Communication method, communication device, and communication system

Abstract

The present application provides a communication method, a communication device, and a communication system. The method includes the steps of: determining sleep time information of a terminal device based on satellite coverage information of the terminal device, the satellite coverage information indicating a time period in which the terminal device is covered by a satellite network and / or a time period in which the terminal device is not covered by a satellite network, and the sleep time period corresponding to the sleep time information includes a time period in which the terminal device is not covered by a satellite network; and transmitting the sleep time information to the terminal device. According to the solution, the sleep time information is determined based on the satellite coverage information of the terminal device, and the sleep time period corresponding to the sleep time information includes a time period in which the terminal device is not covered by a satellite network, so as to ensure that the terminal device sleeps as much as possible during the time period in which the terminal device is not covered by the satellite network, and can avoid unnecessary network connection operations such as cell selection, thereby reducing the power consumption of the terminal device.

Description

Technical Field

[0001] This application relates to the field of communication technologies, and in particular, to communication methods, communication devices, and communication systems.

Background Art

[0003] Currently, in some communication scenarios, for example, in order to ensure the network coverage effect of terminal devices in a massive machine type communications (mMTC) application scenario, satellite communication has been introduced. Satellite communication can improve network coverage to a certain extent.

[0004] However, because the satellite is in a moving state, it may be impossible for the terminal device to be covered by the satellite network during a time period.

Summary of the Invention

[0005] Embodiments of this application provide a communication method, a communication device, and a communication system to reduce the power consumption of a terminal device or a core network device (for example, a mobility management network element) in a satellite-based communication scenario.

[0006] According to a first aspect, an embodiment of the present application provides a communication method. The method can be implemented by a mobility management network element or by a module (e.g., a chip) used by the mobility management network element. The method includes determining sleep time information for a terminal device based on satellite coverage information of the terminal device, where the satellite coverage information indicates a time period during which the terminal device is covered by a satellite network and / or a time period during which the terminal device is not covered by the satellite network, and the sleep time period corresponding to the sleep time information includes a time period during which the terminal device is not covered by the satellite network, and transmitting the sleep time information to the terminal device.

[0007] According to the above solution, the mobility management network element determines sleep time information based on the satellite coverage information of the terminal device, and the sleep time period corresponding to the sleep time information includes a time period during which the terminal device is not covered by the satellite network, so that the terminal device can sleep as much as possible during the time period when it is not covered by the satellite network, avoid unnecessary network connection operations such as cell selection, and ensure that the power consumption of the terminal device can be reduced.

[0008] In a possible implementation manner, one or more of the eDRX cycle, the periodic TAU cycle, or the periodic registration cycle of the terminal device are determined based on the satellite coverage information, the sleep time information includes a sleep start time, and the sleep start time is within the eDRX cycle or the periodic TAU cycle.

[0009] In a possible implementation manner, the sleep time information includes a sleep start time and a sleep end time, or the sleep time information includes a sleep start time and a sleep period.

[0010] According to the foregoing solution, during the sleep time period corresponding to the sleep time information, the terminal device does not execute services, including skipping periodic TAU, periodic registration, and uplink data transmission, so that the power consumption of the terminal device can be reduced.

[0011] In a possible implementation method, satellite coverage information is received, or ephemeris information of the satellite cell where the terminal device is located is received, and the satellite coverage information is determined based on the ephemeris information.

[0012] In a possible implementation method, it is determined that the position of the terminal device is fixed, or the movement trajectory of the terminal device is fixed.

[0013] In a possible implementation method, when the deregistration timer corresponding to the terminal device expires, it is determined based on the satellite coverage information that the terminal device is not covered by the satellite network, and it is also determined to skip performing deregistration on the terminal device.

[0014] According to this solution, when the terminal device is not covered by the satellite network, the mobility management network element does not deregister the terminal device, so that the switching of the status of the terminal device going back and forth between registration and deregistration is reduced, thereby reducing the power consumption of the terminal device and reducing the frequent signaling interaction with the network.

[0015] According to a second aspect, embodiments of the present application provide a communication method. The method can be implemented by a mobility management network element or by a module (e.g., a chip) used by the mobility management network element. The method includes determining, based on satellite coverage information of a terminal device, that the terminal device is not covered by a satellite network when a deregistration timer corresponding to the terminal device expires, where the satellite coverage information indicates a time period during which the terminal device is covered by the satellite network and / or a time period during which the terminal device is not covered by the satellite network, and determining to skip performing deregistration for the terminal device in response to the terminal device not being covered by the satellite network.

[0016] According to this solution, when the terminal device is not covered by the satellite network, the mobility management network element does not deregister the terminal device, thereby reducing the switching of the status of the terminal device that travels back and forth between registration and deregistration, and thus reducing the power consumption of the terminal device. In a possible implementation, first information is sent to the terminal device, and the first information indicates that the terminal device performs uplink transmission based on the satellite network coverage status when the terminal device has uplink transmission requirements.

[0017] In a possible implementation, the first information is satellite coverage information, and the first information clearly indicates that the terminal device starts uplink transmission based on the satellite coverage information when the terminal device has uplink transmission requirements.

[0018] In a possible implementation, the satellite coverage information is sent to the terminal device, and the first information clearly indicates that the terminal device starts uplink transmission based on the satellite coverage information when the terminal device has uplink transmission requirements.

[0019] In a possible implementation method, the uplink transmission requirements include one or more of periodic TAU, periodic registration, or uplink data transmission.

[0020] In a possible implementation method, satellite coverage information is received, or ephemeris information of the satellite cell where the terminal device is located is received, and the satellite coverage information is determined based on the ephemeris information.

[0021] In a possible implementation method, it is determined that the position of the terminal device is fixed, or the movement trajectory of the terminal device is fixed.

[0022] According to a third aspect, an embodiment of the present application provides a communication method. The method can be implemented by a mobility management network element or a module (such as a chip) used by the mobility management network element. The method includes a step of determining satellite coverage information of a terminal device, where the satellite coverage information indicates a time period during which the terminal device is covered by a satellite network and / or a time period during which the terminal device is not covered by the satellite network, and a step of determining a maximum waiting time based on the satellite coverage information, where the maximum waiting time indicates the maximum period when waiting until the terminal device becomes reachable.

[0023] According to the above solution, the mobility management network element can determine reachability based on the satellite coverage information of the terminal device. If the terminal device is unreachable, the mobility management network element determines a maximum waiting time based on the satellite coverage information to ensure that the terminal device is not paged when it is not covered by the satellite network. This can reduce unnecessary signaling interactions between the mobility management network element and the access network device, and avoid waste of paging resources of the access network device and loss of downlink data of the terminal device.

[0024] In a possible implementation method, based on satellite coverage information, it is determined that the terminal device is unreachable.

[0025] In a possible implementation method, satellite coverage information is received.

[0026] In a possible implementation method, ephemeris information of the satellite cell where the terminal device is located is received, and the satellite coverage information is determined based on the ephemeris information.

[0027] In a possible implementation method, a paging message is sent to the access network device. The paging message includes the identification information of the terminal device, and the paging message indicates that the terminal device is being paged. A first message is received from the access network device. The first message includes a paging failure indication and satellite coverage information. The paging failure indication indicates that the reason for the paging failure is that the terminal device is not covered by the satellite network. Optionally, the paging failure indication further indicates that the mobility management network element needs to perform reachability determination / paging based on the satellite coverage information.

[0028] In a possible implementation method, a paging message is sent to the access network device. The paging message includes the identification information of the terminal device, and the paging message indicates that the terminal device is being paged. A first message is received from the access network device. The first message includes the satellite coverage information of the terminal device. The satellite coverage information indicates that the reason for the paging failure is that the terminal device is not covered by the satellite network. Optionally, the satellite coverage information further indicates that the mobility management network element needs to perform reachability determination / paging based on the satellite coverage information.

[0029] In a possible implementation method, it is determined that the position of the terminal device is fixed, or the movement trajectory of the terminal device is fixed.

[0030] According to a fourth aspect, an embodiment of the present application provides a communication method. The method can be implemented by a terminal device or a module (such as a chip) used by the terminal device. The method includes the step of receiving first information, where the first information indicates that when the terminal device has an uplink transmission requirement, the terminal device performs uplink transmission based on the satellite network coverage status, and when there is an uplink transmission requirement, based on the first information, the step of determining that the terminal device is not covered by the satellite network, and the step of determining to skip performing uplink transmission.

[0031] According to the above solution, when the terminal device is not covered by the satellite network, even if there is an uplink transmission requirement, the terminal device skips performing uplink transmission, so unnecessary network connection operations such as cell scanning and cell selection are avoided, thereby reducing the power consumption of the terminal device.

[0032] In a possible implementation method, the first information is satellite coverage information. The satellite coverage information indicates the time period during which the terminal device is covered by the satellite network and / or the time period during which the terminal device is not covered by the satellite network. The first information clearly indicates that when the terminal device has an uplink transmission requirement, the terminal device starts uplink transmission based on the satellite coverage information.

[0033] In a possible implementation method, satellite coverage information is received. The satellite coverage information indicates a time period during which the terminal device is covered by the satellite network and / or a time period during which the terminal device is not covered by the satellite network. The first information clearly indicates that when the terminal device has uplink transmission requirements, the terminal device starts uplink transmission based on the satellite coverage information.

[0034] In a possible implementation method, the uplink transmission requirements include one or more of periodic TAU, periodic registration, or uplink data transmission.

[0035] According to a fifth aspect, an embodiment of the present application provides a communication method. The method can be implemented by a terminal device or a module (such as a chip) used in the terminal device. The method includes the step of receiving sleep time information, where the sleep time period corresponding to the sleep time information includes a time period during which the terminal device is not covered by the satellite network, the sleep time information is determined based on the satellite coverage information of the terminal device, and the satellite coverage information indicates a time period during which the terminal device is covered by the satellite network and / or a time period during which the terminal device is not covered by the satellite network, and the step of sleeping based on the sleep time information.

[0036] According to the above solution, the terminal device can sleep as much as possible during the time period when the terminal device is not covered by the satellite network, avoid unnecessary network connection operations such as cell scanning and cell selection, and reduce the power consumption of the terminal device.

[0037] In a possible implementation method, the sleep time information includes a sleep start time, and the sleep start time is within the eDRX cycle of the terminal device, the periodic TAU cycle of the terminal device, or the periodic registration cycle of the terminal device.

[0038] In a possible implementation method, the sleep time information includes the sleep start time and the sleep end time, or the sleep time information includes the sleep start time and the sleep period.

[0039] According to a sixth aspect, an embodiment of the present application provides a communication method. The method may be implemented by an access network device or by a module (such as a chip) used by the access network device. The method includes obtaining satellite coverage information or ephemeris information of a satellite cell, where the satellite coverage information indicates a time period during which the satellite cell is covered by a satellite network and / or a time period during which the satellite cell is not covered by the satellite network, and transmitting the satellite coverage information or ephemeris information of the satellite cell to a mobility management network element.

[0040] In a possible implementation method, in the N2 interface setup procedure, satellite coverage information or ephemeris information corresponding to a satellite cell of an access network device is transmitted to a mobility management network element.

[0041] In a possible implementation method, in the registration procedure of a terminal device, satellite coverage information or ephemeris information of a satellite cell where the terminal device is located is transmitted to a mobility management network element.

[0042] In a possible implementation method, a paging message is received from a mobility management network element. The paging message includes the identification information of the terminal device, and the paging message indicates that the terminal device is to be paged. Based on the satellite coverage information of the satellite cell where the terminal device is located, the satellite cell is determined not to have network coverage. A first message is sent to the mobility management network element. The first message includes a paging failure indication and the satellite coverage information of the satellite cell where the terminal device is located. The paging failure indication indicates that the reason for the paging failure is that the satellite cell is not covered by the satellite network. Optionally, the paging failure indication further indicates that the mobility management network element needs to perform reachability determination / paging based on the satellite coverage information.

[0043] In a possible implementation method, a paging message is received from a mobility management network element. The paging message includes the identification information of the terminal device, and the paging message indicates that the terminal device is to be paged. Based on the satellite coverage information of the satellite cell where the terminal device is located, the satellite cell is determined not to have network coverage. A first message is sent to the mobility management network element. The first message includes the satellite coverage information of the satellite cell where the terminal device is located. The satellite coverage information of the satellite cell where the terminal device is located is the satellite coverage information of the terminal device, and the satellite coverage information indicates that the reason for the paging failure is that the satellite cell is not covered by the satellite network. Optionally, the satellite coverage information further indicates that the mobility management network element needs to perform reachability determination / paging based on the satellite coverage information.

[0044] According to a seventh aspect, an embodiment of the present application provides a communication method. The method may be implemented by a mobility management network element or by a module (e.g., a chip) used by the mobility management network element. The method includes determining a periodic TAU cycle of a terminal device based on satellite coverage information of the terminal device and sending the periodic TAU cycle to the terminal device, or determining a periodic registration cycle of the terminal device based on the satellite coverage information of the terminal device and sending the periodic registration cycle to the terminal device, where the satellite coverage information indicates a time period during which the terminal device is covered by a satellite network and / or a time period during which the terminal device is not covered by the satellite network.

[0045] According to the foregoing solution, the mobility management network element determines a periodic TAU cycle or a periodic registration cycle based on the satellite coverage information of the terminal device such that a time period corresponding to the periodic TAU cycle or a time period corresponding to the periodic registration cycle includes a time period during which the terminal device is not covered by the satellite network, ensuring that the terminal device can avoid executing the periodic TAU procedure or the periodic registration procedure as much as possible during the time period when the terminal device is not covered by the satellite network, thereby avoiding unnecessary network connection operations such as cell selection and reducing the power consumption of the terminal device.

[0046] In a possible implementation manner, the time period corresponding to the periodic TAU cycle includes a time period during which the terminal device is not covered by the satellite network, or the time period corresponding to the periodic registration cycle includes a time period during which the terminal device is not covered by the satellite network.

[0047] In a possible implementation method, indication information is sent to an access network device based on satellite coverage information, and the indication information indicates to the access network device to execute a procedure for releasing the terminal device.

[0048] In a possible implementation method, a first period is determined based on the satellite coverage information of the terminal device, and the first period is the period from after the terminal device enters the idle state to before the terminal device enters the sleep state, and the first period is sent to the terminal device.

[0049] In a possible implementation method, a cause value is sent to the terminal device, and the cause value is discontinuous satellite coverage.

[0050] In a possible implementation method, the cause value further indicates to skip performing uplink transmission while the terminal device is in the sleep state.

[0051] In a possible implementation method, a GUTI reallocation command is sent to the terminal device, the GUTI reallocation command includes a periodic TAU cycle, or a TAU acceptance message is sent to the terminal device, and the TAU acceptance message includes a periodic TAU cycle.

[0052] In a possible implementation method, a configuration update command is sent to the terminal device, the configuration update command includes a periodic registration cycle, or a mobility registration update acceptance message is sent to the terminal device, and the mobility registration update acceptance message includes a periodic registration cycle.

[0053] According to an eighth aspect, an embodiment of the present application provides a communication method. The method may be implemented by a terminal device or a module (e.g., a chip) used in the terminal device. The method includes receiving a periodic TAU cycle from a mobility management network element, and performing a periodic TAU based on the periodic TAU cycle, where a time period corresponding to the periodic TAU cycle includes a time period during which the terminal device is not covered by the satellite network, or receiving a periodic registration cycle from a mobility management network element, and performing a periodic registration based on the periodic registration cycle, where a time period corresponding to the periodic registration cycle includes a time period during which the terminal device is not covered by the satellite network.

[0054] According to the foregoing solution, a time period corresponding to a periodic TAU cycle received by the terminal device, or a time period corresponding to a periodic registration cycle received by the terminal device, includes a time period during which the terminal device is not covered by the satellite network, so as to ensure that the terminal device can avoid performing a periodic TAU procedure or a periodic registration procedure as much as possible during the time period when it is not covered by the satellite network, thereby avoiding unnecessary network connection operations such as cell selection and reducing the power consumption of the terminal device.

[0055] In a possible implementation manner, the periodic TAU cycle or the periodic registration cycle is determined based on the satellite coverage information of the terminal device, and the satellite coverage information indicates a time period during which the terminal device is covered by the satellite network and / or a time period during which the terminal device is not covered by the satellite network.

[0056] In a possible implementation method, before a periodic TAU cycle is received from a mobility management network element, a TAU request is sent to the mobility management network element based on the satellite coverage information of the terminal device, or before a periodic registration cycle is received from the mobility management network element, a mobility registration update request is sent to the mobility management network element based on the satellite coverage information of the terminal device, where the satellite coverage information indicates the time period during which the terminal device is covered by the satellite network and / or the time period during which the terminal device is not covered by the satellite network.

