS flow, and the second data volume may be the data volume corresponding to the QoS flow that supports SDT DRB in the first QoS flow. It can be understood that the access and mobility management network element sends the data volume corresponding to the QoS flow that supports SDT DRB to the access network device based on the first data volume to avoid communication redundancy.

[0221] In another possible manner, the second data volume is the same as the first data volume. For example, when the first QoS flow includes a QoS flow that supports SDT DRB and a QoS flow that does not support SDT DRB, the access and mobility management network element can directly send the first data volume to the access network device. Furthermore, when the access network device performs the MT SDT decision, it not only considers the data volume corresponding to the QoS flow that supports SDT DRB, but also considers the data volume corresponding to the QoS flow that does not support SDT DRB. For another example, when the first QoS flow is a QoS flow that supports SDT DRB, the access and mobility management network element can directly send the first data volume to the access network device.

[0222] Optionally, no matter whether the first data volume or the second data volume is reported, the access and mobility management network element may further report identifiers of corresponding QoS flows to indicate that these data volumes are the data volumes corresponding to these QoS flows respectively.

[0223] It is understood that the implementation of S303 is an example and not a limitation. For example, when the second data volume is different from the first data volume, the user plane network element may send the second data volume to the session management network element based on the first data volume, or the session management network element may send the second data volume to the access and mobility management network element based on the first data volume. In this way, the access and mobility management network element may also send the second data volume directly to the access network device.

[0224] In summary, the access and mobility management network element can actively instruct the session management network element to report the data volume of service data, such as the first data volume of service data cached by the network when the terminal is in an inactive state, so that the access and mobility management network element can inform the access network device of the corresponding data volume, such as the second data volume, so that the access network device can make a more accurate MT SDT judgment.

[0225] Optionally, in combination with the above method, before S301, the method may further include:

[0226] S300: An access and mobility management network element receives second information from an access network device.

[0227] The second information may be carried in an N2 message or any other possible message. The second information may include information about the first QoS flow, so that the access and mobility management network element may send the first information to the session management network element based on the information about the first QoS flow. The information about the first QoS flow may include at least one of the following: an identifier of the first QoS flow, a PDU session identifier, SDT indication information, SDT enabling information, or a data volume threshold for an SDT DRB.

[0228] The identifier of the first QoS flow can be used to indicate the first QoS flow. Further, the access and mobility management network element can send first information carrying the identifier of the first QoS flow to the session management network element based on the identifier of the first QoS flow in the information of the first QoS flow.

[0229] It can be understood that when the second information does not include the identifier of the first QoS flow, the access and mobility management network element can obtain and report by default the amount of cached service data corresponding to all QoS flows of the terminal or the amount of cached data corresponding to all QoS flows that have cached downlink data or have downlink data arriving.

[0230] It can be understood that the access and mobility management network element can obtain and report the data volume of cached service data corresponding to which QoS flows of the terminal according to the protocol pre-definition, or it can negotiate in advance with the access and mobility management network element and the access network equipment to report the data volume of cached service data corresponding to which QoS flows of the terminal. Furthermore, after receiving the second information, the access and mobility management network element reports the data volume of cached service data corresponding to these QoS flows by default.

[0231] The PDU session identifier can be used to identify the PDU session corresponding to the first QoS flow, so that the access and mobility management network element can determine the session management network element corresponding to the PDU session, so as to be able to send the first information to the session management network element. It can be understood that the PDU session identifier can also be an optional information element in the first QoS flow information. For example, the access and mobility management network element does not need the indication of the PDU session identifier and sends the first information to the session management network element by default.

[0232] The SDT indication information can be used to indicate which QoS flows in the first QoS flow have corresponding DRBs configured with SDT DRBs, so that the access and mobility management network element decides whether to report only the amount of cached service data corresponding to these QoS flows that support SDT DRBs. For example, the SDT indication information corresponds to the identifiers of the QoS flows that support SDT DRBs in the first QoS flow, and is used to indicate that these corresponding QoS flows support SDT DRBs. It can be understood that the SDT indication information is an optional information element in the first QoS flow information, and the QoS flows that support SDT DRBs can also be implicitly indicated in other ways. For example, the first QoS flow contains 5 QoS flows, and by default, the xth to yth QoS flows in the identifier list composed of the identifiers of these 5 QoS flows support SDT DRBs.

[0233] The SDT enabling information can be used to indicate the amount of cached service data reported by the access and mobility management network element to the terminal. For example, the information element of the SDT enabling information can indicate that the terminal currently in the inactive state is configured with an SDT DRB. This implicitly indicates the amount of cached service data reported by the access and mobility management network element by indicating the configuration of the SDT DRB. Alternatively, the information element of the SDT enabling information can also indicate the amount of cached service data reported by the access and mobility management network element to the terminal.

[0234] In other words, SDT enabling information has a coarser granularity than SDT indication information. If the second message carries SDT enabling information, the access and mobility management network element reports the amount of cached service data of the terminal, regardless of whether the QoS flow supports SDT DRBs. However, if the second message carries SDT indication information, the access and mobility management network element may only report the amount of data corresponding to the QoS flows that support SDT DRBs in the terminal's cached service data.

[0235] The data volume threshold of the SDT DRB can be used to indicate the data volume threshold, or the data volume upper limit, that the SDT DRB of the access network device can carry, so as to enable the access and mobility management network element to decide whether to report the data volume to the access and mobility management network element. For example, when the first QoS flow supports the SDT DRB, the access and mobility management network element obtains the data volume of the network cached data reported by the session management network element through the MT process, such as the third data volume mentioned above. At this time, the access and mobility management network element can determine whether the third data volume is less than the data volume threshold. If the third data volume is less than the data volume threshold, the access and mobility management network element sends the first information to the session management network element. That is, when the data volume of the network cached data is less than the data volume upper limit that the SDT DRB can carry, the access and mobility management network element allows the network to continue caching and reporting the data volume. Otherwise, it triggers the access network device to restore the terminal to the connected state.

