Network selection method and device

Abstract

The present application provides a method for selecting a network. The method may include: the mobility management network element of the first upper network obtains second indication information, the second indication information indicates whether the first lower network can provide Internet Protocol Multimedia Network Subsystem IMS voice service through a packet switching PS session accessed by a new radio interface NR cell; determines first indication information based on the second indication information, the first indication information indicates whether the first upper network can support the provision of IMS voice service through a PS session accessed by a non-third generation partnership project N3GPP; sends the first indication information to a terminal device. The solution of the present application can enable the terminal device to select a lower network access that can provide IMS voice service according to the indication information, thereby ensuring the service quality of the terminal device using the IMS voice service in the upper network.

Description

Technical Field

[0001] The present application relates to the field of communications, and more particularly, to a method and apparatus for network selection. Background Art

[0002] A non-public network (NPN) is a non-public 5G network that can be implemented by relying on the network functions of a public land mobile network (PLMN), such as a public network integrated NPN (PNI-NPN), or it can be implemented without relying on the network functions of a PLMN, such as a standalone NPN (SNPN).

[0003] Third Generation Partnership Project (3 rd generation partnership project (3GPP) in R16 using non-3GPP interworking features (non-3 rd The 3GPP (network generation partnership project interworking function, N3IWF) architecture supports the interworking between SNPN and PLMN, that is, the user equipment (UE) is dual-signed to SNPN and PLMN respectively. For example, the UE performs 3GPP registration in the lower network (the lower network can be SNPN) (accessed through the access network of the lower network), establishes a protocol data unit (PDU) session in the SNPN, and then selects the N3IWF of the upper network and establishes an Internet protocol security (IPSec) connection to the N3IWF of the upper network (the upper network can be PLMN) through the PDU session in the SNPN, and sends a registration request to the upper network through the IPSec connection, thereby registering in the upper network PLMN through the lower network.

[0004] After the UE accesses the upper network from the lower network, when the UE initiates an Internet Protocol Multimedia Core Network Subsystem IMS (IMS) voice service through the upper network, the service quality of the voice service is sometimes not guaranteed. Summary of the invention

[0005] The present application provides a network selection method and apparatus, so that a terminal device selects a lower layer network or upper layer network access that can provide an IMS voice service according to indication information, thereby ensuring the service quality of the terminal device using the Internet Protocol Multimedia Network Subsystem IMS voice service.

[0006] In a first aspect, a method for network selection is provided. The method can be executed by a mobility management network element of a first upper network. The method includes: obtaining second indication information, the second indication information indicating whether the first lower network can provide Internet Protocol Multimedia Network Subsystem IMS voice service through a packet switched (PS) session accessed by a new radio (NR) cell; determining first indication information based on the second indication information, the first indication information indicating whether the first upper network can support the provision of IMS voice service through a PS session accessed by a non-third generation partnership project N3GPP; and sending the first indication information to a terminal device.

[0007] Based on the above scheme, the mobility management network element of the first upper layer network can learn that the terminal device accesses the first upper layer network through the first lower layer network, and whether the first lower layer network can support IMS voice services, and further determine whether the first upper layer network can provide IMS voice service support for the terminal device, and notify the terminal device of this information, so that the terminal device selects a network that can support the provision of IMS voice services to initiate IMS voice services, so as to obtain normal and guaranteed voice call quality.

[0008] Optionally, the mobility management network element of the first upper layer network receives a registration request message from the terminal device or an N2 message from an N3GPP interworking function network element, and the registration request message or the N2 message includes the second indication information.

[0009] Optionally, the mobility management network element of the first upper layer network obtains the second indication information according to local configuration.

[0010] Optionally, the local configuration also includes an identifier of the first lower network.

[0011] Optionally, the mobility management network element of the first upper layer network receives a registration request message from the terminal device or an N2 message from the N3GPP interworking function network element, and the registration request message or the N2 message includes third indication information, and the third indication information indicates whether the terminal device accesses the first upper layer network through the protocol data unit PDU session of the first lower layer network, or the third indication information indicates the network identifier of the first lower layer network.