[0057] In a possible implementation method, a first period is received from a mobility management network element, where the first period is the period from after the terminal device enters the idle state to before the terminal device enters the sleep state, and the first period is determined based on the satellite coverage information of the terminal device.

[0058] In a possible implementation method, a cause value is received from a mobility management network element, where the cause value is discontinuous satellite coverage.

[0059] In a possible implementation method, the cause value indicates skipping the implementation of uplink transmission when the terminal device is in the sleep state. When there is an uplink transmission requirement, it is determined to skip the implementation of uplink transmission based on the cause value.

[0060] According to a ninth aspect, an embodiment of the present application provides a communication method. The method can be implemented by an access network device or a module (e.g., a chip) used in the access network device. The method includes: based on satellite coverage information of a terminal device, sending a context release request to a mobility management network element, where the context release request is used to request the mobility management network element to release the context of the terminal device, and the satellite coverage information indicates a time period during which the terminal device is covered by a satellite network and / or a time period during which the terminal device is not covered by the satellite network; receiving a periodic TAU cycle from the mobility management network element; and sending the periodic TAU cycle to the terminal device, where a time period corresponding to the periodic TAU cycle includes a time period during which the terminal device is not covered by the satellite network, or receiving a periodic registration cycle from the mobility management network element; and sending the periodic registration cycle to the terminal device, where a time period corresponding to the periodic registration cycle includes a time period during which the terminal device is not covered by the satellite network.

[0061] According to a tenth aspect, an embodiment of the present application provides a communication device. The device may be a mobility management network element or a module (e.g., a chip) used in the mobility management network element. The device has a function of implementing any implementation method of the first aspect to the third aspect and the seventh aspect. The function can be implemented by hardware or by hardware that executes corresponding software. The hardware or software includes one or more modules corresponding to the function.

[0062] According to the 11th aspect, an embodiment of the present application provides a communication device. The device may be a terminal device or a module (e.g., a chip) used in a terminal device. The device has a function of implementing any implementation method of the 4th aspect, the 5th aspect, or the 8th aspect. The function may be implemented by hardware or by hardware that executes corresponding software. The hardware or software includes one or more modules corresponding to the function.

[0063] According to the 12th aspect, an embodiment of the present application provides a communication device. The device may be an access network device or a module (e.g., a chip) used in an access network device. The device has a function of implementing any implementation method of the 6th aspect or the 9th aspect. The function may be implemented by hardware or by hardware that executes corresponding software. The hardware or software includes one or more modules corresponding to the function.

[0064] According to the 13th aspect, an embodiment of the present application provides a communication device including a processor and a memory. The memory is configured to store computer instructions. When the device operates, the processor executes the computer instructions stored in the memory to enable the device to implement any implementation method from the 1st aspect to the 9th aspect.

[0065] According to the 14th aspect, an embodiment of the present application provides a communication device including a unit or means configured to perform the steps of any implementation method from the 1st aspect to the 9th aspect.

[0066] According to the 15th aspect, an embodiment of the present application provides a communication device including a processor and an interface circuit. The processor is configured to communicate with another device via the interface circuit and to implement any implementation method from the 1st aspect to the 9th aspect. There are one or more processors.

[0067] According to the 16th aspect, an embodiment of the present application provides a communication device including a processor coupled to a memory. The processor is configured to call a program stored in the memory to implement any implementation method of the 1st to 9th aspects. The memory may be located inside or outside the device. There may be one or more processors.

[0068] According to the 17th aspect, an embodiment of the present application further provides a computer-readable storage medium. The computer-readable storage medium stores instructions. When the instructions are run on a communication device, any implementation method of the 1st to 9th aspects is implemented.

[0069] According to the 18th aspect, an embodiment of the present application further provides a computer program product. The computer program product includes a computer program or instructions. When the computer program or instructions are run by a communication device, any implementation method of the 1st to 9th aspects is implemented.

[0070] According to the 19th aspect, an embodiment of the present application further provides a chip system including a processor configured to implement any implementation method of the 1st to 6th aspects.

[0071] According to the 20th aspect, an embodiment of the present application further provides a communication system including a mobility management network element and an access network device. The mobility management network element is configured to implement any implementation method of the 1st to 3rd aspects. The access network device is configured to send satellite coverage information of the cell where the terminal device is located to the mobility management network element.

[0072] According to the 21st aspect, embodiments of the present application further provide a communication system including a mobility management network element and an access network device. The mobility management network element is configured to implement any implementation method of the 7th aspect. The access network device is configured to implement any implementation method of the 9th aspect.

Brief Description of the Drawings

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Embodiments for Carrying Out the Invention

[0074] To address the challenges of wireless broadband technology and stay at the forefront of 3rd generation partnership project (3GPP) networks, the 3GPP specification organization has developed the architecture of the next-generation mobile communication system (next-generation system), called the 5th generation (5G) network architecture. The architecture supports access to the 5G core network (CN) using radio access technologies defined by the 3GPP specification organization (such as long term evolution (LTE) access technology or 5G radio access network (RAN) access technology), and also supports access to the core network using non-3GPP access technologies via a non-3GPP interworking function (N3IWF) or a next-generation packet data gateway (ngPDG).

[0075] FIG. 1(a) is a schematic diagram of a 5G network architecture based on a service-based architecture. The 5G network architecture shown in FIG. 1(a) may include a terminal device, an access network device, and a core network device. The terminal device accesses a data network (DN) using the access network device and the core network device. The core network device includes, but is not limited to, some or all of the following network elements: an authentication server function (AUSF) network element (not shown), a unified data management (UDM) network element, a unified data repository (UDR) network element, a network repository function (NRF) network element (not shown), a network exposure function (NEF) network element (not shown), an application function (AF) network element, a policy control function (PCF) network element, an access and mobility management function (AMF) network element, a session management function (SMF) network element, a user plane function (UPF) network element, a binding support function (BSF) network element (not shown), and a network data analysis function (NWDAF) network element (not shown).

[0076] The terminal device may be a user equipment (UE), a mobile station, a mobile terminal, etc. The terminal device can be widely applied to various scenarios such as device-to-device (D2D), vehicle-to-everything (V2X) communication, machine type communication (MTC), internet of things (IoT), virtual reality, augmented reality, industrial control, autonomous driving, telemedicine, smart grid, smart furniture, smart office, smart wearable devices, smart transportation, and smart city. The terminal device may be a mobile phone, a tablet computer, a computer with a wireless transceiver function, a wearable device, a vehicle, an urban air transportation vehicle (such as a drone or a helicopter), a ship, a robot, a robot arm, a smart home device, etc.

[0077] The access network device may be a radio access network (RAN) device or a wireline access network (FAN) device. The radio access network device includes 3GPP access network devices, untrusted non-3GPP access network devices, and trusted non-3GPP access network devices. 3GPP access network devices include, but are not limited to, evolved Node B (eNodeB) of LTE, next generation Node B (gNB) of 5G mobile communication systems, base stations of future mobile communication systems, or modules or units that complete some functions of the base station such as central unit (CU) or distributed unit (DU). Untrusted non-3GPP access network devices include, but are not limited to, untrusted non-3GPP access gateways or N3IWF devices, untrusted wireless local area network (WLAN) access points (APs), switches, and routers. Trusted non-3GPP access network devices include, but are not limited to, trusted non-3GPP access gateways, trusted WLAN APs, switches, and routers. Wireline access network devices include, but are not limited to, wireline access gateways, fixed telephone network devices, switches, and routers.

[0078] The access network device and the terminal device may be in a fixed position or movable. The access network device and the terminal device may be deployed on the ground including indoors or outdoors, or may be handheld or vehicle-mounted, or may be deployed on the water surface, or may be deployed on an airplane, balloon, or a satellite in the sky.

[0079] The AMF network element includes functions such as mobility management and access authentication / authorization. In addition, the AMF network element is further responsible for transmitting user policies between the terminal device and the PCF network element.

[0080] The SMF network element includes functions such as performing session management, executing control policies distributed by the PCF network element, selecting the UPF network element, and allocating the Internet Protocol (IP) address of the terminal device.

[0081] The UPF network element includes functions such as user plane data transfer, session / flow level-based charging statistics, and bandwidth limitation.

[0082] The UDM network element includes functions such as subscription data management and user access authorization.

[0083] The UDR network element includes functions such as storage and retrieval of subscription data, policy data, application data, and other types of data.

[0084] The NEF network element is configured to support capability and event exposure.

[0085] The AF network element transfers application-side requirements to the network side, such as QoS requirements or user equipment status event subscriptions. The AF network element may be a third-party functional entity or an operator-deployed application service, such as an IP Multimedia Subsystem (IMS) voice call service.

[0086] The PCF network element implements policy control functions such as session-level or service flow-level charging, QoS bandwidth guarantee and mobility management, as well as terminal policy determination. The PCF network element includes an access and mobility management policy control function (AM PCF) network element and a session management PCF (SM PCF) network element. The AM PCF network element may provide a mobility management policy, and the SM PCF network element may provide a session management policy.

[0087] The NRF network element may be configured to provide a network element discovery function and to provide network element information corresponding to the network element type based on a request from another network element. The NRF network element further provides network element management services (such as registration, update and deregistration of network elements, as well as subscription and push of network element status).

[0088] The BSF network element may provide functions such as BSF service registration / deregistration / update, connection detection with the NRF network element, session association information creation, terminal device information acquisition, and session association information query for duplicate IP addresses.

[0089] The AUSF network element is responsible for authenticating the user to determine whether the user or device is permitted to access the network.

[0090] The NWDAF network element is mainly configured to collect data (including one or more of terminal device data, access network device data, core network element data, and third-party application data), provide data analysis services based on a machine learning model, and output data analysis results regarding the network, the network management system, and the application for performing policy decisions. The NWDAF network element may be an independent network element or may be located at the same location as another network element. For example, the NWDAF network element is arranged in a PCF network element or an AMF network element.

[0091] The DN is a network outside the carrier network. The carrier network can access multiple DNs. Multiple services may be deployed in the DN, and the DN can provide services such as data services and / or voice services to terminals. For example, the DN is a private network of a smart factory, the sensors installed in the workshop of the smart factory may be terminals, the control server of the sensors is deployed in the DN, and the control server can provide services to the sensors. The sensors can communicate with the control server to obtain the instructions of the control server, and based on the instructions and the like, transmit the collected sensor data to the control server. In another example, the DN is the internal network of a company, the mobile phones or computers of the company's employees may be terminals, and the mobile phones or computers of the employees can access information, data resources, etc. in the company's internal network.

[0092] Npcf, Nufr, Nudm, Naf, Namf, and Nsmf in Figure 1(a) are service-based interfaces provided by PCF, UDR, UDM, AF, AMF, and SMF respectively, and are used to trigger the corresponding service-based operations. N1, N2, N3, N4, and N6 are interface sequence numbers. The meanings of these interface sequence numbers are as follows.

[0093] (1) N1 represents the interface between the AMF and the terminal device, and can be configured to transmit non-access stratum (NAS) signaling (such as QoS rules from the AMF) to the terminal device and the like.

[0094] (2) N2 represents the interface between the AMF and the access network device, and can be configured to transfer radio bearer control information from the core network side to the access network device and the like.

[0095] (3) N3 represents the interface between the access network device and the UPF, and is mainly configured to transmit uplink and downlink user plane data between the access network device and the UPF.

[0096] (4) N4 represents the interface between the SMF and the UPF, and is configured to transfer information between the control plane and the user plane, including the delivery of transfer rules from the control plane to the user plane, QoS control rules, traffic statistics rules, etc., and the reporting of user plane information.

[0097] (5) N6 represents the interface between the UPF and the DN, and is configured to transmit uplink and downlink user data flows between the UPF and the DN.

[0098] Figure 1(b) is a schematic diagram of a 5G network architecture based on point-to-point interfaces. For the description of the functions of the network elements in Figure 1(b), refer to the description of the functions of the corresponding network elements in Figure 1(a). Details will not be described again. The main difference between Figure 1(b) and Figure 1(a) is that the interface between the control plane network elements in Figure 1(a) is a service-based interface, while the interface between the control plane network elements in Figure 1(b) is a point-to-point interface.

[0099] In the architecture shown in FIG. 1(b), the names and functions of the interfaces between network elements are as follows.

[0100] (1) For the meanings of the N1, N2, N3, N4, and N6 interfaces, please refer to the foregoing description.

[0101] (2) N5 represents the interface between the AF and the PCF, and can be configured to deliver application service requests and report network events.

[0102] (3) N7 represents the interface between the PCF and the SMF, and can be configured to deliver protocol data unit (PDU) session granularity control policies and service data flow granularity control policies.

[0103] (4) N8 represents the interface between the AMF and the UDM, and is used by the AMF to obtain subscription data and authentication data related to access and mobility management from the UDM, and can also be used by the AMF to register mobility management related information of the terminal device with the UDM.

[0104] (5) N9 represents the user plane interface between UPFs, and is configured to transmit uplink and downlink user data flows between UPFs.

[0105] (6) N10 represents the interface between the SMF and the UDM, and is used by the SMF to obtain subscription data related to session management from the UDM, and can also be used by the SMF to register session related information of the terminal device with the UDM.

[0106] (7) N11 represents the interface between the SMF and the AMF, and can be configured to transfer control messages sent to the terminal device so as to transfer PDU session tunnel information between the access network device and the UPF, transfer radio resource control information sent to the access network device, and so on.

[0107] (8) N15 represents the interface between the PCF and the AMF, and can be configured to distribute terminal policies and access control related policies.

[0108] (9) N35 represents the interface between the UDM and the UDR, and can be used by the UDM to obtain user subscription data information from the UDR.

[0109] (10) N36 represents the interface between the PCF and the UDR, and can be used by the PCF to obtain policy related subscription data and application data related information from the UDR.

[0110] It may be understood that the aforementioned network elements or functions may be network elements of hardware devices, software functions operating on dedicated hardware, or virtualized functions instantiated on a platform (such as a cloud platform). Optionally, the aforementioned network elements or functions may be implemented by one device, may be implemented by multiple devices, or may be one functional module within one device. This is not particularly limited in the embodiments of the present application.

[0111] In the embodiments of the present application, the mobility management network element may be a mobility management entity (MME) of a 4th generation (4G) network, an AMF network element of a 5G network, or another network element having the functions of an MME or an AMF network element of a future communication system.

[0112] In the embodiments of the present application, the access network device may be an access network device (such as an eNB) of a 4G network, an access network device (such as a gNB) of a 5G network, or another network element having the functions of an access network device of a 4G network or an access network device of a 5G network in a future communication system.

[0113] In the embodiments of the present application, the policy control network element may be a policy and charging rules function (PCRF) network element of a 4G network, a PCF network element of a 5G network, or another network element having the functions of a PCRF network element or a PCF network element in a future communication system.

[0114] In the embodiments of the present application, the storage network element may be a home subscriber server (HSS) of a 4G network, a UDR network element of a 5G network, or another network element having the functions of an HSS or a UDR network element in a future communication system.

[0115] In the embodiments of the present application, the meaning of periodic tracking area update (TAU) and the meaning of periodic registration are the same in the embodiments of the present application. Periodic TAU is a 4G term, and periodic registration is a 5G term.

[0116] In the embodiments of the present application, the periodic TAU cycle may be represented by a periodic TAU timer, and the periodic registration cycle may be represented by a periodic registration timer. The periodic TAU timer is a 4G term, and the periodic registration timer is a 5G term.

[0117] In the embodiments of the present application, the meaning of the detach procedure and the meaning of the deregistration procedure are the same in the embodiments of the present application. The detach procedure is a 4G term, and the deregistration procedure is a 5G term.

[0118] In the embodiments of the present application, the maximum waiting time may be the downlink buffer period of the 4G network, or the maximum waiting time of the 5G network, or another parameter including the downlink buffer period or the maximum waiting time of a future communication system.

[0119] mMTC is one of the important application scenarios of the 5G network, mainly targeted at various Internet of Things (IoT) service applications based on cellular networks, such as maritime / land / railway / air transportation, oil and gas exploration and measurement, environmental monitoring, and mine development. To meet the above requirements, in the 4G era, Narrowband Internet of Things (NB-IoT) and Enhanced Machine Type Communication (eMTC) (also called Long Term Evolution Machine Type Communication (LTE-M)) are defined by 3GPP.

[0120] However, in order to guarantee a wider network coverage and further achieve global coverage without blind spots, low Earth orbit satellites have emerged. Low Earth orbit satellites can assist NB-IoT / eMTC in achieving global IoT coverage and avoid network coverage problems caused by insufficient terrestrial network facilities.