[0236] Optionally, the data volume threshold of the SDT DRB may be the same for the QoS flow corresponding to each SDT DRB, or may be different, and there is no limitation on this.

[0237] The above describes the overall process of the communication method provided in the embodiment of the present application in combination with Figure 3. The following describes the specific process of the communication method in each scenario in combination with Figures 4-7.

[0238] Figure 4 is a second flow chart of the communication method provided in an embodiment of the present application. The communication method is applicable to the above-mentioned communication system, and mainly involves the interaction between RAN equipment (such as the above-mentioned access network equipment), AMF network elements (such as the above-mentioned access and mobility management network elements), SMF network elements (such as the above-mentioned session management network elements), and UPF network elements (such as the above-mentioned user plane network elements). In this scenario, the AMF network element can instruct the SMF network element to report the amount of cached service data of the UE when the UE is about to be reachable.

[0239] As shown in Figure 4, the process of the communication method is as follows:

[0240] S401: The RAN device releases the UE to an inactive state and configures eDRX parameters in the inactive state.

[0241] The eDRX parameter may be a long eDRX parameter, i.e., an eDRX cycle greater than 10.24s, which is used to indicate when the UE sleeps and / or when it can be awakened in an inactive state. Optionally, the RAN device may also configure SDT DRBs / SRBs for certain DRBs / SRBs, i.e., the RAN device specifies which DRBs / SRBs' data can be transmitted with SDT enabled. In addition, the embodiment of the present application does not limit which DRBs / SRBs the RAN device specifically selects to configure SDT DRBs / SRBs. For example, the RAN device may make the selection based on its own resource usage.

[0242] S402: The RAN device sends an N2 message to the AMF network element.

[0243] The N2 message may include an eDRX parameter, which is an eDRX parameter used by the UE when it enters the RRC inactive state;

[0244] Optionally, information about the first QoS flow may also be included (refer to the relevant introduction of S300). That is, after the UE is released to the inactive state, the RAN device may send the eDRX parameters in the inactive state and the information about the first QoS flow to the AMF network element, so that the AMF network element can perform reachability detection on the UE and report the data volume corresponding to the first QoS flow cached by the network.

[0245] Optionally, SDT enabling information may also be included to indicate that the terminal device currently in the deactivated state is configured with SDT radio bearer resources, or to instruct the access and mobility management network to provide the amount of service data cached by the terminal device in the deactivated state when the network is in an unreachable state. The provision of cached data volume is provided at the granularity of QoS flows.

[0246] S403, the AMF network element sends a PDU session management service context update (Nsmf_PDUSession_update SMContext) message to the SMF network element.

[0247] S404, the SMF network element modifies the N4 session and caches it.

[0248] S405, the SMF network element sends the N1N2 message transfer service (Namf_Communication_N1N2Message Transfer service) to the AMF network element.

[0249] S406: The UE's service data arrives at the UPF network element.

[0250] The service data of the UE may be data corresponding to the first QoS flow, or data to be carried by the first QoS flow. For an introduction to the first QoS flow, reference may be made to the above description of S301 and will not be repeated here.

[0251] S407, the UPF network element sends a data notification message to the SMF network element.

[0252] The data notification message may carry the data volume of the UE's service data, such as the third data volume mentioned above.

[0253] S408, the SMF network element sends an MT enable UE reachability request message to the AMF network element.

[0254] The MT-enabled UE reachability request message may include the third data volume, the identifier of the first QoS flow, and the identifier of the PDU session where the first QoS flow is located, so as to enable the AMF network element to query the reachability of the UE.

[0255] S409: The AMF network element determines that the UE is in an unreachable state.

[0256] The AMF network element may query the corresponding UE based on the identifier of the first QoS flow and the identifier of the PDU session in which the first QoS flow is located. The AMF network element may query the reachability of the UE based on the eDRX parameters of the UE and determine that the UE is in an unreachable state.

[0257] S410, the AMF network element sends a MT enable UE reachability response (Namf_MT_EnableUERechability response) message to the SMF network element.

[0258] When the UE is in an unreachable state, the MT Enable UE Reachable Response message can be used to instruct the AMF network element to reject the request of the SMF network element.

[0259] For example, the MT Enable UE Reachable Response message may include a rejection indication, indicating that the reason the AMF network element rejected the SMF network element is that the UE is in an unreachable state. The MT Enable UE Reachable Response message may also include a maximum waiting delay, which may be determined by the AMF network element based on the UE's eDRX parameters to indicate the maximum waiting time before the UE is likely to be reachable. The SMF network element may determine whether to cache previously received downlink data based on the maximum waiting delay. For example, the SMF network element may instruct the UPF network element to cache the downlink data, or may instruct the UPF network element to send the downlink data to the SMF network element for caching.

[0260] Optionally, if the first QoS flow supports SDT DRB, the AMF network element may also determine whether the third data volume is less than the data volume threshold of the SDT DRB. The data volume threshold of the SDT DRB may be obtained by the AMF network element from the information of the first QoS flow, or the AMF network element may also obtain it from other network elements, such as the UDM network element, or it may also be configured locally in the AMF network element. If the third data volume is less than the data volume threshold of the SDT DRB, the AMF network element sends an MT-enabled UE reachable response message to the SMF network element; otherwise, the AMF network element may trigger the RAN device to restore the UE to the connected state. For the specific implementation, please refer to the relevant introduction of S300 above and will not be repeated here.