[0012] Based on the above scheme, the mobility management network element of the first upper layer network can determine the second indication information according to the locally configured service-level agreement (SLA) and the third indication information. The scheme has a simple process, saves signaling overhead, and is easier to implement.

[0013] Optionally, the SLA is configured in the N3GPP interworking function network element, and the N3GPP interworking function network element receives an IPSec message from the terminal device, the IPSec message includes a registration request message, and the IPSec message also includes third indication information, the third indication information indicates whether the terminal device accesses the first upper network through the protocol data unit PDU session of the first lower network, or the third indication information indicates the network identifier of the first lower network, or the N3GPP interworking function network element is a dedicated N3GPP interworking function network element, and the third indication information is determined according to the local configuration. According to the third indication information and the SLA, the second indication information is determined, and then the second indication information is sent to the mobility management network element of the first upper network through the N2 message.

[0014] In a second aspect, a method for network selection is provided. The method may be performed by a mobility management network element of a first lower network. The method includes: determining second indication information, the second indication information indicating whether the first lower network can provide an Internet Protocol Multimedia Network Subsystem IMS voice service through a packet switching PS session accessed by a new radio interface NR cell; and sending the second indication information to a terminal device.

[0015] Based on the above scheme, the mobility management network element of the first lower network informs the mobility management network element of the first upper network through the second indication information whether the first lower network can support IMS voice services, so that the mobility management network element of the first upper network can further determine whether the first upper network can provide support for IMS voice services for terminal devices accessing the first upper network through the first lower network, and notify the terminal device of this information. The terminal device selects a network that can support the provision of IMS voice services to initiate IMS voice services, so as to obtain normal and guaranteed voice call quality.

[0016] Optionally, the second indication information is determined based on local configuration and capabilities of the terminal device.

[0017] Optionally, the second indication information can also be determined based on the data network name DNN of the terminal device session and the single network slice selection auxiliary information S-NSSAI.

[0018] Optionally, a second message is sent to the access network device of the first lower network, where the second message is used to query whether the first lower network can provide IMS voice services through a PS session accessed by the NR cell; and second indication information is received from the access network device.

[0019] Optionally, the second message also includes the capabilities of the terminal device.

[0020] Optionally, if the second message does not carry the capabilities of the terminal device, a first message from the access network device of the first lower network is received, and the first message includes the capabilities of the terminal device.

[0021] Optionally, the second indication information from the access network device may be carried in the first message.

[0022] In a third aspect, a method for network selection is provided. The method can be executed by a terminal device, or it can also be executed by a chip or circuit configured in the terminal device, and the present application does not limit this. The method includes: receiving a second indication information from a mobility management network element of a first lower network, the second indication information indicating that the first lower network can provide Internet Protocol Multimedia Network Subsystem IMS voice services through a packet switching PS session accessed by a new air interface NR cell; selecting a non-third generation partnership project access N3GPP interworking function network element of the first upper network according to the second indication information and accessing the first upper network through the first lower network and the N3GPP interworking function network element; receiving a first indication information from a mobility management network element of the first upper network, the first indication information indicating whether the first upper network can support the provision of IMS voice services through a PS session of N3GPP.

[0023] Based on the above scheme, after the terminal device receives the first indication information and the second indication information, it selects an upper-layer network access that can support the IMS voice service according to the first indication information; if the first upper-layer network does not support the IMS voice service, it selects other upper-layer network access that can support the IMS voice service. In this way, after the terminal device accesses the first lower-layer network that can provide the IMS voice service, the service quality of the terminal device using the IMS voice service in the upper-layer network is guaranteed.

[0024] Optionally, fourth indication information is received from a mobility management network element of a second lower layer network, and the fourth indication information indicates that the second lower layer network cannot provide IMS voice services through a PS session accessed through an NR cell; and the terminal device selects the first lower layer network.