[0121] 5G is used as an example. After entering the idle state, the terminal device in the NB-IoT / eMTC scenario can enter the sleep state. In this case, the terminal device maintains rough synchronization with the AMF on the core network side to ensure that the AMF can sense when the terminal device enters the sleep state. When the downlink data of the terminal device arrives, the UPF notifies the SMF, and then the SMF notifies the AMF. If the AMF finds that the terminal device is still in the sleep state and unreachable, the AMF estimates the maximum waiting time based on the sleep time of the terminal device, returns the maximum waiting time to the SMF, and indicates to the SMF to perform downlink paging after waiting based on the maximum waiting time. In addition, the SMF determines the maximum buffer period based on the maximum waiting time, buffers the downlink data of the terminal device based on the maximum buffer period, and waits until the terminal device becomes reachable.

[0122] There are mainly two power-saving methods for terminal devices: power saving mode (PSM) and extended discontinuous reception (eDRX). PSM means that until there is an uplink service or periodic registration / periodic TAU, the terminal device enters the sleep state after entering the idle state during a time period. eDRX means that when no service is being transmitted, the terminal device enters the sleep state at a fixed time point and wakes up within a specified time to listen for paging information from the network side. In this case, the terminal device is in a reachable state and can receive paging messages from the network side. Unless otherwise specified, the eDRX discussed in this specification refers to eDRX in the idle state.

[0123] In 3GPP, since NB-IoT and eMTC have been introduced into the satellite network architecture, satellites support 4G NB-IoT and eMTC. The 5G satellite architecture has been studied since R16 5G with the aim of harmonizing the 5G architecture with satellites.

[0124] Different from terrestrial coverage, satellite coverage is always moving because the satellite needs to regularly orbit the earth. In the study of the R17 5G satellite architecture, the unique concept of a fixed cell covered on the ground is still used. In other words, although the cell covered by the satellite is moving, the terrestrial access network device maps the cell covered by the satellite to a fixed cell on the ground based on the correspondence between the satellite coverage and the fixed cell on the ground, ensuring that the cell where the terminal device is located and is sensed on the core network side is still a fixed cell on the ground.

[0125] In addition, discontinuous coverage may exist in a specific surface area at the start of satellite deployment or due to deployment costs. For example, in an oilfield mining site located in a desert, when one or more satellites are regularly orbiting the Earth while collecting and reporting data from various sensors for oilfield mining, they may provide network communication services to the oilfield mining site for only a specific time period. In other words, the network communication services provided by the satellite to the terminal devices on the surface have discontinuous coverage. Therefore, the terminal devices are covered by the satellite network during some time periods and not covered by the satellite network during other time periods.

[0126] The discontinuous coverage feature causes the following problems.

[0127] Problem 1: The terminal device may not be covered by the satellite network for a long time. However, the eDRX in the conventional NB-IoT or eMTC scenario has a relatively short sleep time and is therefore impossible to be used in this scenario. In other words, based on the sleep mode of eDRX in the conventional NB-IoT or eMTC scenario, when the terminal device wakes up after the sleep ends, the terminal device may still be in a scenario where it is not covered by the satellite network.

[0128] Problem 2: When the downlink data arrives at the network side, the core network cannot determine whether the terminal device is in an accessible state, and it is difficult to guarantee the success of paging.

[0129] In an embodiment of the present application, the satellite coverage information of the terminal device indicates the time period during which the terminal device is covered by the satellite network and / or the time period during which the terminal device is not covered by the satellite network. For example, the satellite coverage information of the terminal device indicates that the terminal device is not covered by the satellite network from 8:00 am to 9:00 am every day, and / or indicates that the terminal device is covered by the satellite network from 0:00 am to 8:00 am and from 9:00 am to 0:00 am every day. The satellite coverage information of the terminal device may be the satellite coverage information corresponding to the location of the terminal device, or may be the satellite coverage information of the satellite cell where the terminal device is located, or may be the satellite coverage information corresponding to the tracking area (TA) where the terminal device is located. For example, if the terminal device is located in cell 1, the satellite coverage information of the terminal device may be the satellite coverage information of cell 1. As another example, if the terminal device is located in cell 2, the satellite coverage information of the terminal device may be the satellite coverage information of cell 2. Alternatively, the satellite coverage information of the terminal device in the embodiment of the present application may be ephemeris information.

[0130] In an embodiment of the present application, the ephemeris information of a cell is the regularity of the rotation of a satellite corresponding to the cell and orbiting the Earth. For example, the ephemeris information includes satellite orbit plane parameters and satellite parameters such as satellite movement speed, satellite movement direction, distance from the satellite orbit to the Earth's surface, and reference time point. The time period during which the cell is covered by the satellite network and / or the time period during which the cell is not covered by the satellite network can be known based on one or more ephemeris information of the satellite corresponding to the satellite cell. The satellite coverage information of the cell indicates the time period during which the cell is covered by the satellite network and / or the time period during which the cell is not covered by the satellite network. For example, there are three satellite cells under an access network device, namely, satellite cell 1, satellite cell 2, and satellite cell 3. In this case, the N2 setup message includes the identification information of satellite cell 1, the ephemeris information 1 or satellite coverage information 1 corresponding to satellite cell 1, the identification information of satellite cell 2, the ephemeris information 2 or satellite coverage information 2 corresponding to satellite cell 2, the identification information of satellite cell 3, and the ephemeris information 3 or satellite coverage information 3 corresponding to satellite cell 3.

[0131] FIG. 2 is a schematic flowchart of a communication method according to an embodiment of the present application. The method can be used to solve the aforementioned problem 1. The method includes the following steps.

[0132] Step 201: The mobility management network element determines the sleep time information of the terminal device based on the satellite coverage information of the terminal device.

[0133] In the implementation method, after the access network device is powered on, the access network device needs to establish a connection with the mobility management network element. A 5G network is used as an example. The interface is the N2 interface. Therefore, the access network device sends an N2 setup message to the mobility management network element. The N2 setup message may carry the identification information of the satellite cell of the access network device and the ephemeris information or satellite coverage information of the satellite corresponding to each satellite cell. Then, when the terminal device registers with the network, the mobility management network element may obtain information about the satellite cell where the terminal device is located. For example, if the terminal device is located in satellite cell 1 of the access network device, the mobility management network element determines that the satellite coverage information of cell 1 is the satellite coverage information of the terminal device. When the mobility management network element receives the ephemeris information of the satellite corresponding to cell 1 from the access network device, the mobility management network element further needs to first determine the satellite coverage information of cell 1 based on the ephemeris information of the satellite corresponding to cell 1. Optionally, the mobility management network element may further store the satellite coverage information as the satellite coverage information of the terminal device accessing the network from cell 1.

[0134] In another implementation method, as an alternative, in the process of the terminal device registering with the network, the access network device may transmit the ephemeris information or satellite coverage information of the satellite corresponding to the satellite cell where the terminal device is located to the mobility management network element. For example, the terminal device transmits a registration request message to the access network device. After receiving the registration request message, when transmitting the registration request message to the mobility management network element, the access network device further transmits the ephemeris information or satellite coverage information of the satellite corresponding to the satellite cell where the terminal device is located, that is, adds the ephemeris information or satellite coverage information of the satellite corresponding to the satellite cell where the terminal device is located to the first N2 message. When the access network device transmits the ephemeris information of the satellite corresponding to the satellite cell where the terminal device is located, the mobility management network element needs to determine the satellite coverage information of the satellite cell where the terminal device is located based on the ephemeris information. In that case, the mobility management network element uses the satellite coverage information of the cell as the satellite coverage information of the terminal device.

[0135] In another implementation method, a third-party network element, such as an application server outside the core network, a network element dedicated to interacting with satellites, or a network element dedicated to satellite management within the core network, may transmit the ephemeris information or satellite coverage information of the satellite corresponding to the satellite cell where the terminal device is located to the mobility management network element. When the third-party network element transmits the ephemeris information of the satellite corresponding to the satellite cell where the terminal device is located, the mobility management network element needs to determine the satellite coverage information of the satellite cell where the terminal device is located based on the ephemeris information. In that case, the mobility management network element uses the satellite coverage information of the cell as the satellite coverage information of the terminal device.

[0136] The sleep time period corresponding to the sleep time information includes a time period during which the terminal device is not covered by the satellite network.

[0137] In the implementation method, the mobility management network element further determines one or more of the eDRX cycle, periodic TAU cycle, or periodic registration cycle of the terminal device based on satellite coverage information, and the sleep time period corresponding to the sleep time information is included in the sleep time range of the eDRX cycle, periodic TAU cycle, or periodic registration cycle. In this implementation method, the sleep time information in this specification includes the sleep start time, and the sleep start time is within the eDRX cycle, periodic TAU cycle, or periodic registration cycle. Fig. 3(a) is a schematic diagram of the periodic TAU cycle. At the start of the periodic TAU cycle, the terminal device executes the periodic TAU procedure, starts the network connection, and then enters the sleep state from the sleep start time. In addition, the sleep time period of the terminal device within the periodic TAU cycle includes the time period when the terminal device is not covered by the satellite network. Therefore, it is possible to ensure that the terminal device enters the sleep state during the time period when the terminal device is not covered by the satellite network, so that the terminal device does not execute the periodic TAU procedure during the time period without network coverage. This reduces the power consumption of the terminal device. The sleep period is longer than or equal to the period when the terminal device is not covered by the satellite network. See Fig. 3(a). Time point T1 is the sleep start time, time point T2 is the sleep end time, and T2 is also the end time of the TAU cycle. The difference between T2 and T1 is equal to the period when the terminal device is not covered by the satellite network. The sleep time information determined in step 201 is the sleep start time in the example of Fig. 3(a). In the 4G network, the procedure is generally called the periodic TAU procedure, and in the 5G network, the procedure is called the periodic registration procedure. Fig. 3(b) is a schematic diagram of the eDRX cycle. In the paging time window after the start of the eDRX cycle, the terminal device performs listening based on the DRX cycle, and when there is no network connection requirement after the paging time window arrives, the terminal device starts to enter the sleep state at the sleep start time.In addition, the sleep time period of the terminal device during the eDRX cycle includes the time period when the terminal device is not covered by the satellite network. Therefore, it is possible to ensure that the terminal device enters the sleep state during the time period when the terminal device is not covered by the satellite network and does not wake up during the time period when the terminal device is not covered by the satellite network to listen for paging messages. This reduces the power consumption of the terminal device. The sleep period is longer than or equal to the period when the terminal device is not covered by the satellite network. See Figure 3(b). Time point T1 is the sleep start time, time point T2 is the sleep end time, and T2 is also the end time of the eDRX cycle. The difference between T2 and T1 is longer than or equal to the period when the terminal device is not covered by the satellite network. The sleep time information determined in step 201 includes the sleep start time in the example of Figure 3(b).

[0138] In another implementation method, the sleep time information includes a sleep start time and a sleep end time, and the sleep time period between the sleep start time and the sleep end time includes a time period during which the terminal device is not covered by the satellite network. Alternatively, the sleep time information includes a sleep start time and a sleep period, and the sleep end time may be obtained based on the sleep start time and the sleep period. During the sleep time period corresponding to the sleep time information, the terminal device remains in sleep and does not execute services, including skipping the execution of periodic TAU procedures or periodic registration procedures. In the method, the time period indicated by the satellite coverage information of the terminal device and during which the terminal device is not covered by the satellite network is not included in any eDRX cycle or TAU cycle and is a separate sleep time period. Fig. 3(c) is a schematic diagram of the sleep time period. The sleep time information indicates a separate sleep time period. The sleep time period overlaps with the time period during which the terminal device is not covered by the satellite network, or the sleep time period is longer than the time period during which the terminal device is not covered by the satellite network. During the sleep time period, the terminal device enters the sleep state so that it is possible to ensure that the terminal device enters the sleep state during the time period when the terminal device is not covered by the satellite network. This can avoid unnecessary and ineffective network connections and reduce the power consumption of the terminal device. See Fig. 3(c). Time point T1 is the sleep start time, and time point T2 is the sleep end time. The time period between T1 and T2 overlaps with the time period during which the terminal device is not covered by the satellite network, or is longer than the time period during which the terminal device is not covered by the satellite network. Optionally, after the sleep time period, an eDRX cycle is entered. The eDRX cycle can be determined based on existing solutions. The eDRX cycle also has a sleep time period, which may sometimes be referred to as the normal eDRX sleep time period. The sleep time information determined in step 201 includes a sleep start time and a sleep end time in the example of Fig. 3(c).Alternatively, in the example of FIG. 3(c), the sleep time information determined in step 201 includes a sleep start time and a sleep period.

[0139] Step 202: The mobility management network element transmits the sleep time information to the terminal device. Correspondingly, the terminal device receives the sleep time information.

[0140] In an implementation method, the mobility management network element may include the sleep time information in a registration acceptance message transmitted to the terminal device. Optionally, the registration acceptance message further includes one or more of an eDRX cycle, a periodic registration cycle, or a periodic TAU cycle. A 4G network is used as an example, and the sleep time information may be carried in an attach acceptance message or a TAU acceptance message transmitted to the terminal device.

[0141] Step 203: The terminal device sleeps based on the sleep time information.

[0142] Specifically, the terminal device enters a sleep state during a sleep time period corresponding to the sleep time information, and the sleep time period includes a time period when the terminal device is not covered by the satellite network.

[0143] When a deregistration timer (or detachment timer) corresponding to the terminal device expires, the mobility management network element determines, based on the satellite coverage information, that the terminal device is not covered by the satellite network and decides to skip performing deregistration (or detachment) on the terminal device.

[0144] Step 204 is an optional step.

[0145] Skipping to perform deregistration on the terminal device may also be understood as maintaining the registration state of the terminal device without change. Skipping to perform detachment on the terminal device may also be understood as maintaining the attachment state of the terminal device without change.

[0146] In a 4G network, when the detach timer (or implicit detach timer) corresponding to the terminal device expires, if the mobility management network element, i.e., the MME, determines based on the satellite coverage information that the terminal device is not covered by the satellite network, the mobility management network element decides to skip performing a detachment on the terminal device, that is, to maintain the current mobility management state of the terminal device as an attachment state or an EMM registered state (EPS Mobility Management-Registered, EMM-Registered). If the mobility management network element determines based on the satellite coverage information that the terminal device is covered by the satellite network, the mobility management network element decides to perform a detachment on the terminal device, that is, to change the current mobility management state of the terminal device to a detached state or an EMM deregistered state. According to this solution, when the terminal device is not covered by the satellite network, the mobility management network element does not execute the detachment procedure on the terminal device, so the switching of the status of the terminal device going back and forth between attachment and detachment or between registration and deregistration is reduced, thereby reducing the signaling interaction between the terminal device and the network and reducing the power consumption of the terminal device. This is because the power consumption of the terminal device is low when the terminal device is not covered by the satellite network. When the mobility management network element detaches the terminal device, the terminal device needs to be re-attached after subsequently being covered by the satellite network. As a result, more signaling interactions are caused and the power consumption of the terminal device increases.

[0147] In a 5G network, when the deregistration timer (or implicit detach timer) corresponding to a terminal device expires, if the mobility management network element, i.e., the AMF, determines based on satellite coverage information that the terminal device is not covered by the satellite network, the mobility management network element decides to skip performing deregistration on the terminal device. If the mobility management network element determines based on satellite coverage information that the terminal device is covered by the satellite network, the mobility management network element decides to skip performing registration on the terminal device, i.e., to keep the terminal device in the current registered state. According to this solution, when the terminal device is not covered by the satellite network, the mobility management network element does not deregister the terminal device, so the switching of the status of the terminal device going back and forth between registration and deregistration is reduced, thereby reducing the signaling interaction between the terminal device and the network and reducing the power consumption of the terminal device. This is because the power consumption of the terminal device is low when the terminal device is not covered by the satellite network. When the mobility management network element deregisters the terminal device, the terminal device needs to be re-registered after being subsequently covered by the satellite network. As a result, more signaling interactions are caused and the power consumption of the terminal device increases.

[0148] According to the above solution, the mobility management network element determines sleep time information based on the satellite coverage information of the terminal device, and the sleep time period corresponding to the sleep time information includes the time period when the terminal device is not covered by the satellite network, so that the terminal device can sleep as much as possible during the time period when it is not covered by the satellite network, avoid unnecessary network connection operations such as cell scanning and cell selection, and ensure that the power consumption of the terminal device can be reduced.

[0149] Figure 4 is a schematic flowchart of a communication method according to an embodiment of the present application. The method can be used to solve the aforementioned problem 1. The method includes the following steps.

[0150] Step 401: When the deregistration timer (or detach timer) corresponding to the terminal device expires, the mobility management network element determines that the terminal device is not covered by the satellite network based on the satellite coverage information of the terminal device.

[0151] For the implementation method for the mobility management network element to determine the satellite coverage information of the terminal device, refer to the description of step 201. Details will not be described again.

[0152] The deregistration timer may also be an implicit deregistration timer. This is not limited in this specification. The detach timer may also be an implicit detach timer. This is not limited in this specification.

[0153] Step 402: The mobility management network element determines to skip performing deregistration (or detachment) on the terminal device.