[0261] S411, when the UE status changes to reachable state, the AMF network element triggers a query on the UE's service data cached in the network.

[0262] The UE's state transitioning to a reachable state can be understood as the UE's state about to transition to a reachable state. For example, the AMF network element determines, based on the UE's eDRX parameters, that the UE is about to be reachable. That is, the AMF network element is about to trigger the RAN device to page the UE. The AMF network element then determines to query the network cache for the UE's service data. At this point, the AMF network element can determine, based on the PDU session identifier in the information of the first QoS flow, the SMF network elements corresponding to the PDU session, and determine to query these SMF network elements for the network cache for the UE's service data, thereby executing S412.

[0263] For example, the PDU session identifier includes: PDU session #1, PDU session #2 and PDU session #3, PDU session #1 corresponds to SMF network element #1, PDU session #2 and PDU session #3 correspond to SMF network element #2, and the AMF network element determines to query the network cached UE service data from SMF network element #1 and SMF network element #2 respectively.

[0264] Optionally, if the information of the first QoS flow includes SDT indication information, the AMF network element may further select, based on the SDT indication information, to query the data volume corresponding to the QoS flow supporting SDT DRB in the first QoS flow and execute S412. Alternatively, the AMF network element may not select and still query the data volume corresponding to the first QoS flow.

[0265] For ease of understanding, the following takes the AMF network element querying the data volume corresponding to the first QoS flow as an example to introduce:

[0266] S412, the AMF network element sends a service management context acquisition request (Nsmf_SMContext request) message to the SMF network element.

[0267] The AMF network element may send a service management context acquisition request message to the SMF network element when the UE is about to be reachable, or the AMF network element is about to trigger the RAN device to page the UE. The service management context acquisition request message may include first information for triggering the SMF network element to report the amount of cached service data of the UE, such as the amount of data corresponding to the first QoS flow. For specific implementation, please refer to the relevant introduction of method 1 in the above S301, which will not be repeated here.

[0268] S413, the SMF network element obtains the first data volume of the UE's cached service data from the local.

[0269] If the UE's service data is cached by the SMF network element, the SMF network element executes S413.

[0270] S414, the SMF network element sends the first N4 session modification (N4_Session modification) message to the UPF network element.

[0271] The first N4 session modification message may include third information used to trigger the UPF network element to report the amount of cached service data of the UE.

[0272] S415, the UPF network element sends a second N4 session modification message to the SMF network element.

[0273] The second N4 session modification message may include a first data volume of the UE's buffered service data.

[0274] S416, the SMF network element sends a service management context acquisition response (Nsmf_SMContext response) message to the AMF network element.

[0275] The service management context acquisition response message may include a first amount of data.

[0276] It can be understood that the specific implementation of S413-S416 can also refer to the relevant introduction of method 1 in the above S302, which will not be repeated here.

[0277] S417, the AMF network element sends a downlink data notification (DL data notification) message to the RAN device.

[0278] The downlink data notification message may include a second data amount, and the second data amount may be the same as or different from the first data amount. For specific implementation, reference may be made to the relevant introduction of S303 above, which will not be repeated here.

[0279] Figure 5 is a flow chart of the communication method provided in an embodiment of the present application. The communication method is applicable to the above-mentioned communication system, and mainly involves the interaction between RAN equipment (such as the above-mentioned access network equipment), AMF network element (such as the above-mentioned access and mobility management network element), SMF network element (such as the above-mentioned session management network element), and UPF network element (such as the above-mentioned user plane network element). In this scenario, the AMF network element can trigger the SMF network element / UPF network element to start a timer so that when the timer expires, such as when the UE is about to be reachable, the amount of cached service data of the UE is reported.

[0280] As shown in Figure 5, the process of the communication method is as follows:

[0281] S501: The RAN device releases the UE to an inactive state and configures eDRX parameters in the inactive state.

[0282] S502: The RAN device sends an N2 message to the AMF network element.

[0283] Among them, S501-S502 can refer to the relevant introduction of S401-S402 above, and will not be repeated here.

[0284] S503, the AMF network element sends a PDU session context update message to the SMF network element.

[0285] Optionally, the PDU session context update message may carry first information. The first information may include first indication information for instructing the SMF network element to report the amount of service data of the UE when the first timer expires. Optionally, the first information may also include the duration of the first timer, which may cause the first timer to time out when the UE is about to be reachable. For specific implementation, please refer to the relevant introduction of Method 2 in S301 above and will not be repeated here. Optionally, the duration of the first timer may reuse the maximum waiting delay.

[0286] S504, the SMF network element sends the third information to the UPF network element.

[0287] Optionally, the third information may include fourth indication information, used to instruct the UPF network element to report the amount of service data of the UE when the second timer expires. Optionally, the third information may also include the duration of the second timer, which may cause the second timer to time out when the UE is about to be reachable. The specific implementation may also refer to the relevant introduction of method 2 in the above S302, which will not be repeated here.

[0288] It can be understood that S504 is an optional step. If the UE's service data is cached by the UPF network element, the SMF network element executes S504; otherwise, S504 is not executed.

[0289] S505, the SMF network element modifies the N4 session and caches it.

[0290] S506, the SMF network element sends N1N2 message transmission service to the AMF network element.

[0291] S507, the UE's service data arrives at the UPF network element.

[0292] S508, the UPF network element sends a data notification message to the SMF network element.

[0293] S509, the SMF network element sends an MT enable UE reachability request message to the AMF network element.