[0025] Based on the above scheme, we can know that before the terminal device selects the first lower network for access, it first selects the second lower network, and learns from the second lower network that the second lower network cannot provide IMS voice services through the PS session accessed by the NR cell, so it chooses to access the first lower network.

[0026] Optionally, second indication information is sent to the mobility management network element of the first upper layer network, and the second indication information is used by the mobility management network element of the first upper layer network to determine the first indication information.

[0027] Optionally, when the second indication information indicates that the first lower network can provide IMS voice services through the PS session accessed by the NR cell, the terminal device will send the second indication information to the mobility management network element of the first upper network. The mobility management network element of the first upper network determines the first indication information. If the first lower network cannot provide IMS voice services through the PS session accessed by the NR cell, the terminal device selects a lower network that can provide IMS voice services through the PS session accessed by the NR cell.

[0028] Optionally, when the first indication information indicates that the first upper layer network cannot support the provision of IMS voice services through PS sessions accessed through N3GPP, the terminal device selects the N3GPP interworking function network element of the second upper layer network, and accesses the second upper layer network through the first lower layer network and the N3GPP interworking function network element; or, the terminal device accesses a third network through a 3GPP access type, and the third network includes the first upper layer network.

[0029] It should be understood that the first indication information indicates that the first upper network cannot support the provision of IMS voice services through the PS session accessed by N3GPP, which is divided into two cases: in the first case, the first lower network supports IMS voice services, but the first upper network does not support IMS voice services; in the second case, the first lower network does not support IMS voice services, but the first upper network supports IMS voice services. If it is the first case, the terminal device needs to select the N3GPP intercommunication function network element of the third upper network, access the third upper network through the first lower network and the N3GPP intercommunication function network element of the third upper network, or directly access the third network through the 3GPP access type (through the access network device). If it is the second case, the terminal device needs to select a second lower network that can provide IMS voice services through a PS session accessed by the NR cell, or directly access the third network through the 3GPP access type (through the access network device).

[0030] Optionally, a registration request message is sent to the mobility management network element of the first upper layer network or an Internet security protocol message is sent to the N3GPP interworking function network element of the first upper layer network, and the registration request message or the Internet security protocol message includes the second indication information.

[0031] Optionally, when the terminal device sends a registration request message to the mobility management network element of the first upper network or sends an Internet security protocol message to the N3GPP interworking function network element of the first upper network, it means that the first lower network can provide IMS voice services through the PS session accessed by the NR cell. In other words, the registration request message or the Internet security protocol message can implicitly indicate that the first lower network can provide IMS voice services through the PS session accessed by the NR cell. This solution saves signaling overhead compared to the explicit indication solution in which the registration request message or the Internet security protocol message carries the second indication information.

[0032] Optionally, a registration request message is sent to the mobility management network element of the first upper layer network or an Internet security protocol message is sent to the N3GPP interworking function network element of the first upper layer network, the registration request message or the Internet security protocol message includes third indication information, the third indication information indicates whether the terminal device accesses the first upper layer network through the protocol data unit PDU session of the first lower layer network, or the third indication information indicates the network identifier of the first lower layer network.

[0033] Optionally, after the terminal device receives the first indication information, the terminal device saves the first indication information; and selects the N3GPP intercommunication function network element of the first upper layer network according to the first indication information.

[0034] Further, if the terminal device determines, based on the first indication information, that the first upper layer network cannot support provision of IMS voice services through a PS session accessed via N3GPP, the terminal device does not select the N3GPP interworking function network element of the first upper layer network.

[0035] Optionally, receiving capability request information from an access network device of a first lower network, the capability request information being used to request the capability of the terminal device; and sending a third message to the access network device of the lower network, the third message including the capability of the terminal device.