[0154] Skipping performing deregistration on the terminal device may also be understood as maintaining the registration state of the terminal device unchanged. Skipping performing detachment on the terminal device may also be understood as maintaining the attachment state of the terminal device unchanged, that is, always keeping the terminal device in the EMM registration state. Optionally, when the terminal device is not deregistered, it responds to the case where the terminal device is not covered by the satellite network.

[0155] In a 4G network, when the detach timer corresponding to a terminal device expires, if the mobility management network element, i.e., the MME, determines based on satellite coverage information that the terminal device is not covered by the satellite network, the mobility management network element decides to skip performing a detachment on the terminal device, that is, to maintain the current mobility management state of the terminal device as an attachment state or an EMM registration state. If the mobility management network element determines based on satellite coverage information that the terminal device is covered by the satellite network, the mobility management network element decides to perform a detachment on the terminal device, that is, to change the current mobility management state of the terminal device to a detached state or an EMM deregistration state. According to this solution, when the terminal device is not covered by the satellite network, the mobility management network element does not execute a detachment procedure on the terminal device, so the switching of the status of the terminal device going back and forth between attachment and detachment is reduced, thereby reducing the signaling interaction between the terminal device and the network and reducing the power consumption of the terminal device. This is because the power consumption of the terminal device is low when the terminal device is not covered by the satellite network. When the mobility management network element detaches the terminal device, the terminal device needs to be reattached after subsequently being covered by the satellite network. As a result, more signaling interactions are caused and the power consumption of the terminal device increases.

[0156] In a 5G network, when the deregistration timer corresponding to a terminal device expires, if the mobility management network element, i.e., the AMF, determines based on satellite coverage information that the terminal device is not covered by the satellite network, the mobility management network element decides to skip performing deregistration on the terminal device. If the mobility management network element determines based on satellite coverage information that the terminal device is covered by the satellite network, the mobility management network element decides to skip performing registration on the terminal device, that is, to keep the terminal device in the current registered state. According to this solution, when the terminal device is not covered by the satellite network, the mobility management network element does not deregister the terminal device, so the switching of the status of the terminal device going back and forth between registration and deregistration is reduced, thereby reducing the signaling interaction between the terminal device and the network and reducing the power consumption of the terminal device. This is because when the terminal device is not covered by the satellite network, the power consumption of the terminal device is low. When the mobility management network element deregisters the terminal device, the terminal device needs to be re-registered after being subsequently covered by the satellite network. As a result, more signaling interactions are caused and the power consumption of the terminal device increases.

[0157] According to the above solution, since the switching of the status of the terminal device going back and forth between registration and deregistration or between attachment and detachment is reduced, it is possible to reduce the signaling interaction between the terminal device and the network and it is possible to reduce the power consumption of the terminal device.

[0158] In the implementation method, after step 402, the following steps 403 and 404 may be further implemented.

[0159] Step 403: The mobility management network element transmits the first information to the terminal device. Correspondingly, the terminal device receives the first information.

[0160] The first information indicates that when the terminal device has uplink transmission requirements, the terminal device performs uplink transmission based on the satellite network coverage status.

[0161] Step 404: When there are uplink transmission requirements, if the terminal device determines based on the first information that it is not covered by the satellite network, the terminal device decides to skip performing uplink transmission.

[0162] The uplink transmission requirements in this specification include, but are not limited to, one or more of periodic TAU, periodic registration, or uplink data transmission.

[0163] In the implementation method, the first information is the satellite coverage information of the terminal device described in step 401. The mobility management network element transmits the satellite coverage information of the terminal device to the terminal device to indicate to the terminal device to perform uplink transmission based on the satellite coverage information when the terminal device has uplink transmission requirements. Therefore, when the terminal device has uplink transmission requirements, it is determined based on the satellite coverage information whether the terminal device is currently covered by the satellite network. If the terminal device is not covered by the satellite network, it is determined to skip performing uplink transmission. If the terminal device is covered by the satellite network, it is determined to perform uplink transmission.

[0164] In another implementation method, the first piece of information is indication information, and the indication information clearly indicates that when the terminal device has uplink transmission requirements, it checks the satellite network coverage status and performs uplink transmission based on the satellite network coverage status. Therefore, when the terminal device has uplink transmission requirements, the terminal device first checks whether it is currently covered by the satellite network. If the terminal device is not covered by the satellite network, it is determined to skip performing uplink transmission. If the terminal device is covered by the satellite network, it is determined to perform uplink transmission.

[0165] In another implementation method, in step 403, when transmitting the first piece of information to the terminal device, the mobility management network element further transmits the satellite coverage information of the terminal device to the terminal device. In this case, in this specification, the first piece of information is indication information, and the indication information clearly indicates that when the terminal device has uplink transmission requirements, it performs uplink transmission based on the satellite coverage information. Therefore, when the terminal device has uplink transmission requirements, the terminal device determines whether it is covered by the satellite network based on the satellite coverage information. If the terminal device is not covered by the satellite network, it is determined to skip performing uplink transmission. If the terminal device is covered by the satellite network, it is determined to perform uplink transmission.

[0166] According to the solutions of step 403 and step 404, when the terminal device is not covered by the satellite network, even if there are uplink transmission requirements, the terminal device skips performing uplink transmission, so unnecessary and ineffective network connection operations such as cell scanning and cell selection are avoided, thereby reducing the power consumption of the terminal device.

[0167] Figure 5 is a schematic flowchart of a communication method according to an embodiment of the present application. The method can be used to solve the aforementioned problem 2. The method includes the following steps.

[0168] Step 501: A mobility management network element determines satellite coverage information of a terminal device.

[0169] In an implementation method, the mobility management network element may determine the satellite coverage information of the terminal device according to the method described in step 201.

[0170] In another implementation method, alternatively, the mobility management network element may determine the satellite coverage information of the terminal device by using the following method. The mobility management network element sends a paging message to an access network device, the paging message includes identification information of the terminal device in the idle state, and the paging message indicates that the terminal device is to be paged. In that case, the access network device pages the terminal device. If the access network device determines that the cell where the terminal device is located is not currently covered by the satellite network, the access network device fails in paging. Therefore, the access network device sends a first message to the mobility management network element. The first message includes a paging failure indication and satellite coverage information of the satellite cell where the terminal device is located. The paging failure indication indicates that the reason for this paging failure is that the terminal device is not covered by the satellite network. Optionally, the paging failure indication further indicates that the mobility management network element needs to perform reachability determination / paging based on the satellite coverage information. The satellite coverage information of the satellite cell where the terminal device is located is the satellite coverage information of the terminal device.

[0171] In another implementation method, the mobility management network element may alternatively determine the satellite coverage information of the terminal device using the following method. The mobility management network element sends a paging message to the access network device. The paging message includes the identification information of the terminal device in the idle state, and the paging message indicates that the terminal device is to be paged. In that case, the access network device pages the terminal device. If the access network device determines that the cell where the terminal device is located is not currently covered by the satellite network, the access network device fails to page. Therefore, the access network device sends a first message to the mobility management network element. The first message includes the satellite coverage information of the satellite cell where the terminal device is located. The satellite coverage information of the satellite cell where the terminal device is located is the satellite coverage information of the terminal device. In addition, the satellite coverage information indicates that the reason for this paging failure is that the terminal device is not covered by the satellite network. Optionally, the satellite coverage information may further indicate that the mobility management network element needs to perform reachability determination / paging based on the satellite coverage information.

[0172] In the implementation method, when the mobility management network element is a 5G AMF network element, the AMF network element may perform step 501 after receiving a downlink data arrival notification from the SMF network element. In other words, the downlink data arrival notification triggers the mobility management network element to perform step 501.

[0173] In the implementation method, when the mobility management network element is a 4G MME, the MME may perform step 501 after determining that downlink data of the user plane needs to be transmitted.

[0174] Step 502: The mobility management network element determines a maximum waiting time based on satellite coverage information, where the maximum waiting time indicates the maximum period when the terminal device waits until it becomes reachable.

[0175] The maximum waiting time in this specification needs to cover the time period when the terminal device is not covered by the satellite network, or it is understood that after reaching the maximum waiting time, the terminal device should be covered by the satellite network. The maximum waiting time may be the 4G downlink buffer period or the 5G maximum waiting period.

[0176] Optionally, before step 502, the mobility management network element further determines that the terminal device is unreachable based on satellite coverage information.

[0177] In a 4G network, the mobility management network element is the MME. After determining the maximum waiting time, the MME determines the expiration period of the downlink data buffer based on the maximum waiting time, which may indicate whether the data of the terminal device is currently buffered on the core network side. After the expiration period of the downlink data buffer expires, the MME determines that there is no current downlink buffer data for the terminal device. In a 4G network, the maximum waiting time is sometimes also called the downlink data buffer time.

[0178] In a 5G network, the mobility management network element is the AMF network element. After determining the maximum waiting time, the AMF network element may send the maximum waiting time to the SMF network element. Next, the SMF network element may determine the extended buffer time based on the maximum waiting time. The extended buffer time indicates a specific period during which the user plane network element buffers downlink data. After the extended buffer time is reached and the buffered data has not yet been sent to the terminal device, the SMF discards the corresponding buffered data. In a 5G network, the maximum waiting time may also be referred to as the estimated maximum waiting time.

[0179] According to the foregoing solution, the mobility management network element may determine reachability based on the satellite coverage information of the terminal device. If the terminal device is unreachable, the mobility management network element determines the maximum waiting time based on the satellite coverage information to ensure that the terminal device is not paged when it is not covered by the satellite network and that downlink data is not sent to the terminal device. This reduces the power consumption of the mobility management network element and reduces data loss.

[0180] In the implementation method, before step 201, step 401, and / or step 501, the mobility management network element further determines that the position of the terminal device is fixed or the movement trajectory of the terminal device is fixed. Alternatively, it is understood that the mobility management network element determines that the terminal device is a terminal device at a fixed position or a terminal device with a fixed movement trajectory. For example, the mobility management network element may obtain the subscription information of the terminal device and determine, based on the subscription information of the terminal device, that the position of the terminal device is fixed or the movement trajectory of the terminal device is fixed. In other words, the mobility management network element implements the solution of the embodiments corresponding to FIGS. 2, 4, and / or 5 only for terminal devices with fixed positions or fixed movement trajectories. The fixed movement trajectory may be understood as that the terminal device has specific mobility, but the movement trajectory of the terminal device is predictable and the network side can sense the geographical location of the terminal device.

[0181] Hereinafter, the foregoing solution will be described with reference to specific examples. The following solution is applicable to future communication networks such as 4G networks, 5G networks, or 6G networks.

[0182] FIG. 6 is a schematic flowchart of a communication method according to an embodiment of the present application. This solution is a specific implementation of the embodiment corresponding to FIG. 2.

[0183] The method includes the following steps.

[0184] Step 601: The access network device sends an N2 setup message to the mobility management network element. Correspondingly, the mobility management network element receives the N2 setup message.

[0185] After the access network device is powered on, N2 setup messages are sent in the procedure to establish an N2 interface between the access network device and the mobility management network element. If the current network is a 4G network, the N2 interface corresponds to the S1-MME interface of the 4G network.

[0186] Optionally, the N2 setup message includes the identification information of the satellite cells of the access network device and the ephemeris information or satellite coverage information of the satellites corresponding to each satellite cell.

[0187] Step 602: The terminal device sends a registration request message to the access network device. Correspondingly, the access network device receives the registration request message.

[0188] The registration request message is used to request registration to the network.

[0189] The registration request message may be a registration request message in a 5G network, or an attach message or a TAU request message in a 4G network.

[0190] Step 603: The access network device sends the registration request message and access network (AN) parameters to the mobility management network element. Correspondingly, the mobility management network element receives the registration request message and AN parameters. The registration request message is carried by a NAS message sent by the terminal device to the mobility management network element. The AN parameters are added by the access network device to the first N2 message and sent to the mobility management network element side together with the registration request message.

[0191] If the N2 setup message in step 601 does not transmit the identification information of the satellite cell of the access network device and the ephemeris information or satellite coverage information corresponding to each satellite cell, in the subsequent registration procedure of the terminal device, the AN parameters added by the access network device may include the ephemeris information or satellite coverage information corresponding to the satellite cell where the terminal device is located.

[0192] Step 604: The mobility management network element determines that the location or movement trajectory of the terminal device is fixed.

[0193] Alternatively, it is understood that the mobility management network element determines that the terminal device is a terminal device at a fixed location or a terminal device with a fixed movement trajectory.

[0194] In the implementation method, the mobility management network element may obtain the subscription information of the terminal device and determine, based on the subscription information of the terminal device, that the location of the terminal device is fixed or the movement trajectory of the terminal device is fixed.

[0195] Step 604 is an optional step.

[0196] Step 605: The mobility management network element determines the sleep start time of the terminal device and one or more of the periodic TAU cycle, periodic registration cycle, or eDRX cycle based on the ephemeris information or satellite coverage information corresponding to the satellite cell where the terminal device is located.

[0197] When the mobility management network element receives the ephemeris information corresponding to the satellite cell where the terminal device is located from the access network device, the mobility management network element determines the satellite coverage information corresponding to the satellite cell where the terminal device is located based on the ephemeris information corresponding to the satellite cell where the terminal device is located.

[0198] The periodic TAU corresponds to the periodic registration procedure in the 5G network and the periodic TAU procedure in the 4G network.

[0199] The satellite coverage information corresponding to the satellite cell where the terminal device is located is the satellite coverage information of the terminal device.

[0200] In the implementation method, the time period indicated by the satellite coverage information of the terminal device and not covered by the satellite network by the terminal device is included in the periodic registration cycle, or it is understood that the sleep time period during the periodic registration cycle includes the time period indicated by the satellite coverage information of the terminal device and not covered by the satellite network by the terminal device. For a specific example of the implementation method, please refer to Figure 3(a).

[0201] In the implementation method, the time period indicated by the satellite coverage information of the terminal device and not covered by the satellite network by the terminal device is included in the eDRX cycle, or it is understood that the sleep time period during the eDRX cycle includes the time period indicated by the satellite coverage information of the terminal device and not covered by the satellite network by the terminal device. For a specific example of the implementation method, please refer to Figure 3(b).

[0202] Step 606: Other steps of the registration procedure.

[0203] Step 607: The mobility management network element sends a non-access stratum (NAS) message to the terminal device. Correspondingly, the terminal device receives the NAS message.

[0204] The NAS message includes the sleep start time and further includes one or more of the periodic TAU cycle, the eDRX cycle, or the periodic registration cycle.

[0205] In the implementation method, the NAS message includes a registration acceptance message, an attach acceptance message, or a TAU acceptance message. The message includes a sleep start time and further includes one or more of a periodic registration cycle, a periodic TAU cycle, or an eDRX cycle.

[0206] Step 608: The terminal device sleeps during the periodic TAU cycle, the periodic registration cycle, or the eDRX cycle based on the sleep start time.

[0207] In the implementation method, the terminal device enters the sleep state from the sleep start time during the periodic TAU cycle and ends the sleep state when the periodic TAU cycle ends. The sleep time period of the terminal device includes the time period when the terminal device is not covered by the satellite network. For example, the terminal device may sleep according to the method shown in FIG. 3(a).

[0208] In the implementation method, the terminal device enters the sleep state from the sleep start time during the eDRX cycle and ends the sleep state when the eDRX cycle ends. The sleep time period of the terminal device includes the time period when the terminal device is not covered by the satellite network. For example, the terminal device may sleep according to the method shown in FIG. 3(b).

[0209] According to the above solution, in the registration process of the terminal device, the mobility management network element determines the sleep start time and one or more of the eDRX cycle, the periodic TAU cycle, or the periodic registration cycle based on the ephemeris information or satellite coverage information corresponding to the cell and provided by the access network device, and ensures that the terminal device sleeps as much as possible during the time period when the terminal device is not covered by the satellite network, avoids unnecessary network connection operations such as cell scanning and cell selection, and can reduce the power consumption of the terminal device.

[0210] Figure 7 is a schematic flowchart of a communication method according to an embodiment of the present application. This solution is a specific implementation of the embodiment corresponding to FIG. 2. The method includes the following steps.

[0211] Steps 701 to 704 are the same as steps 601 to 604.

[0212] Step 704 is an optional step.

[0213] Step 705: The mobility management network element determines the sleep time information of the terminal device based on the ephemeris information or satellite coverage information corresponding to the satellite cell where the terminal device is located.

[0214] When the mobility management network element receives the ephemeris information corresponding to the satellite cell where the terminal device is located from the access network device, the mobility management network element determines the satellite coverage information corresponding to the satellite cell where the terminal device is located based on the ephemeris information corresponding to the satellite cell where the terminal device is located. The satellite coverage information corresponding to the satellite cell where the terminal device is located is the satellite coverage information of the terminal device.

[0215] In the implementation method, the sleep time information includes a sleep start time and a sleep end time, and the sleep time period between the sleep start time and the sleep end time is a time period during which the terminal device is not covered by the satellite network.