[0294] S510: The AMF network element determines that the UE is in an unreachable state.

[0295] Among them, S507-S510 can refer to the relevant introduction of S404-S409 above, and will not be repeated here.

[0296] S511, the AMF network element sends an MT-enabled UE reachable response message to the SMF network element.

[0297] The MT-enabled UE reachability response message may carry the information described in S410 above. If the PDU session context update message in S503 does not carry the first information, the MT-enabled UE reachability response message may also carry the first information. In this case, S504 may be executed after S511. That is, executing S504 after executing S503 and executing S504 after executing S511 may be parallel optional implementations.

[0298] It can also be understood that the specific implementation of S511 can also refer to the relevant introduction of method 2 in the above S302, which will not be repeated here.

[0299] S512, the SMF network element obtains the first data volume of the UE's cached service data according to the expiration of the first timer.

[0300] The SMF network element can obtain the first data volume of the UE's cached service data locally, or it can obtain the first data volume of the UE's cached service data from the UPF network element.

[0301] S513: The UPF network element obtains the first data volume of the UE's cached service data from the local device according to the expiration of the second timer.

[0302] S514, the UPF network element sends the first amount of data to the SMF network element.

[0303] S515, the SMF network element sends the first amount of data to the AMF network element.

[0304] It can be understood that S512 and S515 are in an "or" execution relationship with S513-S515. The specific implementation of S512-S515 can also refer to the relevant introduction of the method 2 in S302 above, which will not be repeated here.

[0305] S516, the AMF network element sends a downlink data notification message to the RAN device.

[0306] The downlink data notification message may include the second data volume. For specific implementation, reference may be made to the relevant introduction of S303 above, which will not be repeated here.

[0307] Figure 6 is a fourth flow chart of the communication method provided in an embodiment of the present application. The communication method is applicable to the above-mentioned communication system, and mainly involves the interaction between RAN equipment (such as the above-mentioned access network equipment), AMF network element (such as the above-mentioned access and mobility management network element), SMF network element (such as the above-mentioned session management network element), and UPF network element (such as the above-mentioned user plane network element). In this scenario, the AMF network element sends the cached data volume threshold to the SMF network element / UPF network element, so that when the amount of cached service data of the SMF network element / UPF network element UE reaches the cached data volume threshold, the data volume is reported.

[0308] As shown in Figure 6, the process of the communication method is as follows:

[0309] S601: The RAN device releases the UE to an inactive state and configures eDRX parameters in the inactive state.

[0310] S602: The RAN device sends an N2 message to the AMF network element.

[0311] Among them, S601-S602 can refer to the relevant introduction of S401-S402 above, and will not be repeated here.

[0312] S603, the AMF network element sends a PDU session context update message to the SMF network element.

[0313] The PDU session context update message may carry the first information. The first information may include second indication information for instructing the SMF network element to report the data volume of the UE's cached service data when the data volume of the UE's cached service data reaches the cached data volume threshold. Optionally, the cached data volume threshold may also be included. For specific implementation, reference may be made to the relevant introduction to Mode 3 in S301 above, which will not be repeated here.

[0314] S604, the SMF network element sends the third information to the UPF network element.

[0315] The third information may include fifth indication information, which is used to instruct the UPF network element to report the data volume of the UE's cached service data when the data volume of the UE's cached service data reaches the cached data volume threshold. Optionally, the third information may also include the cached data volume threshold. The specific implementation may also refer to the relevant introduction of method 3 in the above S302, which will not be repeated here.

[0316] It can be understood that S604 is an optional step. If the UE's service data is cached by the UPF network element, the SMF network element executes S604; otherwise, S604 is not executed.

[0317] S605, the SMF network element modifies the N4 session and caches it.

[0318] S606, the SMF network element sends N1N2 message transmission service to the AMF network element.

[0319] S607, the UE's service data arrives at the UPF network element.

[0320] S608, the UPF network element sends a data notification message to the SMF network element.

[0321] S609, the SMF network element sends an MT enable UE reachability request message to the AMF network element.

[0322] S610: The AMF network element determines that the UE is in an unreachable state.

[0323] Among them, S607-S610 can refer to the relevant introduction of S404-S409 above, which will not be repeated here.

[0324] S611, the AMF network element sends an MT-enabled UE reachable response message to the SMF network element.

[0325] The MT-enabled UE reachability response message may carry the information described in S410 above. If the PDU session context update message in S603 does not carry the first information, the MT-enabled UE reachability response message may also carry the first information. In this case, S604 may be performed after S611. That is, performing S604 after S603 and performing S604 after S611 may be parallel optional implementations.

[0326] It can be understood that the specific implementation of S611 can also refer to the relevant introduction of method 3 in the above S302, which will not be repeated here.

[0327] S612, the SMF network element obtains the first data volume of the UE's cached service data from the local according to the data volume of the UE's cached service data reaching the cached data volume threshold.

[0328] S613, the UPF network element obtains the first data volume of the UE's cached service data from the local according to the data volume of the UE's cached service data reaching the cached data volume threshold.

[0329] S614, the UPF network element sends the first amount of data to the SMF network element.

[0330] S615, the SMF network element sends the first amount of data to the AMF network element.

[0331] It can be understood that S612 and S615 are in an "or" execution relationship with S613-S615. The specific implementation of S612-S615 can also refer to the relevant introduction of the method 3 in S302 above, which will not be repeated here.

[0332] S616, the AMF network element sends a downlink data notification message to the RAN device.

[0333] The downlink data notification message may include the second data volume. For specific implementation, reference may be made to the relevant introduction of S303 above, which will not be repeated here.