[0036] In a fourth aspect, a method for network selection is provided. The method can be executed by an access network device of a first lower network, or it can also be executed by a chip or circuit configured in the access network device, and the present application does not limit this. The method includes: determining second indication information based on local configuration and the capabilities of the terminal device, the second indication information indicating whether the first lower network can provide Internet Protocol Multimedia Network Subsystem IMS voice services through a packet switching PS session accessed by a new air interface NR cell; the access network device of the first lower network sends the second indication information to the mobility management network element of the first lower network.

[0037] Based on the above scheme, the access network device sends the second indication information of whether the first lower layer network can support the IMS voice service to the mobility management network element of the first lower layer network, so that the mobility management network element of the first lower layer network can determine whether the first lower layer network can support the IMS voice service, and notify the terminal device whether the first lower layer network can support the IMS voice service, so that the terminal device can select the network access that can support the IMS voice service, thereby ensuring the service quality of the terminal device using the IMS voice service.

[0038] Optionally, the access network device of the first lower layer network receives a second message from the mobility management network element of the first lower layer network, and the second message is used to query whether the first lower layer network can provide IMS voice services through a PS session accessed by the NR cell.

[0039] Optionally, the second message also includes capabilities of the terminal device.

[0040] Optionally, if the second message does not carry the capabilities of the terminal device, the access network device of the lower network sends a first message to the mobility management network element of the first lower network, and the first message includes the capabilities of the terminal device.

[0041] Optionally, if the second message does not carry the capabilities of the terminal device, the access network device of the lower network sends capability request information to the terminal device, and the capability request information is used to request the capabilities of the terminal device; the access network device of the lower network receives a third message from the terminal device, and the third message includes the capabilities of the terminal device.

[0042] In a fifth aspect, a network selection device is provided, which may be a mobility management network element of a first upper network. The device includes a processing unit and a transceiver unit: the processing unit is used to obtain second indication information, the second indication information indicating whether the first lower network can provide Internet Protocol Multimedia Network Subsystem IMS voice service through a packet switching PS session accessed by a new radio interface NR cell; the processing unit is also used to determine first indication information based on the second indication information, the first indication information indicating whether the first upper network can support the provision of IMS voice service through a PS session accessed by a non-third generation partnership project N3GPP; the transceiver unit sends the first indication information to a terminal device.

[0043] Based on the above scheme, the device can know that the terminal device accesses the first upper network through the first lower network, and whether the first lower network can support IMS voice services, and further determine whether the first upper network can provide IMS voice service support for the terminal device, and notify the terminal device of this information, so that the terminal device selects a network that can support the provision of IMS voice services to initiate IMS voice services, so as to obtain normal and guaranteed voice call quality.

[0044] Optionally, the transceiver unit is further used to receive a registration request message from the terminal device or an N2 message from an N3GPP interworking function network element, and the registration request message or the N2 message includes the second indication information.

[0045] Optionally, the processing unit is specifically used to obtain the second indication information according to local configuration.

[0046] Optionally, the local configuration also includes an identifier of the first lower network.

[0047] Optionally, the transceiver unit is also used to receive a registration request message from the terminal device or an N2 message from an N3GPP interworking function network element, the registration request message or the N2 message includes third indication information, the third indication information indicates whether the terminal device accesses the first upper layer network through the protocol data unit PDU session of the first lower layer network, or the third indication information indicates the network identifier of the first lower layer network.

[0048] Based on the above solution, the mobility management network element of the upper network can determine the second indication information according to the locally configured service level agreement SLA and the third indication information. The solution has a simple process, saves signaling overhead, and is easier to implement.

[0049] Optionally, the SLA is configured in the N3GPP interworking function network element, and the N3GPP interworking function network element receives an IPSec message from the terminal device, the IPSec message includes a registration request message, and the IPSec message also includes third indication information, the third indication information indicates whether the terminal device accesses the first upper network through the protocol data unit PDU session of the first lower network, or the third indication information indicates the network identifier of the first lower network, or the N3GPP interworking function network element is a dedicated N3GPP interworking function network element, and the third indication information is determined according to the local configuration. The second indication information is determined according to the third indication information and the service level agreement SLA, and then the second indication information is sent to the mobility management network element of the first upper network through the N2 message.