[0216] In the implementation method, the sleep time information includes a sleep start time and a sleep end time, and the sleep time period between the sleep start time and the sleep end time includes a time period during which the terminal device is not covered by the satellite network. In other words, the sleep time period indicated by the sleep start time and the sleep end time is longer than the time period during which the terminal device is not covered by the satellite network.

[0217] In another implementation method, the sleep time information includes a sleep start time and a sleep period, and the sleep end time can be obtained based on the sleep start time and the sleep period.

[0218] During the sleep time period corresponding to the sleep time information, the terminal device maintains sleep and does not execute services even if periodic TAU, periodic registration, or transmission of uplink data to be transmitted is not performed.

[0219] Optionally, the mobility management network element may determine one or more of an eDRX cycle, a periodic TAU cycle, or a periodic registration cycle based on service information and according to existing methods during the time period when the terminal device is covered by the satellite network.

[0220] In the implementation method, the time period indicated by the satellite coverage information of the terminal device and not covered by the satellite network for the terminal device is not included in any eDRX cycle, periodic TAU cycle, or periodic registration cycle, and is a separate sleep time period.

[0221] Step 706: Other steps of the registration procedure.

[0222] Step 707: The mobility management network element sends an NAS message to the terminal device. Correspondingly, the terminal device receives the NAS message.

[0223] The NAS message includes sleep time information. Optionally, the NAS message further includes one or more of an eDRX cycle, a periodic TAU cycle, or a periodic registration cycle.

[0224] In the implementation method, the NAS message includes a registration acceptance message, an attach acceptance message, or a TAU acceptance message. The message includes sleep time information. Optionally, the registration acceptance message further includes one or more of an eDRX cycle, a periodic TAU cycle, or a periodic registration cycle.

[0225] Step 708: The terminal device sleeps based on the sleep time information.

[0226] The terminal device sleeps during the sleep time period indicated by the sleep time information without performing periodic TAU, periodic registration, or transmission of uplink data to be transmitted, and the service is not executed.

[0227] Optionally, after the sleep time period indicated by the sleep time information, the terminal device enters the coverage of the satellite network. In this case, the terminal device may sleep based on an eDRX cycle, a periodic TAU cycle, or a periodic registration cycle.

[0228] Step 709: When the deregistration timer (or detach timer) corresponding to the terminal device expires, the mobility management network element determines whether to perform deregistration (or detachment) on the terminal device based on the sleep time information of the terminal device.

[0229] After the mobility management network element determines that the deregistration timer (or detach timer) corresponding to the terminal device has expired, the mobility management network element determines whether the terminal device is currently in a sleep time period corresponding to the case where the terminal device is not covered by the satellite network based on the sleep time information of the terminal device. If the terminal device is currently in a sleep time period corresponding to the case where the terminal device is not covered by the satellite network, the mobility management network element determines to skip performing deregistration (or detachment) for the terminal device. If the terminal device is not currently in a sleep time period corresponding to the case where the terminal device is not covered by the satellite network, the mobility management network element determines to perform deregistration (or detachment) for the terminal device.

[0230] Step 709 is an optional step.

[0231] In the above embodiment, in the registration process of the terminal device, the mobility management network element determines the sleep time information based on the ephemeris information or satellite coverage information corresponding to the satellite cell and provided by the access network device, so that the terminal device sleeps as much as possible during the time period when the terminal device is not covered by the satellite network, avoids unnecessary network connection operations such as cell selection, and guarantees that the power consumption of the terminal device can be reduced.

[0232] In the implementation method, the embodiment corresponding to FIG. 7 can be applied to a scenario where the terminal device is not covered by the satellite network for a long time. A new power-saving mode is introduced. In other words, during the time period when the terminal device is not covered by the satellite network, the terminal device is always in sleep and skips performing any services, including periodic TAU, periodic registration, or uplink data transmission. This can avoid unnecessary and ineffective network connection operations such as cell scan and cell selection, and can minimize the power consumption of the terminal device.

[0233] FIG. 8 is a schematic flowchart of a communication method according to an embodiment of the present application. This solution is a specific implementation of the embodiment corresponding to FIG. 4.

[0234] The method includes the following steps.

[0235] Steps 801 to 804 are the same as steps 601 to 604.

[0236] Step 804 is an optional step.

[0237] Step 805: The mobility management network element determines the satellite coverage information of the terminal device.

[0238] When the mobility management network element receives the ephemeris information corresponding to the satellite cell where the terminal device is located from the access network device, the mobility management network element determines the satellite coverage information corresponding to the satellite cell where the terminal device is located based on the ephemeris information corresponding to the satellite cell where the terminal device is located. The satellite coverage information corresponding to the satellite cell where the terminal device is located is the satellite coverage information of the terminal device.

[0239] When the mobility management network element receives satellite coverage information corresponding to the satellite cell where the terminal device is located from the access network device, the satellite coverage information corresponding to the satellite cell where the terminal device is located is the satellite coverage information of the terminal device.

[0240] Optionally, the mobility management network element may determine an eDRX cycle, a periodic TAU cycle, or a periodic registration cycle according to an existing method.

[0241] Step 806: Other steps of the registration procedure.

[0242] Step 807: The mobility management network element sends an NAS message to the terminal device. Correspondingly, the terminal device receives the NAS message.

[0243] The NAS message includes indication information and the satellite coverage information of the terminal device. Optionally, the NAS message further includes one or more of an eDRX cycle, a periodic TAU cycle, or a periodic registration cycle. The indication information indicates to the terminal device to start a periodic TAU procedure, a periodic registration procedure, or uplink data transmission based on the satellite coverage information of the terminal device when the periodic TAU timer or the periodic registration timer expires, or when there is uplink data transmission.

[0244] In the implementation method, the NAS message includes a registration acceptance message, an attach acceptance message, or a TAU acceptance message. The message includes indication information and the satellite coverage information of the terminal device. Optionally, the message further includes one or more of an eDRX cycle, a periodic TAU cycle, or a periodic registration cycle.

[0245] Step 808: The terminal device determines whether to initiate a periodic TAU, periodic registration, or uplink data transmission based on the indication information and the satellite coverage information of the terminal device.

[0246] Specifically, based on the indication information and the satellite coverage information of the terminal device, it is determined whether the terminal device is covered by the satellite network, that is, whether the terminal device is currently covered by the satellite network. When the terminal device is covered by the satellite network, the terminal device initiates a periodic TAU, periodic registration, or uplink data transmission. When the terminal device is not covered by the satellite network, the terminal device does not initiate a periodic TAU, periodic registration, or uplink data transmission.

[0247] Step 809: The mobility management network element determines whether to perform deregistration (or detachment) for the terminal device based on the indication information and satellite coverage information of the terminal device.

[0248] Specifically, when the deregistration timer (or detachment timer) corresponding to the terminal device expires, it is determined whether to perform deregistration (or detachment) for the terminal device based on the satellite coverage information of the terminal device. When the terminal device is covered by the satellite network, the mobility management network element performs deregistration (or detachment) for the terminal device. When the terminal device is not covered by the satellite network, the mobility management network element skips performing deregistration (or detachment) for the terminal device.

[0249] In the foregoing embodiments, in the registration process, attach process, or TAU process of the terminal device, the mobility management network element determines the satellite coverage information of the terminal device, and indicates to the terminal device to perform periodic TAU, periodic registration, or uplink data transmission based on the satellite coverage information. This can prevent the terminal device from performing periodic TAU, periodic registration, or uplink data transmission within a time range not covered by the satellite network, avoid unnecessary network connection operations such as cell scanning and cell selection, and reduce the power consumption of the terminal device. In addition, when the terminal device is in a time range not covered by the satellite network, it can also be avoided that the terminal device is deregistered (or detached) by the network side.

[0250] In the implementation method, the embodiment corresponding to FIG. 8 can be applied to a scenario where the terminal device is not covered by the satellite network for a long time. This is because there is a limit value for the cycle time of periodic TAU or periodic registration, and it may not be very large. Therefore, when the period during which the terminal device is not covered by the satellite network is long, it is inevitable that periodic TAU or periodic registration needs to be performed. In this case, since the terminal device is not covered by the satellite network and the terminal device continuously performs cell scanning and cell selection, the power consumption loss increases. In addition, since the network side does not receive periodic TAU or periodic registration from the terminal device, the terminal device is deregistered or detached. Therefore, in order to avoid unnecessary periodic TAU or periodic registration when the idle terminal device is not covered by the satellite network, in the embodiment corresponding to FIG. 8, when the terminal device is not covered by the satellite network, the terminal device does not perform periodic TAU or periodic registration and uplink data transmission, and the mobility management network element on the network side does not perform deregistration (or detachment) on the terminal device, so the signaling interaction between the terminal device and the mobility management network element can be reduced to the maximum extent, and the power consumption of the terminal device is reduced.

[0251] FIG. 9 is a schematic flowchart of a communication method according to an embodiment of the present application. This solution is a specific implementation of the embodiment corresponding to FIG. 4.

[0252] The method includes the following steps.

[0253] Steps 901 to 906 are the same as steps 801 to 806.

[0254] Step 907: The mobility management network element sends an NAS message to the terminal device. Correspondingly, the terminal device receives the NAS message.

[0255] The NAS message includes indication information. Optionally, the NAS message further includes one or more of an eDRX cycle, a periodic TAU cycle, or a periodic registration cycle. The indication information indicates to the terminal device to detect whether the terminal device is covered by the satellite network when the periodic TAU timer or the periodic registration timer expires, or when there is uplink data transmission.

[0256] In an implementation method, the NAS message includes a registration acceptance message, an attach acceptance message, or a TAU acceptance message. The message includes indication information. Optionally, the registration acceptance message further includes an eDRX cycle and / or a TAU cycle.

[0257] Step 908: The terminal device determines whether to initiate a periodic TAU, a periodic registration, or an uplink data transmission based on the indication information.

[0258] Specifically, based on the indication information, it is determined whether the terminal device is covered by the satellite network, that is, whether the terminal device is currently covered by the satellite network. When the terminal device is covered by the satellite network, the terminal device initiates a periodic TAU, a periodic registration, or an uplink data transmission. When the terminal device is not covered by the satellite network, the terminal device does not initiate a periodic TAU, a periodic registration, or an uplink data transmission.

[0259] Step 909 is the same as step 809.

[0260] In the foregoing embodiment, in the registration process of the terminal device, the mobility management network element indicates to the terminal device to perform periodic TAU, periodic registration, or uplink data transmission based on whether the terminal device is covered by the satellite network. This can prevent the terminal device from performing periodic TAU, periodic registration, or uplink data transmission within a time range when the terminal device is not covered by the satellite network, avoid unnecessary network connection operations such as cell scan and cell selection, and reduce the power consumption of the terminal device. In addition, when the terminal device is in a time range not covered by the satellite network, it can also be avoided that the terminal device is deregistered (or detached) by the network side.

[0261] In the implementation method, the embodiment corresponding to FIG. 9 can be applied to a scenario where the terminal device is not covered by the satellite network for a long time. This is because there is a limit value for the cycle time of periodic TAU or periodic registration, and it may not be very large. Therefore, when the period during which the terminal device is not covered by the satellite network is long, it is inevitably necessary to perform periodic TAU or periodic registration. In this case, since the terminal device is not covered by the satellite network and the terminal device continuously performs network connection operations such as cell scanning and cell selection, the power consumption loss increases. In addition, since the network side does not receive a periodic TAU request or a periodic registration request from the terminal device, the terminal device is deregistered or detached. Therefore, in order to avoid unnecessary periodic TAU or periodic registration when the idle terminal device is not covered by the satellite network, in the embodiment corresponding to FIG. 9, when the terminal device is not covered by the satellite network, the terminal device does not perform periodic TAU or periodic registration and uplink data transmission, and the mobility management network element on the network side does not perform deregistration (or detachment) on the terminal device, so the signaling interaction between the terminal device and the mobility management network element can be reduced to the maximum extent, and the power consumption of the terminal device is reduced.

[0262] FIG. 10 is a schematic flowchart of a communication method according to an embodiment of the present application. This solution is a specific implementation of the embodiment corresponding to FIG. 5.

[0263] The method includes the following steps.

[0264] Step 1001 is the same as step 601.

[0265] Step 1002: After the terminal device enters the idle state, the access network device sends an N2 message to the mobility management network element. Correspondingly, the mobility management network element receives the N2 message.

[0266] If the N2 setup message in Step 1001 does not carry the identification information of the satellite cell of the access network device and the ephemeris information or satellite coverage information corresponding to each satellite cell, the N2 message may include the ephemeris information or satellite coverage information corresponding to the satellite cell where the terminal device is located. Optionally, the N2 message may further include the identification information of the satellite cell where the terminal device is located. The satellite cell where the terminal device is located may be understood as the satellite cell that was last accessed by the terminal device before the terminal device entered the idle state. Specifically, the N2 message may be an N2 release message, corresponding to the S1 release message of the 4G network.

[0267] Step 1003 is the same as Step 604.

[0268] Step 1003 is an optional step.

[0269] Step 1004: The mobility management network element determines whether the terminal device is reachable.

[0270] In the implementation method, the mobility management network element determines whether the terminal device is reachable based on the satellite coverage information of the terminal device. If the terminal device is not currently covered by the satellite network, the terminal device is unreachable. If the terminal device is currently covered by the satellite network, whether the terminal device is reachable is determined based on an existing solution, for example, based on the power-saving sleep state of the terminal device. The satellite coverage information of the terminal device is the satellite coverage information of the satellite cell where the terminal device is located.

[0271] In the implementation method, the mobility management network element determines whether the terminal device is reachable based on the satellite coverage information of the terminal device and the eDRX cycle, the periodic TAU cycle, or the periodic registration cycle. If the terminal device is not currently covered by the satellite network, or if the terminal device is in the sleep time of the eDRX cycle, or if the terminal device is in the sleep time of the periodic TAU cycle, or if the terminal device is in the sleep time of the periodic registration cycle, the terminal device is unreachable. If the terminal device is currently covered by the satellite network, the terminal device is not in the sleep time of the eDRX cycle, the terminal device is not in the sleep time of the periodic TAU cycle, and the terminal device is not in the sleep time of the periodic registration cycle, the terminal device is reachable. It should be understood that the sleep time of the periodic TAU cycle or the periodic registration cycle is the sleep time period during which the terminal device enters the sleep state after a time period after the terminal device enters the idle state from the connected state, for example, from the power saving mode (PSM) of the 4G network or the mobile initiated connection only (MICO) mode of the 5G network.

[0272] Step 1005: If the terminal device is unreachable, the mobility management network element determines the maximum waiting time based on the satellite coverage information of the terminal device.

[0273] For the specific implementation of this step, refer to the description of Step 502.

[0274] Step 1006: When the terminal device enters the reachable state, the mobility management network element sends a paging message to the access network device. Correspondingly, the access network device receives the paging message.

[0275] The paging message includes the identification information of the terminal device and the identification information of the paging cell.

[0276] The paging cell may be the cell last accessed by the terminal device, or may be all cells within the tracking area where the cell last accessed by the terminal device is located.

[0277] Step 1007: The access network device pages the terminal device.

[0278] According to the above solution, the mobility management network element can determine the reachability based on the satellite coverage information of the terminal device. If the terminal device is unreachable, the mobility management network element determines the maximum waiting time based on the satellite coverage information to ensure that the terminal device is not paged and downlink data is not sent to the terminal device when it is not covered by the satellite network. This reduces the power consumption of the mobility management network element and reduces data loss.

[0279] In the implementation method, when the mobility management network element of this solution is a 4G MME, before step 1004, the MME may further receive a downlink data arrival notification from the user plane network element, and the downlink data arrival notification triggers the MME to perform step 1004. In addition, after step 1005, the MME further determines the downlink data buffer expiration period based on the maximum waiting time or the downlink buffer time to indicate whether the data of the terminal device is currently buffered on the core network side. After the downlink data buffer expiration period expires, the MME determines that there is no current downlink buffer data for the terminal device.

[0280] In the implementation method, when the mobility management network element of this solution is a 5G AMF network element, before step 1004, the AMF network element may further receive a downlink data arrival notification from the SMF network element, and the downlink data arrival notification triggers the AMF network element to perform step 1004. In addition, after step 1005, the AMF network element further indicates to the SMF network element and / or the user plane network element to buffer the data based on the maximum waiting time. Next, the SMF network element may determine an extended buffer time based on the maximum waiting time. The extended buffer time indicates a specific period during which the user plane network element buffers the downlink data. After the extended buffer time is reached and the buffered data has not yet been transmitted to the terminal device, the SMF network element discards the corresponding buffered data.

[0281] FIG. 11 is a schematic flowchart of a communication method according to an embodiment of the present application. This solution is a specific implementation of the embodiment corresponding to FIG. 5.