[0334] Figure 7 is a flowchart of the communication method provided in an embodiment of the present application. The communication method is applicable to the above-mentioned communication system, and mainly involves the interaction between RAN equipment (such as the above-mentioned access network equipment), AMF network element (such as the above-mentioned access and mobility management network element), SMF network element (such as the above-mentioned session management network element), and UPF network element (such as the above-mentioned user plane network element). In this scenario, the AMF network element can instruct the SMF network element / UPF network element to report the corresponding data volume each time it receives and caches UE service data.

[0335] As shown in Figure 7, the process of the communication method is as follows:

[0336] S701: The RAN device releases the UE to an inactive state and configures eDRX parameters in the inactive state.

[0337] S702: The RAN device sends an N2 message to the AMF network element.

[0338] Among them, S701-S702 can refer to the relevant introduction of S401-S402 above, and will not be repeated here.

[0339] S703, the AMF network element sends a PDU session context update message to the SMF network element.

[0340] The PDU session context update message may carry the first information. The first information may include third indication information for instructing the SMF network element to report the data volume of the UE's service data each time the network receives service data from the UE when the terminal is in an inactive and unreachable state. For specific implementation, reference may also be made to the relevant introduction to Mode 4 in S301 above, which will not be repeated here.

[0341] S704, the SMF network element sends the third information to the UPF network element.

[0342] The third information may include sixth indication information, which is used to instruct the UPF network element to report the amount of UE's business data each time the network receives UE's business data when the terminal is in an inactive and unreachable state. The specific implementation can also refer to the relevant introduction of method 4 in the above S302, which will not be repeated here.

[0343] It can be understood that S704 is an optional step. If the UE's service data is cached by the UPF network element, the SMF network element executes S704; otherwise, S704 is not executed.

[0344] S705, the SMF network element modifies the N4 session and caches it.

[0345] S706, the SMF network element sends N1N2 message transmission service to the AMF network element.

[0346] S707, the UE's service data arrives at the UPF network element.

[0347] S708, the UPF network element sends a data notification message to the SMF network element.

[0348] S709, the SMF network element sends an MT enable UE reachability request message to the AMF network element.

[0349] S710: The AMF network element determines that the UE is in an unreachable state.

[0350] Among them, S707-S710 can refer to the relevant introduction of S404-S409 above, which will not be repeated here.

[0351] S711, the AMF network element sends an MT-enabled UE reachable response message to the SMF network element.

[0352] The MT-enabled UE reachability response message may carry the information described in S410 above. If the PDU session context update message in S603 does not carry the first information, the MT-enabled UE reachability response message may also carry the first information. In this case, S604 may be executed after S611. That is, executing S704 after executing S703 and executing S704 after executing S711 may be parallel optional implementations.

[0353] It can be understood that the specific implementation of S611 can also refer to the relevant introduction of method 4 in the above S302, which will not be repeated here.

[0354] S712, the SMF network element obtains the amount of UE service data received by the network this time.

[0355] S713, the UPF network element obtains the amount of UE service data received by the network this time.

[0356] S714, the UPF network element sends the amount of UE service data received by the network this time to the SMF network element.

[0357] S715, the SMF network element sends the amount of UE service data received by the network this time to the AMF network element.

[0358] It can be understood that S712 and S715 are in an "or" execution relationship with S713-S715. The specific implementation of S712-S715 can also refer to the relevant introduction of the method 4 in S302 above, which will not be repeated here.

[0359] It can also be understood that S707-S715 can be repeated multiple times to realize the data volume of the UE's service data received by the network each time. Alternatively, only S707 and S712-S715 can be repeatedly executed. If the AMF network element sends the first information to the SMF network element through S703, the subsequent execution of S707-S715 can be considered as the first time that the UPF network element / SMF network element reports the data volume. If the AMF network element sends the first information to the SMF network element through S711, the subsequent repetition of S707-S715 or S707, S712-S715 can be considered as the first time that the UPF network element / SMF network element reports the data volume.

[0360] S716, the AMF network element sends a downlink data notification message to the RAN device.

[0361] The downlink data notification message may include the second data volume. For specific implementation, reference may be made to the relevant introduction of S303 above, which will not be repeated here.

[0362] Figure 8 is a flow chart 5 of the communication method provided in an embodiment of the present application. This communication method is applicable to the above communication system, and mainly involves the interaction between the access and mobility management network element and the terminal.

[0363] As shown in Figure 8, the process of the communication method is as follows:

[0364] S801: An access and mobility management network element receives signaling to be sent to a terminal in an unreachable state.

[0365] Among them, the signaling can be other network elements in the network, such as data management network elements (UDM / UDR network elements), session management network elements (SMF network elements), etc., which are sent to the terminal through the access and mobility management network element. The specific signaling type is not limited in the embodiment of this application. At this time, when the access and mobility management network element receives the signaling, the terminal is in an unreachable state in an inactive state. How the access and mobility management network element determines that the terminal is in an unreachable state in an inactive state can be referred to the relevant introduction of the above embodiment, and will not be repeated here.

[0366] S802: The access and mobility management network element sends signaling related information to the access network device of the terminal.

[0367] The signaling-related information can be used by the access network device to determine whether the small data transmission (SDT) is used to transmit signaling. For example, the signaling-related information includes the signaling data volume. When the terminal's state changes to a reachable state, for example, the access and mobility management network element can determine, based on the terminal's eDRX parameters, that the terminal's state has changed to a reachable state, and thus send the signaling-related information to the access network device. In other words, the access and mobility management network element can send the access network device the entire signaling data volume to be sent to the terminal during the entire unreachable state of the terminal, thereby improving the accuracy of the MT SDT decision.