[0050] In a sixth aspect, a network selection device is provided, which may be a mobility management network element of a first lower network. The device includes a processing unit and a transceiver unit: the processing unit is used to determine second indication information, the second indication information indicating whether the first lower network can provide an Internet Protocol Multimedia Network Subsystem IMS voice service through a packet switching PS session accessed by a new radio interface NR cell; the transceiver unit is used to send the second indication information to a terminal device.

[0051] Based on the above scheme, the device informs the mobility management network element of the first upper network through the second indication information whether the first lower network can support the IMS voice service, so that the mobility management network element of the first upper network can further determine whether the first upper network can provide support for the IMS voice service for the terminal device accessing the first upper network through the first lower network, and notify the terminal device of this information. The terminal device selects a network that can support the provision of IMS voice services to initiate the IMS voice service, so as to obtain normal and guaranteed voice call quality.

[0052] Optionally, the processing unit is specifically configured to determine the second indication information according to local configuration and capabilities of the terminal device.

[0053] Optionally, the processing unit can also determine the second indication information based on the data network name DNN of the terminal device session and the single network slice selection auxiliary information S-NSSAI.

[0054] Optionally, the transceiver unit is further used to receive a first message from an access network device of the first lower network, where the first message includes the capability of the terminal device.

[0055] Optionally, the transceiver unit is also used to send a second message to the access network device of the first lower network, where the second message is used to query whether the first lower network can provide IMS voice services through a PS session accessed by the NR cell; the transceiver unit is also used to receive second indication information from the access network device.

[0056] Optionally, the second message also includes capabilities of the terminal device.

[0057] Optionally, the second indication information from the access network device may be carried in the first message.

[0058] In the seventh aspect, a network selection device is provided, which may be a terminal device, or may be a chip or circuit configured in the terminal device, which is not limited in the present application. The device includes a processing unit and a transceiver unit: the transceiver unit is used to receive a second indication information from a mobility management network element of a first lower network, the second indication information indicating that the first lower network can provide an Internet Protocol Multimedia Network Subsystem IMS voice service through a packet switching PS session accessed by a new radio interface NR cell; the processing unit is used to select a non-third generation partnership project access N3GPP interworking function network element of a first upper network according to the second indication information and access the first upper network through the first lower network and the N3GPP interworking function network element; the transceiver unit is also used to receive a first indication information from a mobility management network element of the first upper network, the first indication information indicating whether the first upper network can support the provision of IMS voice services through a PS session of N3GPP.

[0059] Based on the above scheme, after receiving the first indication information and the second indication information, the device selects an upper-layer network access that can support the IMS voice service according to the first indication information; if the first upper-layer network does not support the IMS voice service, other upper-layer network access that can support the IMS voice service is selected, so that after the terminal device accesses the first lower-layer network that can provide the IMS voice service, the service quality of the terminal device using the IMS voice service in the upper-layer network is guaranteed.

[0060] Optionally, the transceiver unit is also used to receive a fourth indication information from a mobility management network element of a second lower layer network, wherein the fourth indication information indicates that the second lower layer network cannot provide IMS voice services through a PS session accessed through an NR cell; the processing unit is also used to select the first lower layer network.

[0061] Optionally, the transceiver unit is further used to send second indication information to the mobility management network element of the first upper network, and the second indication information is used by the mobility management network element of the first upper network to determine the first indication information.

[0062] Optionally, when the second indication information indicates that the first lower network can provide IMS voice services through the PS session accessed by the NR cell, the terminal device will send the second indication information to the mobility management network element of the first upper network. The mobility management network element of the first upper network determines the first indication information. If the first lower network cannot provide IMS voice services through the PS session accessed by the NR cell, the terminal device selects a lower network that can provide IMS voice services through the PS session accessed by the NR cell.