[0282] The method includes the following steps.

[0283] Step 1101: The mobility management network element sends a paging message to the access network device. Correspondingly, the access network device receives the paging message.

[0284] The paging message includes the identification information of the terminal device and the identification information of the paging cell.

[0285] The paging cell may be the cell last accessed by the terminal device, or may be all cells within the tracking area where the cell last accessed by the terminal device is located.

[0286] Step 1102: The access network device determines that the satellite cell where the terminal device is located is not covered by the satellite network.

[0287] In the implementation method, the access network device determines whether the terminal device is covered by the satellite network based on the satellite coverage information of the terminal device. If the terminal device is not currently covered by the satellite network, paging fails. If the terminal device is currently covered by the satellite network, the terminal device is paged. The satellite coverage information of the terminal device is the satellite coverage information of the satellite cell where the terminal device is located.

[0288] Step 1103: The access network device sends a first message to the mobility management network element. Correspondingly, the mobility management network element receives the first message.

[0289] Specifically, the first message can be an N2 message or a paging failure message.

[0290] The access network device determines that the terminal device is not currently covered by the satellite network. Therefore, the access network device sends a first message to the mobility management network element. The first message includes a paging failure indication and the satellite coverage information of the terminal device. The paging failure indication indicates that the reason for this paging failure is that the terminal device is not covered by the satellite network. Optionally, the paging failure indication further indicates that the mobility management network element needs to perform reachability determination / paging based on the satellite coverage information.

[0291] In another implementation method, the access network device determines that the terminal device is not currently covered by the satellite network. Therefore, the access network device sends a first message to the mobility management network element. The first message includes the satellite coverage information of the terminal device. The satellite coverage information indicates that the reason for this paging failure is that the terminal device is not covered by the satellite network. Optionally, the satellite coverage information further indicates that the mobility management network element needs to perform reachability determination / paging based on the satellite coverage information.

[0292] Step 1104: The mobility management network element determines the maximum waiting time based on the satellite coverage information of the terminal device.

[0293] For the specific implementation of this step, please refer to the description of Step 502.

[0294] Steps 1105 and 1106 are the same as Steps 1006 and 1007.

[0295] According to the foregoing solution, when a mobility management network element notifies an access network device to page a terminal device, the access network device determines whether the terminal device can be paged currently based on the satellite coverage information of the terminal device. If the terminal device is not within the coverage of the satellite network, the access network device notifies the mobility management network element that the paging has failed, and transmits the satellite coverage information of the terminal device to the mobility management network element. Thereby, the mobility management network element determines the maximum waiting time based on the satellite coverage information thereof, and ensures that the terminal device is not paged when it is not covered by the satellite network. This can reduce unnecessary signaling interactions between the mobility management network element and the access network device, and avoid waste of paging resources of the access network device and loss of downlink data of the terminal device.

[0296] In the implementation method, when the mobility management network element of this solution is a 4G MME, before step 1101, the MME may further receive a downlink data arrival notification from a user plane network element, and the downlink data arrival notification triggers the MME to perform step 1101. In addition, after step 1104, the MME further determines a downlink data buffer expiration period based on the maximum waiting time, that is, the downlink buffer time, to indicate whether the data of the terminal device is currently buffered on the core network side. After the downlink data buffer expiration period expires, the MME determines that there is currently no downlink buffer data of the terminal device.

[0297] In the implementation method, when the mobility management network element of this solution is a 5G AMF network element, before step 1101, the AMF network element may further receive a downlink data arrival notification from the SMF network element, and the downlink data arrival notification triggers the AMF network element to perform step 1101. In addition, after step 1104, the AMF network element further instructs the SMF network element and / or the user plane network element to buffer data based on the maximum waiting time. Next, the SMF network element may determine an extended buffer time based on the maximum waiting time. The extended buffer time indicates a specific period during which the user plane network element buffers downlink data. After the extended buffer time is reached and the buffered data has not yet been transmitted to the terminal device, the SMF network element discards the corresponding buffered data.

[0298] In the embodiments corresponding to FIG. 12 and the embodiments corresponding to FIG. 14, a mobility management network element determines an appropriate periodic TAU cycle or a periodic registration cycle, whereby a terminal device skips performing uplink signaling or uplink data transmission during a time period when the terminal device is not covered by the satellite network based on the periodic TAU cycle or the periodic registration cycle. This example is used for explanation. In actual applications, the mobility management network element may determine another parameter (for example, a service gap or eDRX), whereby the terminal device skips performing uplink signaling or uplink data transmission during a time period when the terminal device is not covered by the satellite network based on that other parameter. It may be understood that the "periodic TAU cycle" and the "periodic registration cycle" in the embodiments corresponding to FIG. 12 and the embodiments corresponding to FIG. 14 may be replaced by another parameter (such as a service gap or eDRX). For the definition of the service gap, refer to TS23.401 V17.2.0. The "another parameter" may be a parameter indicating a period.

[0299] FIG. 12 is a schematic flowchart of a communication method according to an embodiment of the present application. For example, in a 4G application scenario, the mobility management network element and the access network device may be an MME and an eNB, respectively. For example, in a 5G application scenario, the mobility management network element and the access network device may be an AMF and a gNB, respectively. The terminal device in this embodiment is a terminal device of a satellite access type.

[0300] The method includes the following steps.

[0301] Step 1201: The mobility management network element determines a periodic TAU cycle or a periodic registration cycle based on the satellite coverage information of the terminal device.

[0302] Optionally, the position of the terminal device is fixed, or the movement trajectory of the terminal device is fixed.

[0303] For the meaning of satellite coverage information, please refer to the previous description. Details will not be described again in this specification.

[0304] Optionally, when determining that the terminal device is a satellite access type terminal device, the mobility management network element may determine a periodic TAU cycle or a periodic registration cycle based on the satellite coverage information of the terminal device.

[0305] In 4G, the mobility management network element is the MME, and the MME determines the periodic TAU cycle. In a specific implementation, the periodic TAU cycle may be represented by a periodic TAU timer. In 5G, the mobility management network element is the AMF, and the AMF determines the periodic registration cycle. In a specific implementation, the periodic registration cycle may be represented by a periodic registration timer.

[0306] In order to skip the terminal device from performing a periodic TAU procedure or a periodic registration procedure and ensure that the terminal device remains in the sleep state when the terminal device is not covered by the satellite network, that is, from the time when the terminal device enters the idle state until the time before the periodic TAU timer or the periodic registration timer expires, to ensure that the time period corresponding to the periodic TAU cycle includes the time period when the terminal device is not covered by the satellite network, or the time period corresponding to the periodic registration cycle includes the time period when the terminal device is not covered by the satellite network.

[0307] The following describes different implementation methods for triggering the mobility management network element to perform step 1201.

[0308] Method 1: Based on the satellite coverage information of the terminal device, the mobility management network element determines that the terminal device is likely to be out of the satellite network coverage and sends indication information to the access network device. The indication information indicates to the access network device to execute the terminal device connection release procedure. Next, the access network device sends a UE context release request to the mobility management network element. The UE context release request is used to request the mobility management network element to release the context of the terminal device. After receiving the UE context release request, the mobility management network element is triggered to perform step 1201.

[0309] Method 2: Based on the satellite coverage information of the terminal device, the access network device determines that the terminal device is likely to be out of the satellite network coverage and triggers the access network device to send a context release request to the mobility management network element. The context release request is used to request the mobility management network element to release the context of the terminal device. After receiving the UE context release request, the mobility management network element is triggered to perform step 1201.

[0310] Method 3: Based on the satellite coverage information of the terminal device, the terminal device determines that the terminal device is likely to be out of the satellite network coverage and sends a TAU request or a mobility registration update request to the mobility management network element. After receiving the TAU request or the mobility registration update request, the mobility management network element is triggered to perform step 1201.

[0311] Optionally, the mobility management network element further determines a first period based on the satellite coverage information of the terminal device. The first period is the period from when the terminal device enters the idle state until it enters the sleep state. The first period may also be referred to as the period during which the terminal device is in the active state (active time). When the terminal device is in the active state, the network can call the terminal device from the idle state to the connected state by paging.

[0312] Step 1202: The mobility management network element sends a periodic TAU cycle or a periodic registration cycle to the terminal device.

[0313] In 4G, a mobility management network element, such as an MME, sends a periodic TAU cycle to the terminal device. Optionally, the MME sends a GUTI Reallocation Command to the terminal device, and the GUTI Reallocation Command carries the periodic TAU cycle. Alternatively, the MME sends a TAU acceptance message to the terminal device, and the TAU acceptance message carries the periodic TAU cycle.

[0314] In 5G, a mobility management network element, such as an AMF, sends a periodic registration cycle to the terminal device. Optionally, the AMF sends a UE Configuration Update Command to the terminal device, and the UE configuration update command carries the periodic registration cycle. Alternatively, the AMF sends a mobility registration update acceptance message to the terminal device, and the mobility registration update acceptance message carries the periodic registration cycle.

[0315] In the implementation method, the mobility management network element uses the access network device to send a periodic TAU cycle or a periodic registration cycle to the terminal device. In other words, the mobility management network element sends a periodic TAU cycle or a periodic registration cycle to the access network device, and then the access network device sends the periodic TAU cycle or the periodic registration cycle to the terminal device.

[0316] Optionally, the mobility management network element may further send a first period to the terminal device. The first period is the period from after the terminal device enters the idle state until before the terminal device enters the sleep state. The first period may also be referred to as the period (active time) during which the terminal device is in the active state. When the terminal device is in the active state, the network may call the terminal device from the idle state to the connected state by paging.

[0317] Optionally, the mobility management network element may further send a cause value to the terminal device, where the cause value is discontinuous satellite coverage, or the cause value indicates skipping the implementation of uplink transmission while the terminal device is in sleep.

[0318] Step 1203: The terminal device performs a periodic TAU based on the periodic TAU cycle or performs a periodic registration based on the periodic registration cycle.

[0319] Figure 13(a) is a schematic diagram of a periodic TAU cycle or a periodic registration cycle according to an embodiment of the present application. The start point of the periodic TAU cycle (i.e., the periodic TAU timer) or the periodic registration cycle (i.e., the periodic registration timer) may be the point in time when the terminal device enters the idle state. The time period corresponding to the periodic TAU cycle or the time period corresponding to the periodic registration cycle includes the time period during which the terminal device is not covered by the satellite network. The terminal device enters the sleep state during the time period when the terminal device is not covered by the satellite network.

[0320] Figure 13(b) is another schematic diagram of a periodic TAU cycle or a periodic registration cycle according to an embodiment of the present application. The start point of the periodic TAU cycle (i.e., the periodic TAU timer) or the periodic registration cycle (i.e., the periodic registration timer) may be the point in time when the terminal device enters the idle state. The time period corresponding to the periodic TAU cycle or the time period corresponding to the periodic registration cycle includes the time period during which the terminal device is not covered by the satellite network. The time period corresponding to the periodic TAU cycle or the time period corresponding to the periodic registration cycle further includes a first period, and the terminal device can be activated by the network side via paging within the first period and enter the connection mode. The terminal device enters the sleep state during the time period when the terminal device is not covered by the satellite network.

[0321] Optionally, if the terminal device receives a cause value and the cause value indicates skipping the terminal device from performing uplink transmission during sleep, when there is an uplink transmission requirement, the terminal device skips performing uplink transmission based on the cause value during the time period corresponding to the periodic TAU cycle or the periodic registration cycle.

[0322] According to the foregoing solution, the mobility management network element determines a periodic TAU cycle or a periodic registration cycle based on the satellite coverage information of the terminal device such that the time period corresponding to the periodic TAU cycle or the time period corresponding to the periodic registration cycle includes the time period during which the terminal device is not covered by the satellite network, ensuring that the terminal device can avoid performing the periodic TAU procedure or the periodic registration procedure as much as possible during the time period when the terminal device is not covered by the satellite network, thereby avoiding unnecessary network connection operations such as cell selection and reducing the power consumption of the terminal device.

[0323] FIG. 14 is a schematic flowchart of a communication method according to an embodiment of the present application. This solution is a specific implementation of the embodiment corresponding to FIG. 12. For example, in a 4G application scenario, the mobility management network element and the access network device may be an MME and an eNB, respectively. For example, in a 5G application scenario, the mobility management network element and the access network device may be an AMF and a gNB, respectively. The terminal device in this embodiment is a terminal device of a satellite access type.

[0324] The method includes the following steps.

[0325] Step 1401: The mobility management network element determines that the terminal device is likely to be out of the satellite network coverage based on the satellite coverage information of the terminal device, and sends indication information to the access network device. Correspondingly, the access network device receives the indication information.

[0326] Optionally, the position of the terminal device is fixed, or the movement trajectory of the terminal device is fixed.

[0327] In an implementation method, a mobility management network element may receive satellite coverage information of a terminal device from an access network device, a third party, or the terminal device. In another implementation method, the mobility management network element receives cell ephemeris information from an access network device, a third party, or the terminal device, and may then determine the satellite coverage information of the terminal device based on the cell ephemeris information.

[0328] The indication information indicates to the access network device to execute a procedure for releasing the terminal device. In 4G, the procedure for releasing the terminal device is the S1 release procedure. In 5G, the procedure for releasing the terminal device is the procedure for releasing the access network (AN).

[0329] Step 1401 is an optional step.

[0330] Step 1402: The access network device sends a UE context release request to the mobility management network element. Correspondingly, the mobility management network element receives the UE context release request.

[0331] The UE context release request is used to request the mobility management network element to release the UE context so that the mobility management network element can release the connection to the terminal device and allow the terminal device to enter the idle state.

[0332] In an implementation method, when step 1401 is performed, the indication information triggers the access network device to perform step 1402.

[0333] In another implementation method, when step 1401 is not implemented, the access network device may determine that the terminal device is likely to be out of satellite network coverage based on the satellite coverage information of the terminal device, and then trigger the access network device to perform step 1402.

[0334] In another implementation method, when step 1401 is not implemented, the access network device may trigger the access network device to perform step 1402 based on another reason. Another reason in this specification includes, but is not limited to, that the service is not being executed on the terminal device, operator operations and maintenance system intervention (O&M Intervention), or unspecified failure.

[0335] Optionally, in 4G, after receiving a UE context release request, the mobility management network element (i.e., MME) may further request the serving gateway (S-GW) to release the bearer resources. Optionally, in 5G, after receiving a UE context release request, the mobility management network element (i.e., AMF) may further request the SMF to release the bearer resources.

[0336] Step 1403: The mobility management network element determines a periodic TAU cycle or a periodic registration cycle based on the satellite coverage information of the terminal device.

[0337] Optionally, when it is determined that the terminal device is a terminal device of the satellite access type, the mobility management network element may determine a periodic TAU cycle or a periodic registration cycle based on the satellite coverage information of the terminal device.

[0338] In 4G, the mobility management network element is the MME, and the MME determines the periodic TAU cycle. In a specific implementation, the periodic TAU cycle can be represented by a periodic TAU timer. In 5G, the mobility management network element is the AMF, and the AMF determines the periodic registration cycle. In a specific implementation, the periodic registration cycle can be represented by a periodic registration timer.

[0339] To skip the terminal device from performing the periodic TAU procedure or the periodic registration procedure when the terminal device is not covered by the satellite network, and to ensure that the terminal device remains in the sleep state, in other words, to ensure that the time period from when the terminal device enters the idle state until before the periodic TAU timer or the periodic registration timer expires includes the time period when the terminal device is not covered by the satellite network, the time period corresponding to the periodic TAU cycle includes the time period when the terminal device is not covered by the satellite network, or the time period corresponding to the periodic registration cycle includes the time period when the terminal device is not covered by the satellite network.

[0340] Optionally, the mobility management network element further determines a first period. The first period is the period from when the terminal device enters the idle state until before the terminal device enters the sleep state. The first period may also be referred to as the period when the terminal device is in the active state (active time). When the terminal device is in the active state, the network can call the terminal device from the idle state to the connected state by paging.

[0341] Step 1404: The mobility management network element sends a reallocation command to the terminal device, and the reallocation command includes a periodic TAU cycle or a periodic registration cycle. Correspondingly, the terminal device receives the reallocation command.

[0342] Optionally, the reallocation command further includes the period during which the terminal device is in an active state.

[0343] Optionally, the reallocation command further includes a cause value, which is discontinuous satellite coverage. Optionally, the cause value further indicates skipping the uplink transmission when the terminal device is in sleep. The uplink transmission in this specification includes uplink service data transmission and / or uplink signaling transmission.

[0344] Step 1405: The terminal device sends a reallocation response to the mobility management network element. Correspondingly, the mobility management network element receives the reallocation response.

[0345] In 4G, the reallocation command may be a GUTI reallocation command. The GUTI reallocation command includes a periodic TAU cycle and optionally further includes a first period and / or a cause value. The reallocation response may be a GUTI reallocation completion message.