[0368] In summary, when the access and mobility management network element receives signaling to be sent to a terminal in an unreachable state, it can inform the access network device of relevant information (such as data volume) of the signaling so that the access network device can make a more accurate MT SDT decision.

[0369] The communication method provided in the embodiment of the present application is described in detail above in conjunction with Figures 3 to 8. The communication device for executing the communication method provided in the embodiment of the present application is described in detail below in conjunction with Figures 9 and 10.

[0370] Figure 9 is a structural diagram of a communication device according to an embodiment of the present application. As shown in Figure 9 , the communication device 900 includes a transceiver module 901 and a processing module 902. For ease of illustration, Figure 9 only shows the main components of the communication device.

[0371] In some embodiments, the communication device 900 may be an access and mobility management network element in the method shown in FIG. 3 or FIG. 8 , or an AMF network element in the method shown in FIG. 5 to FIG. 7 .

[0372] Among them, the transceiver module 901 is used to implement the transceiver function of the access and mobility management network element or AMF network element in the above method, such as executing S302, and the processing module 902 is used to implement other functions of the access and mobility management network element or AMF network element in the above method except the transceiver function, such as executing S301.

[0373] Optionally, the transceiver module 901 may include a sending module (not shown in FIG9 ) and a receiving module (not shown in FIG9 ). The sending module is used to implement the sending function of the communication device 900 , and the receiving module is used to implement the receiving function of the communication device 900 .

[0374] Optionally, the communication device 900 may further include a storage module (not shown in FIG. 9 ), which stores a program or instruction. When the processing module 902 executes the program or instruction, the communication device 900 may perform the functions of the network device (such as the access and mobility management network element or AMF network element) in the method shown in FIG. 3 to FIG. 8 in the above method.

[0375] It can be understood that the communication device 900 can be a network device, such as an access and mobility management network element or an AMF network element, or a chip (system) or other parts or components that can be set in the network device, or a device that includes a network device. This application does not limit this.

[0376] In addition, the technical effects of the communication device 900 can refer to the technical effects of the communication method shown in Figures 3 to 8, and will not be repeated here.

[0377] In other embodiments, the communication device 900 may be a session management network element in the method shown in FIG. 3 , or an SMF network element in the methods shown in FIG. 5 to FIG. 7 .

[0378] Among them, the transceiver module 901 is used to implement the transceiver function of the session management network element or SMF network element in the above method, such as executing S301, and the processing module 902 is used to implement other functions of the session management network element or SMF network element in the above method except the transceiver function, such as executing S302.

[0379] Optionally, the transceiver module 901 may include a sending module (not shown in FIG9 ) and a receiving module (not shown in FIG9 ). The sending module is used to implement the sending function of the communication device 900 , and the receiving module is used to implement the receiving function of the communication device 900 .

[0380] Optionally, the communication device 900 may further include a storage module (not shown in FIG. 9 ) storing a program or instruction. When the processing module 902 executes the program or instruction, the communication device 900 may perform the functions of a network device (such as a session management network element or an SMF network element) in the method shown in FIG. 3 to FIG. 8 in the above method.

[0381] It can be understood that the communication device 900 can be a network device, such as a session management network element or an SMF network element, or a chip (system) or other parts or components that can be set in the network device, or a device that includes a network device. This application does not limit this.

[0382] In addition, the technical effects of the communication device 900 can refer to the technical effects of the communication method shown in Figures 3 to 8, and will not be repeated here.

[0383] Figure 10 is a second structural diagram of a communication device provided in an embodiment of the present application. Exemplarily, the communication device may be a network device, such as an access and mobility management network element or a session management network element, such as an AMF network element or an SMF network element, or a chip (system) or other component or assembly that can be set in a network device. As shown in Figure 10, the communication device 1000 may include a processor 1001. Optionally, the communication device 1000 may further include a memory 1002 and / or a transceiver 1003. The processor 1001 is coupled to the memory 1002 and the transceiver 1003, such as by being connected via a communication bus.

[0384] The following is a detailed introduction to the various components of the communication device 1000 in conjunction with FIG10 :

[0385] The processor 1001 is the control center of the communication device 1000 and can be a single processor or a collective term for multiple processing elements. For example, the processor 1001 can be one or more central processing units (CPUs), an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present application, such as one or more digital signal processors (DSPs) or one or more field programmable gate arrays (FPGAs).

[0386] Optionally, the processor 1001 can execute various functions of the communication device 1000 by running or executing software programs stored in the memory 1002 and calling data stored in the memory 1002, such as executing the communication method shown in Figures 3 to 8 above.

[0387] In a specific implementation, as an embodiment, the processor 1001 may include one or more CPUs, such as CPU0 and CPU1 shown in FIG10 .

[0388] In a specific implementation, as an embodiment, the communication device 1000 may also include multiple processors, such as the processor 1001 and the processor 1004 shown in FIG10 . Each of these processors may be a single-core processor (single-CPU) or a multi-core processor (multi-CPU). The processor herein may refer to one or more devices, circuits, and / or processing cores for processing data (e.g., computer program instructions).

[0389] The memory 1002 is used to store the software program for executing the solution of the present application, and the execution is controlled by the processor 1001. The specific implementation method can refer to the above method embodiment and will not be repeated here.

[0390] Alternatively, the memory 1002 may be a read-only memory (ROM) or other type of static storage device that can store static information and instructions, a random access memory (RAM) or other type of dynamic storage device that can store information and instructions, or an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, an optical disc storage (including a compact disc, laser disc, optical disc, digital versatile disc, Blu-ray disc, etc.), a magnetic disk storage medium or other magnetic storage device, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and can be accessed by a computer, but is not limited thereto. The memory 1002 may be integrated with the processor 1001 or exist independently and be coupled to the processor 1001 via an interface circuit (not shown in FIG. 10 ) of the communication device 1000. This embodiment of the present application does not specifically limit this.