[0063] Optionally, when the first indication information indicates that the first upper layer network cannot support the provision of IMS voice services through PS sessions accessed through N3GPP, the processing unit is used to select an N3GPP interworking function network element of a second upper layer network, and access the second upper layer network through the first lower layer network and the N3GPP interworking function network element; or, the processing unit is used to access a third network through a 3GPP access type, and the third network includes the first upper layer network.

[0064] It should be understood that the first indication information indicates that the first upper network cannot support the provision of IMS voice services through the PS session accessed by N3GPP, which is divided into two cases: in the first case, the first lower network supports IMS voice services, but the first upper network does not support IMS voice services; in the second case, the first lower network does not support IMS voice services, but the first upper network supports IMS voice services. If it is the first case, the processing unit needs to select the N3GPP intercommunication function network element of the third upper network, access the third upper network through the first lower network and the N3GPP intercommunication function network element of the third upper network, or directly access the third network through the 3GPP access type (through the access network device). If it is the second case, the processing unit needs to select a second lower network that can provide IMS voice services through a PS session accessed by the NR cell, or directly access the third network through the 3GPP access type (through the access network device).

[0065] Optionally, the transceiver unit is specifically used to send a registration request message to the mobility management network element of the first upper layer network or to send an Internet security protocol message to the N3GPP intercommunication function network element of the first upper layer network, and the registration request message or the Internet security protocol message includes the second indication information.

[0066] Optionally, when the transceiver unit sends a registration request message to the mobility management network element of the first upper network or sends an Internet security protocol message to the N3GPP interworking function network element of the first upper network, it means that the first lower network can provide IMS voice services through the PS session accessed by the NR cell. In other words, the registration request message or the Internet security protocol message can implicitly indicate that the first lower network can provide IMS voice services through the PS session accessed by the NR cell. This solution saves more signaling overhead than the explicit indication solution in which the registration request message or the Internet security protocol message carries the second indication information.

[0067] Optionally, the transceiver unit is specifically used to send a registration request message to the mobility management network element of the first upper layer network or to send an Internet security protocol message to the N3GPP intercommunication function network element of the first upper layer network, the registration request message or the Internet security protocol message includes third indication information, the third indication information indicates whether the terminal device accesses the first upper layer network through the protocol data unit PDU session of the first lower layer network, or the third indication information indicates the network identifier of the first lower layer network.

[0068] Optionally, the device also includes a storage unit, which is used to store the first indication information; the processing unit is also used to select the N3GPP intercommunication function network element of the first upper layer network according to the first indication information.

[0069] Optionally, the processing unit is used to determine, based on the first indication information, that the first upper layer network cannot support providing IMS voice services through a PS session accessed via N3GPP; the processing unit does not select an N3GPP interworking function network element of the first upper layer network.

[0070] Optionally, the transceiver unit is also used to receive capability request information from an access network device of a lower-layer network, wherein the capability request information is used to request the capability of the terminal device; the transceiver unit is also used to send a third message to the access network device of the lower-layer network, wherein the third message includes the capability of the terminal device.

[0071] In the eighth aspect, a network selection device is provided. The device may be an access network device of the first lower network, or may be a chip or circuit configured in the access network device, which is not limited in the present application. The device includes a processing unit and a transceiver unit: the processing unit is used to determine the second indication information according to the local configuration and the capability of the terminal device, and the second indication information indicates whether the first lower network can provide Internet Protocol Multimedia Network Subsystem IMS voice service through the packet switching PS session accessed by the new air interface NR cell; the transceiver unit is used to send the second indication information to the mobility management network element of the first lower network.