[0346] In 4G, the reallocation command may be a UE configuration update command. The UE configuration update command includes a periodic registration cycle and optionally further includes a first period and / or a cause value. The reallocation response may be a UE configuration update completion message.

[0347] Steps 1404 and 1405 are optional steps.

[0348] Step 1406: The mobility management network element sends a UE context release command to the access network device. Correspondingly, the access network device receives the UE context release command.

[0349] The UE context release command indicates to the access network device to release the UE context.

[0350] If Steps 1404 and 1405 are not performed, the UE context release command includes a periodic TAU cycle or a periodic registration cycle, and optionally further includes a first period and / or a cause value.

[0351] Step 1407: The access network device sends an RRC connection release request to the terminal device. Correspondingly, the terminal device receives the RRC connection release request.

[0352] If the UE context release command includes a periodic TAU cycle or a periodic registration cycle, the RRC connection release request includes the periodic TAU cycle or the periodic registration cycle. If the UE context release command further includes a first period and / or a cause value, the RRC connection release request further includes the first period and / or the cause value.

[0353] Step 1408: The access network device sends a UE context release completion message to the mobility management network element. Correspondingly, the mobility management network element receives the UE context release completion message.

[0354] Step 1408 is an optional step.

[0355] Step 1409: The terminal device skips performing uplink transmission during the time period corresponding to the periodic TAU cycle or the periodic registration cycle based on the cause value.

[0356] In other words, when there is an uplink transmission requirement, the terminal device skips performing uplink transmission during the time period corresponding to the periodic TAU cycle or the periodic registration cycle based on the cause value.

[0357] Step 1409 is an optional step.

[0358] When step 1404 or step 1407 includes a cause value, step 1409 is performed.

[0359] According to the foregoing solution, in the procedure of releasing the terminal device, when the terminal device enters the idle state, the update of the periodic TAU cycle or the periodic registration cycle is triggered, and after entering the idle state, the terminal device sleeps during the time period when the terminal device is not covered by the satellite network, and it is guaranteed that the power consumption of the terminal device is reduced.

[0360] FIG. 15 is a schematic flowchart of a communication method according to an embodiment of the present application. This solution is a specific implementation of the embodiment corresponding to FIG. 12. For example, in a 4G application scenario, the mobility management network element and the access network device may be an MME and an eNB, respectively. For example, in a 5G application scenario, the mobility management network element and the access network device may be an AMF and a gNB, respectively.

[0361] The method includes the following steps.

[0362] Step 1501: Based on the satellite coverage information of the terminal device, the terminal device determines that the terminal device is likely to be out of the satellite network coverage, and uses the access network device to send a TAU request or a Mobility Registration Update request to the mobility management network element. Correspondingly, the mobility management network element receives the TAU request or the mobility registration update request.

[0363] Optionally, the position of the terminal device is fixed, or the movement trajectory of the terminal device is fixed.

[0364] In an implementation method, the terminal device may receive satellite coverage information of the terminal device from an access network device, a third party, or a core network device. In another implementation method, the terminal device may receive cell ephemeris information from an access network device, a third party, or a core network device, and then determine the satellite coverage information of the terminal device based on the cell ephemeris information.

[0365] In 4G, the access network device sends a TAU request to the mobility management network element (i.e., MME). In 5G, the access network device sends a mobility registration update request to the mobility management network element (i.e., AMF).

[0366] Step 1502 is the same as step 1403.

[0367] Step 1503: The mobility management network element sends a TAU acceptance message or a mobility registration update acceptance message to the terminal device by using the access network device, where the TAU acceptance message includes a periodic TAU cycle, or the mobility registration update acceptance message includes a periodic registration cycle. Correspondingly, the terminal device receives the TAU acceptance message or the mobility registration update acceptance message.

[0368] In 4G, the access network device sends a TAU request to the mobility management network element (i.e., MME). Correspondingly, the MME sends a TAU acceptance message to the access network device. In 5G, the access network device sends a mobility registration update request to the mobility management network element (i.e., AMF). Correspondingly, the AMF sends a mobility registration update acceptance message to the access network device.

[0369] Optionally, the TAU acceptance message or the mobility registration update acceptance message further includes a first period. For the meaning of the first period, refer to the description of step 1403.

[0370] Optionally, the TAU acceptance message or the mobility registration update acceptance message further includes a cause value. For the meaning of the cause value, refer to the description of step 1403.

[0371] Step 1504: The terminal device skips performing an uplink transmission during a time period corresponding to a periodic TAU cycle or a periodic registration cycle based on the cause value.

[0372] In other words, when there is an uplink transmission requirement, the terminal device skips performing an uplink transmission during a time period corresponding to a periodic TAU cycle or a periodic registration cycle based on the cause value.

[0373] Step 1504 is an optional step. When step 1503 includes a cause value, step 1504 is performed.

[0374] According to the above solution, before the terminal device is likely to move out of the satellite network coverage, the terminal device triggers a periodic TAU procedure or a periodic registration procedure, so the mobility management network element determines a periodic TAU cycle or a periodic registration cycle based on the satellite coverage information of the terminal device. The time period corresponding to the periodic TAU cycle or the periodic registration cycle includes the time period during which the terminal device is not covered by the satellite network after entering the idle state, in order to ensure that the terminal device sleeps during this time period and thereby reduces the power consumption of the terminal device.

[0375] Figure 16(a) is a schematic flowchart of a communication method according to an embodiment of the present application. This solution is a specific implementation of the embodiment corresponding to FIG. 4. The method includes the following steps.

[0376] Step 1601a: The terminal device obtains the satellite coverage information of the terminal device.

[0377] Optionally, the position of the terminal device is fixed, or the movement trajectory of the terminal device is fixed.

[0378] In an implementation method, the terminal device may receive the satellite coverage information of the terminal device from an access network device, a third party, or a core network device (for example, a mobility management network element). In another implementation method, the terminal device receives the ephemeris information from an access network device, a third party, or a core network device, and then may determine the satellite coverage information of the terminal device based on the ephemeris information.

[0379] The terminal device receiving the satellite coverage information or the ephemeris information of the terminal device from the access network device may be implemented using the following method. The terminal device receives an RRC message from the access network device, and the RRC message includes the satellite coverage information or the ephemeris information of the terminal device. The RRC message may be an RRC reconfiguration message or a broadcast message.

[0380] The terminal device receiving satellite coverage information or ephemeris information of the terminal device from a mobility management network element can be implemented using the following method. The terminal device receives an NAS message from the mobility management network element, and the NAS message includes the satellite coverage information or ephemeris information of the terminal device. Optionally, the NAS message further includes one or more of an eDRX cycle, a periodic TAU cycle, or a periodic registration cycle. The NAS message may be a registration acceptance message, an attach acceptance message, or a TAU acceptance message.

[0381] The satellite coverage information of the terminal device may be ephemeris information.

[0382] Step 1602a: The terminal device determines whether to initiate a periodic TAU, a periodic registration, or an uplink data transmission based on the satellite coverage information of the terminal device.

[0383] Specifically, the terminal device determines whether the terminal device is covered by the satellite network based on the satellite coverage information of the terminal device, that is, whether the terminal device is currently covered by the satellite network. When the terminal device is covered by the satellite network, the terminal device initiates a periodic TAU, a periodic registration, or an uplink data transmission. When the terminal device is not covered by the satellite network, the terminal device does not initiate a periodic TAU, a periodic registration, or an uplink data transmission.

[0384] In the implementation method, the terminal device may further receive indication information from an access network device or a mobility management network element. The indication information instructs the terminal device to check the satellite network coverage status when the terminal device has uplink transmission requirements, and perform uplink transmission based on the satellite network coverage status. The uplink transmission requirements in this specification include, but are not limited to, one or more of periodic TAU, periodic registration, or uplink data transmission. When the terminal device receives the indication information, step 1602a may be as follows. The terminal device determines whether to initiate periodic TAU, periodic registration, or uplink data transmission based on the satellite coverage information of the terminal device and the indication information. When the terminal device is covered by the satellite network, the terminal device initiates periodic TAU, periodic registration, or uplink data transmission. When the terminal device is not covered by the satellite network, the terminal device does not initiate periodic TAU, periodic registration, or uplink data transmission.

[0385] According to the foregoing solution, when the terminal device is not covered by the satellite network, even if there are uplink transmission requirements, the terminal device skips performing uplink transmission, thereby avoiding unnecessary and ineffective network connection operations such as cell scanning and cell selection, and reducing the power consumption of the terminal device.

[0386] Optionally, the embodiment corresponding to FIG. 16(a) can be applied to a scenario where the terminal device is not covered by the satellite network for a long time. This is because there is a limit value for the cycle time of periodic TAU or periodic registration, and it may not be very large. Therefore, when the period during which the terminal device is not covered by the satellite network is long, it is inevitable that periodic TAU or periodic registration needs to be performed. In this case, since the terminal device is not covered by the satellite network and the terminal device continuously performs cell scanning and cell selection, the power consumption loss increases. Therefore, in order to avoid unnecessary periodic TAU or periodic registration when the idle terminal device is not covered by the satellite network, in the embodiment corresponding to FIG. 16(a), when the terminal device is not covered by the satellite network, the terminal device does not perform periodic TAU or periodic registration and uplink data transmission, so the signaling interaction between the terminal device and the mobility management network element can be reduced to the maximum extent, and the power consumption of the terminal device is reduced.

[0387] FIG. 16(b) is a schematic flowchart of a communication method according to an embodiment of the present application. This solution is a specific implementation of the embodiment corresponding to FIG. 4. The method includes the following steps.

[0388] Step 1601b: The mobility management network element obtains the satellite coverage information of the terminal device.

[0389] In the implementation method, the mobility management network element may receive the satellite coverage information of the terminal device from the terminal device, the access network device, or a third party, and the satellite coverage information of the terminal device may be ephemeris information.

[0390] In another implementation method, the mobility management network element may receive ephemeris information from a terminal device, an access network device, or a third party, and then determine the satellite coverage information of the terminal device based on the ephemeris information.

[0391] Step 1602b: The mobility management network element determines whether to perform deregistration (or detachment) for the terminal device based on the satellite coverage information of the terminal device.

[0392] Specifically, when the deregistration timer (or detachment timer) corresponding to the terminal device expires, it is determined whether to perform deregistration (or detachment) for the terminal device based on the satellite coverage information of the terminal device. When the terminal device is covered by the satellite network, the mobility management network element performs deregistration (or detachment) for the terminal device. When the terminal device is not covered by the satellite network, the mobility management network element skips performing deregistration (or detachment) for the terminal device.

[0393] Skipping performing deregistration for the terminal device may also be understood as maintaining the registration state of the terminal device unchanged. Skipping performing detachment for the terminal device may also be understood as maintaining the attachment state of the terminal device unchanged, that is, always keeping the terminal device in the EMM registration state. Optionally, when the terminal device is not deregistered, it responds to the case where the terminal device is not covered by the satellite network.

[0394] According to the foregoing solution, since the switching of the status of the terminal device going back and forth between registration and deregistration or between attachment and detachment is reduced, it is possible to reduce the signaling interaction between the terminal device and the network, and it is possible to reduce the power consumption of the terminal device.

[0395] In the implementation method, the embodiment corresponding to FIG. 16(a) and the embodiment corresponding to FIG. 16(b) can be combined for implementation.

[0396] In order to implement the functions in the foregoing embodiments, the mobility management network element, the access network device, or the terminal device may be understood to include corresponding hardware structures and / or software modules for implementing the functions. A person skilled in the art should easily recognize that, with respect to the combination with the units and method steps in the examples described in the embodiments disclosed in this application, this application can be implemented using hardware or a combination of hardware and computer software. Whether the function is implemented using hardware or using hardware driven by computer software depends on the specific application scenario and the design constraints of the technical solution.

[0397] Each of FIG. 17 and FIG. 18 is a schematic diagram of the structure of a possible communication device according to an embodiment of the present application. These communication devices may be configured to implement the functions of the mobility management network element, the access network device, or the terminal device in the foregoing method embodiments, and thus, the beneficial effects of the foregoing method embodiments can also be achieved. In the embodiments of the present application, the communication device may be a mobility management network element, an access network device, or a terminal device, or may be a module (for example, a chip) applied to a mobility management network element, an access network device, or a terminal device.

[0398] As shown in FIG. 17, the communication device 1700 includes a processing unit 1710 and a transceiver unit 1720. The communication device 1700 is configured to implement the functions of the mobility management network element, access network device, or terminal device in the foregoing method embodiments.

[0399] In the first embodiment, the communication device is configured to perform the operations of a mobility management network element. The processing unit 1710 is configured to determine the sleep time information of the terminal device based on the satellite coverage information of the terminal device. The satellite coverage information indicates the time period during which the terminal device is covered by the satellite network and / or the time period during which the terminal device is not covered by the satellite network. The sleep time period corresponding to the sleep time information includes the time period during which the terminal device is not covered by the satellite network. The transceiver unit 1720 is configured to transmit the sleep time information to the terminal device.

[0400] In a possible implementation, the processing unit 1710 is configured to determine one or more of the eDRX cycle, periodic TAU cycle, or periodic registration cycle of the terminal device based on the satellite coverage information. The sleep time information includes a sleep start time, and the sleep start time is within the eDRX cycle, periodic TAU cycle, or periodic registration cycle.

[0401] In a possible implementation, the sleep time information includes a sleep start time and a sleep end time, or the sleep time information includes a sleep start time and a sleep period.

[0402] In a possible implementation, the processing unit 1710 is configured to receive the satellite coverage information using the transceiver unit 1720. Alternatively, the transceiver unit 1720 receives the ephemeris information of the satellite cell where the terminal device is located and determines the satellite coverage information based on the ephemeris information.

[0403] In a possible implementation method, the processing unit 1710 is configured to determine that the position of the terminal device is fixed or the movement trajectory of the terminal device is fixed.

[0404] In a possible implementation method, when the deregistration timer corresponding to the terminal device expires, the processing unit 1710 is configured to determine, based on the satellite coverage information, that the terminal device is not covered by the satellite network, and also determine to skip performing deregistration on the terminal device.

[0405] In the second embodiment, the communication device is configured to perform the operation of the mobility management network element. When the deregistration timer corresponding to the terminal device expires, the processing unit 1710 is configured to determine, based on the satellite coverage information of the terminal device, that the terminal device is not covered by the satellite network. The satellite coverage information indicates the time period during which the terminal device is covered by the satellite network and / or the time period during which the terminal device is not covered by the satellite network. The processing unit 1710 is also configured to determine to skip performing deregistration or detachment on the terminal device in response to the case where the terminal device is not covered by the satellite network.

[0406] In a possible implementation method, the transceiver unit 1720 is configured to transmit first information to the terminal device. The first information indicates that when the terminal device has uplink transmission requirements, the terminal device performs uplink transmission based on the satellite network coverage status.

[0407] In a possible implementation method, the first information is satellite coverage information, and the first information clearly indicates that when the terminal device has uplink transmission requirements, the terminal device starts uplink transmission based on the satellite coverage information.

[0408] In a possible implementation method, the transceiver unit 1720 is configured to transmit satellite coverage information to a terminal device, and the first information clearly indicates that when the terminal device has an uplink transmission requirement, the terminal device starts uplink transmission based on the satellite coverage information.

[0409] In a possible implementation method, the uplink transmission requirement includes one or more of a periodic TAU, a periodic registration, or an uplink data transmission.

[0410] In a possible implementation manner, the processing unit 1710 is configured to receive satellite coverage information using the transceiver unit 1720. Alternatively, the transceiver unit 1720 receives ephemeris information of a satellite cell in which the terminal device is located, and determines the satellite coverage information based on the ephemeris information.

[0411] In a possible implementation method, the processing unit 1710 is configured to determine that the position of the terminal device is fixed or to determine that the movement trajectory of the terminal device is fixed.

[0412] In a third embodiment, the communication device is configured to perform an operation of a mobility management network element. The processing unit 1710 is configured to determine satellite coverage information of a terminal device, the satellite coverage information indicating a time period when the terminal device is covered by a satellite network and / or indicating a time period when the terminal device is not covered by the satellite network, and the processing unit 1710 is also configured to determine a maximum waiting time based on the satellite coverage information, the maximum waiting time indicating a maximum period when the terminal device waits until it is reachable.

[0413] In a possible implementation method, the processing unit 1710 is configured to determine that the terminal device is unreachable based on satellite coverage information.

[0414] In a possible implementation method, the processing unit 1710 is configured to receive satellite coverage information using the transceiver unit 1720.

[0415] In a possible implementation method, the processing unit 1710 is configured to receive the ephemeris information of the satellite cell where the terminal device is located using the transceiver unit 1720, and to determine the satellite coverage information based on the ephemeris information.