[0391] Transceiver 1003 is used for communication with other communication devices. For example, if communication device 1000 is a terminal, transceiver 1003 can be used to communicate with a network device or another terminal device. For another example, if communication device 1000 is a network device, transceiver 1003 can be used to communicate with a terminal or another network device.

[0392] Optionally, the transceiver 1003 may include a receiver and a transmitter (not shown separately in FIG10 ), wherein the receiver is used to implement a receiving function, and the transmitter is used to implement a sending function.

[0393] Optionally, the transceiver 1003 may be integrated with the processor 1001 or exist independently and be coupled to the processor 1001 through an interface circuit (not shown in FIG. 10 ) of the communication device 1000 . This embodiment of the present application does not specifically limit this.

[0394] It is understandable that the structure of the communication device 1000 shown in FIG10 does not constitute a limitation on the communication device, and an actual communication device may include more or fewer components than shown in the figure, or combine certain components, or arrange the components differently.

[0395] In addition, the technical effects of the communication device 1000 can refer to the technical effects of the methods described in the above method embodiments, and will not be repeated here.

[0396] An embodiment of the present application provides a communication system, which includes: an access and mobility management network element and a session management network element for executing the method shown in Figure 3, or an AMF network element and an SMF network element for executing the method shown in Figures 4-7, or an access and mobility management network element and an access network device for executing the method shown in Figure 8.

[0397] An embodiment of the present application provides a computer-readable storage medium, including: a computer program or instructions; when the computer program or instructions are executed on a computer, the computer is caused to execute the method corresponding to any of the above-mentioned Figures 3 to 8.

[0398] An embodiment of the present application provides a computer program product, including a computer program or instructions. When the computer program or instructions are executed on a computer, the computer executes the method corresponding to any of the above-mentioned Figures 3 to 8.

[0399] It should be understood that the processor in the embodiments of the present application may be a central processing unit (CPU), and the processor may also be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor, etc.

[0400] It should also be understood that the memory in the embodiments of the present application may be a volatile memory or a non-volatile memory, or may include both volatile and non-volatile memories. Among them, the non-volatile memory may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory may be a random access memory (RAM), which is used as an external cache. By way of example and not limitation, many forms of random access memory (RAM) are available, such as static RAM (SRAM), dynamic random access memory (DRAM), synchronous DRAM (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous link DRAM (SLDRAM), and direct rambus RAM (DR RAM).

[0401] The above embodiments can be implemented in whole or in part by software, hardware (such as circuits), firmware or any other combination. When implemented using software, the above embodiments 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 or computer programs. When the computer instructions or computer program are loaded or 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 a wired (such as infrared, wireless, microwave, etc.) method. The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server or data center that contains one or more available media sets. The available medium can be a magnetic medium (for example, a floppy disk, a hard disk, a tape), an optical medium (for example, a DVD), or a semiconductor medium. The semiconductor medium can be a solid-state drive.

[0402] It should be understood that the term "and / or" as used herein simply describes a relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A alone, A and B together, or B alone. A and B can be singular or plural. Furthermore, the character " / " as used herein generally indicates an "or" relationship between the associated objects, but it may also indicate an "and / or" relationship. For specific understanding, please refer to the context.

[0403] In this application, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can mean: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or plural.

[0404] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0405] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0406] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0407] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of the units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0408] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0409] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0410] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0411] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A communication method, characterized in that: The method comprises: The access and mobility management network element sends first information to the session management network element, wherein the first information is used to trigger the session management network element to report the amount of cached service data of the terminal, where the cached service data of the terminal is service data cached by the network when the terminal is in an inactive state; The access and mobility management network element receives a first data volume from the session management network element, where the first data volume is a data volume of cached service data of the terminal; The access and mobility management network element sends a second amount of data to an access network device of the terminal according to the first amount of data.

2. The method according to claim 1, characterized in that The access and mobility management network element sends first information to the session management network element, including: When the state of the terminal changes to a reachable state, the access and mobility management network element sends the first information to the session management network element.

3. The method according to claim 2, characterized in that The method further comprises: The access and mobility management network element determines that the state of the terminal changes to a reachable state.

4. The method according to claim 2 or 3, characterized in that: The first information is carried in a session context request message, and the first data volume is carried in a session context response message.

5. The method according to claim 1, characterized in that The first information includes first indication information, where the first indication information is used to instruct the session management network element to report the amount of cached service data of the terminal when a first timer times out.

6. The method according to claim 5, characterized in that The method further comprises: The access and mobility management network element determines, according to the discontinuous reception parameter of the terminal, a duration of the first timer; The access and mobility management network element sends the duration of the first timer to the session management network element.

7. The method according to claim 5 or 6, characterized in that: The first information also includes the duration of the first timer.

8. The method according to claim 1, characterized in that The first information includes second indication information, and the second indication information is used to instruct the session management network element to report the data volume of the cached service data of the terminal when the data volume of the cached service data of the terminal reaches a cached data volume threshold.

9. The method according to claim 8, characterized in that The first information also includes the cache data amount threshold.

10. The method according to claim 8 or 9, characterized in that: The first information is carried in a protocol data unit PDU session context update message, or the first information is carried in a mobile terminal termination MT response message.

11. The method according to claim 1, characterized in that: The first information includes third indication information, and the third indication information is used to instruct the session management network element to report the data volume of the service data of the terminal each time the network receives the service data of the terminal when the terminal is in an inactive and unreachable state.