[0072] Based on the above scheme, the device sends the second indication information of whether the first lower layer network can support the IMS voice service to the mobility management network element of the first lower layer network, so that the mobility management network element of the first lower layer network can determine whether the first lower layer network can support the IMS voice service, and notify the terminal device whether the first lower layer network can support the IMS voice service, so that the terminal device can select the network access that can support the IMS voice service, thereby ensuring the service quality of the terminal device using the IMS voice service.

[0073] Optionally, the transceiver unit is also used to receive a second message from the mobility management network element of the first lower network, and the second message is used to query whether the first lower network can provide IMS voice services through a PS session accessed by the NR cell.

[0074] Optionally, the transceiver unit is further used to send a first message to the mobility management network element of the first lower network, where the first message includes the capability of the terminal device.

[0075] Optionally, the transceiver unit is further used to send capability request information to the terminal device, where the capability request information is used to request the capability of the terminal device; the transceiver unit is also used to receive a third message from the terminal device, where the third message includes the capability of the terminal device.

[0076] Optionally, the second message also includes capabilities of the terminal device.

[0077] In a ninth aspect, a communication device is provided, comprising a processor. The processor is coupled to a memory and can be used to execute instructions in the memory to implement the method in any one of the first to fourth aspects and any possible implementation of any one of the first to fourth aspects. Optionally, the communication device also includes a memory. Optionally, the communication device also includes a communication interface, the processor is coupled to the communication interface, and the communication interface is used to input and / or output information. The information includes at least one of an instruction and data.

[0078] In one implementation, the communication device is a mobility management network element, an access network device or a terminal device. When the communication device is a mobility management network element, an access network device or a terminal device, the communication interface may be a transceiver, or an input / output interface.

[0079] In another implementation, the communication device is a chip or a chip system. When the communication device is a chip or a chip system, the communication interface may be an input / output interface, an interface circuit, an output circuit, an input circuit, a pin or a related circuit on the chip or the chip system. The processor may also be embodied as a processing circuit or a logic circuit.

[0080] In another implementation, the communication device is a chip or a chip system configured in a mobility management network element, an access network device or a terminal device.

[0081] Optionally, the transceiver may be a transceiver circuit. Optionally, the input / output interface may be an input / output circuit.

[0082] In a tenth aspect, a processor is provided, comprising: an input circuit, an output circuit, and a processing circuit. The processing circuit is used to receive a signal through the input circuit and transmit a signal through the output circuit, so that the processor executes the method in any possible implementation of the first to fourth aspects and the first to fourth aspects.

[0083] In the specific implementation process, the processor can be one or more chips, the input circuit can be an input pin, the output circuit can be an output pin, and the processing circuit can be a transistor, a gate circuit, a trigger, and various logic circuits. The input signal received by the input circuit can be, for example, but not limited to, received and input by a receiver, and the signal output by the output circuit can be, for example, but not limited to, output to a transmitter and transmitted by the transmitter, and the input circuit and the output circuit can be the same circuit, which is used as an input circuit and an output circuit at different times. The embodiments of the present application do not limit the specific implementation methods of the processor and various circuits.

[0084] In an eleventh aspect, a processing device is provided, comprising a processor and a memory. The processor is used to read instructions stored in the memory, and can receive signals through a receiver and transmit signals through a transmitter to execute the method in any possible implementation of the first to fourth aspects and the first to fourth aspects.

[0085] Optionally, the processor is one or more and the memory is one or more.

[0086] Optionally, the memory may be integrated with the processor, or the memory may be provided separately from the processor.

[0087] In the specific implementation process, the memory can be a non-transitory memory, such as a read-only memory (ROM), which can be integrated with the processor on the same chip or can be set on different chips respectively. The embodiments of the present application do not limit the type of memory and the setting method of the memory and the processor.

[0088] It can be understood that the related data interaction process, such as sending indication information, can be a process of outputting indication information from the processor, and receiving capability information can be a process of receiving input capability information from the processor. Specifically, the data output by the processor can be output to the transmitter, and the input data received by the processor can come from the receiver. Among them, the transmitter and the receiver can be collectively referred to as a transceiver.