[0416] In a possible implementation method, the processing unit 1710 is configured to transmit a paging message to an access network device using the transceiver unit 1720, the paging message includes the identification information of the terminal device, and the paging message indicates that the terminal device is to be paged. The processing unit 1710 is also configured to receive a first message from the access network device using the transceiver unit 1720. The first message includes a paging failure indication and the satellite coverage information of the terminal device. The paging failure indication indicates that the reason for the paging failure is that the terminal device is not covered by the satellite network. Optionally, the paging failure indication further indicates that the mobility management network element needs to perform reachability determination / paging based on the satellite coverage information.

[0417] In a possible implementation method, the processing unit 1710 is configured to determine that the position of the terminal device is fixed, or to determine that the movement trajectory of the terminal device is fixed.

[0418] In the fourth embodiment, the communication device is configured to perform the operations of the terminal device. The transceiver unit 1720 is configured to receive first information, where the first information indicates that the terminal device performs uplink transmission based on the satellite network coverage status when the terminal device has uplink transmission requirements. The processing unit 1710 is configured to determine, based on the first information, that the terminal device is not covered by the satellite network when the terminal device has uplink transmission requirements, and also to determine to skip performing uplink transmission.

[0419] In a possible implementation, the first information is satellite coverage information. The satellite coverage information indicates the time period during which the terminal device is covered by the satellite network and / or the time period during which the terminal device is not covered by the satellite network. The first information clearly indicates that the terminal device starts uplink transmission based on the satellite coverage information when the terminal device has uplink transmission requirements.

[0420] In a possible implementation, the processing unit 1710 is configured to receive satellite coverage information using the transceiver unit 1720. The satellite coverage information indicates the time period during which the terminal device is covered by the satellite network and / or the time period during which the terminal device is not covered by the satellite network. The first information clearly indicates that the terminal device starts uplink transmission based on the satellite coverage information when the terminal device has uplink transmission requirements.

[0421] In a possible implementation, the uplink transmission requirements include one or more of periodic TAU, periodic registration, or uplink data transmission.

[0422] In the fifth embodiment, the communication device is configured to perform the operations of the terminal device. The transceiver unit 1720 is configured to receive sleep time information, and the sleep time period corresponding to the sleep time information includes a time period during which the terminal device is not covered by the satellite network. The sleep time information is determined based on the satellite coverage information of the terminal device, and the satellite coverage information indicates a time period during which the terminal device is covered by the satellite network and / or a time period during which the terminal device is not covered by the satellite network. The processing unit 1710 is configured to perform sleep based on the sleep time information.

[0423] In a possible implementation method, the sleep time information includes a sleep start time, and the sleep start time is within the eDRX cycle of the terminal device, the periodic TAU cycle of the terminal device, or the periodic registration cycle of the terminal device.

[0424] In a possible implementation method, the sleep time information includes a sleep start time and a sleep end time, or the sleep time information includes a sleep start time and a sleep period.

[0425] In the sixth embodiment, the communication device is configured to perform the operations of the access network device. The processing unit 1710 is configured to obtain satellite coverage information or ephemeris information of the satellite cell, and the satellite coverage information indicates a time period during which the satellite cell is covered by the satellite network and / or a time period during which the satellite cell is not covered by the satellite network. The transceiver unit 1720 is configured to transmit the satellite coverage information or ephemeris information of the satellite cell to the mobility management network element.

[0426] In a possible implementation method, in the N2 interface setup procedure, the transceiver unit 1720 is configured to send satellite coverage information or ephemeris information corresponding to the satellite cell of the access network device to the mobility management network element.

[0427] In a possible implementation method, in the registration procedure of the terminal device, the transceiver unit 1720 is configured to send satellite coverage information or ephemeris information of the satellite cell where the terminal device is located to the mobility management network element.

[0428] In a possible implementation method, the transceiver unit 1720 is configured to receive a paging message from the mobility management network element. The paging message includes the identification information of the terminal device and indicates that the terminal device is being paged. The processing unit 1710 is configured to determine that the terminal device is unreachable based on the satellite coverage information of the satellite cell where the terminal device is located, and to send a first message to the mobility management network element using the transceiver unit 1720. The first message includes a paging failure indication and the satellite coverage information of the terminal device. The paging failure indication indicates that the reason for this paging failure is that the terminal device is not covered by the satellite network. Optionally, the paging failure indication further indicates that the mobility management network element needs to perform reachability determination / paging based on the satellite coverage information.

[0429] In the seventh embodiment, the communication device is configured to perform the operations of the mobility management network element. The processing unit 1710 is configured to determine the periodic TAU cycle of the terminal device based on the satellite coverage information of the terminal device, and the transceiver unit 1720 is configured to transmit the periodic TAU cycle to the terminal device. Alternatively, the processing unit 1710 is configured to determine the periodic registration cycle of the terminal device based on the satellite coverage information of the terminal device, and the transceiver unit 1720 is configured to transmit the periodic registration cycle to the terminal device, where the satellite coverage information indicates the time period during which the terminal device is covered by the satellite network and / or the time period during which the terminal device is not covered by the satellite network.

[0430] In a possible implementation, the time period corresponding to the periodic TAU cycle includes the time period during which the terminal device is not covered by the satellite network, or the time period corresponding to the periodic registration cycle includes the time period during which the terminal device is not covered by the satellite network.

[0431] In a possible implementation, the processing unit 1710 is further configured to use the transceiver unit 1720 to transmit indication information to the access network device based on the satellite coverage information, where the indication information indicates to the access network device to execute a procedure for releasing the terminal device.

[0432] In a possible implementation, the processing unit 1710 is configured to determine a first period based on the satellite coverage information of the terminal device, where the first period is the period from when the terminal device enters the idle state to before the terminal device enters the sleep state. The transceiver unit 1720 is configured to transmit the first period to the terminal device.

[0433] In a possible implementation method, the transceiver unit 1720 is further configured to send a cause value to the terminal device, and the cause value is discontinuous satellite coverage.

[0434] In a possible implementation method, the cause value further indicates that the terminal device skips performing uplink transmission while in sleep.

[0435] In a possible implementation method, the transceiver unit 1720 is configured to send a GUTI reallocation command to the terminal device, the GUTI reallocation command includes a periodic TAU cycle, or the transceiver unit 1720 is configured to send a TAU acceptance message to the terminal device, and the TAU acceptance message includes a periodic TAU cycle.

[0436] In a possible implementation method, the transceiver unit 1720 is configured to send a setting update command to the terminal device, the setting update command includes a periodic registration cycle, or the transceiver unit 1720 is configured to send a mobility registration update acceptance message to the terminal device, and the mobility registration update acceptance message includes a periodic registration cycle.

[0437] In the eighth embodiment, the communication device is configured to perform the operation of the terminal device. The transceiver unit 1720 is configured to receive a periodic TAU cycle from the mobility management network element, and the processing unit 1710 is configured to perform a periodic TAU based on the periodic TAU cycle. The time period corresponding to the periodic TAU cycle includes a time period during which the terminal device is not covered by the satellite network. Alternatively, the transceiver unit 1720 is configured to receive a periodic registration cycle from the mobility management network element, and the processing unit 1710 is configured to perform a periodic registration based on the periodic registration cycle. The time period corresponding to the periodic registration cycle includes a time period during which the terminal device is not covered by the satellite network.

[0438] In a possible implementation method, the periodic TAU cycle or the periodic registration cycle is determined based on the satellite coverage information of the terminal device, and the satellite coverage information indicates the time period during which the terminal device is covered by the satellite network and / or the time period during which the terminal device is not covered by the satellite network.

[0439] In a possible implementation method, the processing unit 1710 is configured to use the transceiver unit 1720 to send a TAU request to the mobility management network element based on the satellite coverage information of the terminal device before the transceiver unit 1720 receives a periodic TAU cycle from the mobility management network element, or to use the transceiver unit 1720 to send a mobility registration update request to the mobility management network element based on the satellite coverage information of the terminal device before the transceiver unit 1720 receives a periodic registration cycle from the mobility management network element, and the satellite coverage information indicates the time period during which the terminal device is covered by the satellite network and / or the time period during which the terminal device is not covered by the satellite network.

[0440] In a possible implementation method, the transceiver unit 1720 is further configured to receive a first period from the mobility management network element, where the first period is the period from after the terminal device enters the idle state to before the terminal device enters the sleep state, and the first period is determined based on the satellite coverage information of the terminal device.

[0441] In a possible implementation method, the transceiver unit 1720 is configured to receive a cause value from the mobility management network element, and the cause value is discontinuous satellite coverage.

[0442] In a possible implementation method, the cause value further indicates skipping the uplink transmission when the terminal device is in sleep. When there is an uplink transmission requirement, based on the cause value, it is determined to skip the uplink transmission.

[0443] In the ninth embodiment, the communication device is configured to perform the operations of the access network device. The processing unit 1710 is configured to use the transceiver unit 1720 to send a context release request to the mobility management network element based on the satellite coverage information of the terminal device. The context release request is used to request the mobility management network element to release the context of the terminal device. The satellite coverage information indicates the time period during which the terminal device is covered by the satellite network and / or the time period during which the terminal device is not covered by the satellite network. The transceiver unit 1720 is further configured to receive a periodic TAU cycle from the mobility management network element and send the periodic TAU cycle to the terminal device. The time period corresponding to the periodic TAU cycle includes the time period during which the terminal device is not covered by the satellite network. Alternatively, the transceiver unit 1720 is further configured to receive a periodic registration cycle from the mobility management network element and send the periodic registration cycle to the terminal device. The time period corresponding to the periodic registration cycle includes the time period during which the terminal device is not covered by the satellite network.

[0444] For a more detailed description of the processing unit 1710 and the transceiver unit 1720, please directly refer to the relevant description in the method embodiment. Details are not described again in this specification.

[0445] As shown in FIG. 18, communication device 1800 includes processor 1810. Optionally, communication device 1800 may further include interface circuit 1820. Processor 1810 and interface circuit 1820 are coupled to each other. Interface circuit 1820 may be understood to be a transceiver or an input / output interface. Optionally, communication device 1800 may further include memory 1830 configured to store instructions executed by processor 1810, or input data required by processor 1810 to operate the instructions, or data generated after processor 1810 operates the instructions.

[0446] When communication device 1800 is configured to implement the foregoing method embodiments, processor 1810 is configured to implement the functions of processing unit 1710, and interface circuit 1820 is configured to implement the functions of transceiver unit 1720.

[0447] The processor in the embodiments of the present application may be a central processing unit (CPU), or may be any other general-purpose processor, digital signal processor (DSP), application-specific integrated circuit (ASIC), field programmable gate array (FPGA), or other programmable logic device, transistor logic device, hardware component, or any combination thereof. The general-purpose processor may be a microprocessor or any ordinary processor.

[0448] The method steps in the embodiments of this application can be implemented in a hardware manner or in a manner of executing software instructions by a processor. The software instructions may include corresponding software modules. The software modules may be stored in a random access memory, a flash memory, a read-only memory, a programmable read-only memory, an erasable programmable read-only memory, an electrically erasable programmable read-only memory, a register, a hard disk, a removable hard disk, a CD-ROM, or any other form of storage medium well known in the art. For example, the storage medium is coupled to the processor so that the processor can read information from the storage medium or write information to the storage medium. Certainly, the storage medium may be a component of the processor. The processor and the storage medium may be disposed within an ASIC. In addition, the ASIC may be located in a base station or a terminal. Certainly, the processor and the storage medium may exist in the base station or the terminal as discrete components.

[0449] All or part of the foregoing embodiments may be implemented using software, hardware, firmware, or any combination thereof. When software is used to implement an embodiment, all or part of the embodiment may be implemented in the form of a computer program product. A computer program product includes one or more computer programs or instructions. When the computer program or instructions are loaded and executed on a computer, the procedures or functions according to the embodiments of the present application are implemented in whole or in part. The computer may be a general-purpose computer, a dedicated computer, a computer network, a base station, a user device, or another programmable device. The computer program or instructions may 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 program or instructions may be transmitted in a wired or wireless manner from a website, a computer, a server, or a data center to another website, a computer, a server, or a data center. The computer-readable storage medium may be any usable medium accessible by a computer, or a data storage device such as a server or a data center that integrates one or more usable media. The usable medium may be a magnetic medium (such as a floppy disk, a hard disk, or a magnetic tape), or an optical medium (such as a digital video disk), or a semiconductor medium (such as a solid state disk). The computer-readable storage medium may be a volatile storage medium or a non-volatile storage medium, or may include two types of storage media, namely a volatile storage medium and a non-volatile storage medium.

[0450] In the embodiments of the present application, unless otherwise specified or there is no logical contradiction, the terms and / or descriptions in different embodiments are consistent and may be referenced to each other. The technical features in different embodiments may be combined based on their internal logical relationships to form new embodiments.

[0451] In this application, "at least one" means one or more, and "a plurality of" means two or more. The term "and / or" describes the relationship between related objects and can indicate three relationships. For example, A and / or B can indicate the following cases: only A exists, both A and B exist, and only B exists. Here, A and B can be singular or plural. In the text description of this application, the character " / " generally indicates an "or" relationship between related objects. In the mathematical formulas of this application, the character " / " indicates a "division" relationship between related objects.

[0452] The various numbers in the embodiments of this application are used merely for the purpose of easy distinction in the description and may be understood not to be used for limiting the scope of the embodiments of this application. The sequential numbers of the foregoing processes do not mean the execution order, and the execution order of the processes is determined based on the functions and internal logics of the processes.

Claims

1. A communication method, comprising: determining a periodic registration cycle of the terminal device based on satellite coverage information of the terminal device; transmitting the periodic registration cycle to the terminal device; determining a first period based on the satellite coverage information of the terminal device, wherein the first period is a period from when the terminal device enters an idle state to before the terminal device enters a sleep state; transmitting the first period to the terminal device; wherein the satellite coverage information indicates at least one of a time period during which the terminal device is covered by a satellite network and a time period during which the terminal device is not covered by the satellite network.

2. The time period corresponding to the periodic registration cycle includes the time period during which the terminal device is not covered by the satellite network. The method according to claim 1.

3. The method further includes: transmitting indication information to an access network device based on the satellite coverage information, wherein the indication information indicates to the access network device to execute a procedure for releasing the terminal device. The method according to claim 1 or 2.

4. The method further includes: transmitting a cause value to the terminal device, wherein the cause value indicates skipping uplink transmission when the terminal device is in sleep. The method according to claim 1 or 2.

5. A communication method, comprising: receiving a periodic registration cycle from a mobility management network element; performing periodic registration based on the periodic registration cycle, wherein the time period corresponding to the periodic registration cycle includes a time period during which the terminal device is not covered by a satellite network; receiving a first period from the mobility management network element, wherein the first period is a period from when the terminal device enters an idle state to before the terminal device enters a sleep state, and the first period is determined based on satellite coverage information of the terminal device; wherein

6. The periodic registration cycle is determined based on satellite coverage information of the terminal device, and the satellite coverage information indicates at least one of a time period during which the terminal device is covered by the satellite network and a time period during which the terminal device is not covered by the satellite network. The method according to claim 5.

7. Before the step of receiving the periodic registration cycle from the mobility management network element, the method further comprises: sending a mobility registration update request to the mobility management network element based on satellite coverage information of the terminal device, wherein the satellite coverage information indicates at least one of a time period during which the terminal device is covered by the satellite network and a time period during which the terminal device is not covered by the satellite network. The method according to claim 5 or 6.

8. The method further comprises: receiving a cause value from the mobility management network element, wherein the cause value is discontinuous satellite coverage. The method according to claim 5 or 6.

9. The cause value further indicates skipping the performance of uplink transmission while the terminal device is in sleep, and the method further comprises: when there is an uplink transmission requirement, determining to skip performing uplink transmission based on the cause value. The method according to claim 8.

10. A communication device comprising a processor and an interface circuit, wherein the interface circuit is configured to receive a signal from a communication device other than the communication device and transmit the signal to the processor, or transmit a signal from the processor to a communication device other than the communication device, and the processor is configured to implement the method according to claim 1 or 2 by using logic circuits or by executing code instructions.

11. A computer-readable storage medium storing a computer program or instructions, wherein when the computer program or the instructions are executed by a communication device, the method according to claim 1 or 2 is implemented.

12. A computer program which, when executed by a communication device, implements the method according to claim 1 or 2. **Claim 13** A communication device comprising a processor and an interface circuit, wherein the interface circuit is configured to receive a signal from a communication device other than the communication device and transmit the signal to the processor, or to transmit a signal from the processor to a communication device other than the communication device, and the processor is configured to implement the method according to claim 5 or 6 by using a logic circuit or by executing code instructions. **Claim 14** A computer-readable storage medium storing a computer program or instructions, wherein the method according to claim 5 or 6 is implemented when the computer program or the instructions are executed by a communication device. **Claim 15** A computer program which, when executed by a communication device, implements the method according to claim 5 or 6.

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