12. The method according to claim 11, characterized in that The first information is carried in an MT response message, and the first data volume is carried in an MT request message.

13. The method according to any one of claims 1 to 12, characterized in that The first information also includes an identifier of a first quality of service QoS flow of the terminal, where the identifier of the first QoS flow is used to indicate that the cached service data of the terminal is data corresponding to the first QoS flow.

14. The method according to claim 13, characterized in that The first QoS flow supports SDT DRB small data transmission data bearer.

15. The method according to claim 14, characterized in that The method further comprises: The access and mobility management network element receives second information from an access network device of the terminal, wherein the second information includes information of the first QoS flow; The access and mobility management network element sends the first information to the session management network element, including: The access and mobility management network element sends the first information to the session management network element according to the information of the first QoS flow.

16. The method according to claim 15, characterized in that The second information further includes a data volume threshold of the SDT DRB, and the access and mobility management network element sends the first information to the session management network element, including: When the amount of data cached by the network is less than the data amount threshold of the SDT DRB, the access and mobility management network element sends the first information to the session management network element, wherein the data cached by the network is data corresponding to the first QoS flow.

17. The method according to any one of claims 1 to 16, characterized in that: The first data volume includes the data volume corresponding to at least one QoS flow of the terminal, and the second data volume is the data volume corresponding to the QoS flow supporting SDT DRB in the at least one QoS flow; or, The first data amount is the same as the second data amount.

18. The method according to any one of claims 1 to 17, characterized in that Before the access and mobility management network element sends the first information to the session management network element, the method further includes: The access and mobility management network element receives the session management network element mobile terminal termination MT request message, wherein the MT request message includes a third data amount, and the third data amount is the data amount of the cached service data of the terminal; When the terminal is in an inactive and unreachable state, the access and mobility management network element sends an MT response message to the session management network element according to the MT request message, wherein the MT response message is used to indicate that the terminal is unreachable.

19. A communication method, characterized in that: The method comprises: The session management network element receives first information from the access and mobility management network element, wherein the first information is used to trigger the session management network element to report the amount of cached service data of the terminal, where the cached service data of the terminal is service data cached by the network when the terminal is in an inactive state; The session management network element sends a first data volume to the access and mobility management network element according to the first information, where the first data volume is a data volume of cached service data of the terminal.

20. The method according to claim 19, characterized in that The first information is carried in a session context request message, and the first data volume is carried in a session context response message.

21. The method according to claim 19, characterized in that The first information includes first indication information, where the first indication information is used to instruct the session management network element to report the amount of service data of the terminal when the first timer times out; The session management network element sending a first amount of data to the access and mobility management network element according to the first information includes: When the first timer times out, the session management network element sends the first data volume to the access and mobility management network element.

22. The method according to claim 21, characterized in that The method further comprises: The session management network element starts the first timer when receiving the duration of the first timer from the access and mobility management network element.

23. The method according to claim 21 or 22, characterized in that: The first information also includes the duration of the first timer.

24. The method according to claim 19, characterized in that The first information includes second indication information, where the second indication information is used to instruct the session management network element to report the amount of cached service data of the terminal when the amount of cached service data of the terminal reaches a cached data amount threshold; The session management network element sending a first amount of data to the access and mobility management network element according to the first information includes: When the first data amount reaches the buffer data amount threshold, the session management network element sends the first data amount to the access and mobility management network element.

25. The method according to claim 24, characterized in that: The first information carries the cache data amount threshold.

26. The method according to claim 24 or 25, characterized in that The first information is carried in a protocol data unit PDU session context update message, or the first information is carried in a mobile terminal termination MT response message.

27. The method according to claim 19, characterized in that The first information includes third indication information, and the third indication information is used to instruct the session management network element to report the data volume of the service data of the terminal each time the network receives service data of the terminal when the terminal is in an inactive and unreachable state; The session management network element sending a first amount of data to the access and mobility management network element according to the first information includes: When the network receives the cached service data of the terminal, the session management network element sends to the access and mobility management network element that the cached service data received from the terminal this time is the first data volume.

28. The method according to claim 27, characterized in that The first information is carried in an MT response message, and the first data volume is carried in an MT request message.

29. The method according to any one of claims 19 to 28, characterized in that The first information also includes an identifier of a first quality of service QoS flow of the terminal, where the identifier of the first QoS flow is used to indicate that the cached service data of the terminal is data corresponding to the first QoS flow.

30. The method according to claim 29, characterized in that The first QoS flow supports SDT DRB small data transmission data bearer.

31. The method according to any one of claims 19 to 30, characterized in that The method further comprises: The session management network element obtains the first data volume locally from the session management network element according to the first information.

32. The method according to any one of claims 19 to 30, characterized in that The network element in the network includes a user plane network element, and the method further includes: The session management network element obtains the first data volume from the user plane network element according to the first information.

33. A communication device, characterized in that: The apparatus comprises: a module for executing the method as claimed in any one of claims 1-32.

34. A communication device, characterized in that: The communication device comprises: a processor and a memory; the memory is used to store computer instructions, and when the processor executes the instructions, the communication device executes the method according to any one of claims 1-32.

35. A communication system, characterized in that: The communication system comprises: an access and mobility management network element in the method according to any one of claims 1 to 18, and a session management network element in the method according to any one of claims 19 to 32.

36. A computer-readable storage medium, characterized in that: The computer-readable storage medium comprises a computer program or instructions, and when the computer program or instructions are executed on a computer, the computer is caused to perform the method according to any one of claims 1 to 32.

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