[0089] The processing device in the above-mentioned eleventh aspect may be one or more chips. The processor in the processing device may be implemented by hardware or by software. When implemented by hardware, the processor may be a logic circuit, an integrated circuit, etc.; when implemented by software, the processor may be a general-purpose processor implemented by reading software codes stored in a memory, and the memory may be integrated in the processor or located outside the processor and exist independently.

[0090] In the twelfth aspect, a computer program product is provided, which includes: a computer program (also referred to as code, or instruction), which, when executed, enables a computer to execute the method in the above-mentioned first to fourth aspects and any possible implementation of the first to fourth aspects.

[0091] In the thirteenth aspect, a computer-readable storage medium is provided, which stores a computer program (also referred to as code, or instructions). When the computer-readable storage medium is run on a computer, the computer executes the method in the above-mentioned first to fourth aspects and any possible implementation of the first to fourth aspects.

[0092] In a fourteenth aspect, a communication system is provided, comprising the above-mentioned mobility management network element of the first lower network and the access network device of the first lower network. Optionally, the communication system further comprises a mobility management network element of the first upper network or a terminal device. BRIEF DESCRIPTION OF THE DRAWINGS

[0093] Figure 1 It is a schematic diagram of a network architecture provided in an embodiment of the present application.

[0094] Figure 2 It is a schematic diagram of a network scenario architecture applicable to an embodiment of the present application.

[0095] Figure 3 It is a schematic diagram of another network scenario architecture applicable to an embodiment of the present application.

[0096] Figure 4 It is a flowchart of a network selection method 200 provided in an embodiment of the present application.

[0097] Figure 5It is a flowchart of another network selection method 300 provided in an embodiment of the present application.

[0098] Figure 6 It is a flowchart of a method for obtaining whether a lower layer network supports IMS voice service provided in an embodiment of the present application.

[0099] Figure 7 It is a flowchart of another method for obtaining whether a lower layer network supports IMS voice service provided in an embodiment of the present application.

[0100] Figure 8 It is a flowchart of another network selection method 400 provided in an embodiment of the present application.

[0101] Fig. 9 It is a flowchart of another network selection method 500 provided in an embodiment of the present application.

[0102] Fig.10 It is a flowchart of another network selection method 600 provided in an embodiment of the present application.

[0103] Fig.11 It is a flowchart of another network selection method 700 provided in an embodiment of the present application.

[0104] Fig.12 It is a flowchart of another network selection method 800 provided in an embodiment of the present application.

[0105] Fig.13 It is a flowchart of another network selection method 900 provided in an embodiment of the present application.

[0106] Fig.14 It is a schematic block diagram of a communication device provided in an embodiment of the present application.

[0107] Fig.15 It is a schematic block diagram of another communication device provided in an embodiment of the present application.

[0108] Fig.16 It is a schematic diagram of a communication device provided in an embodiment of the present application.

[0109] Fig.17 It is a schematic diagram of another communication device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0110] The technical solution in this application will be described below in conjunction with the accompanying drawings.

[0111] Figure 1 Schematic diagram of a network architecture provided by an embodiment of the present application. Figure 1As shown, the network architecture may include user equipment 110, (wireless) access network equipment 120, user plane network element 130, data network 140, authentication server 150, mobility management network element 160, session management network element 170, application network element 180, unified data management network element 190, policy control network element 191, network function storage library function network element 192, network open network element 193 and network slice selection function network element 194, etc. The following describes each network element involved in the network architecture.

[0112] 1. User equipment (UE) 110: User equipment may also be referred to as a terminal, an access terminal, a user unit, a user station, a mobile station, a mobile station, a remote station, a remote terminal, a mobile device, a user terminal, a wireless communication device, a user agent or a user device. The terminal in the embodiments of the present application can be a mobile phone, a tablet computer, a computer with wireless transceiver function, a virtual reality (VR) terminal, an augmented reality (AR) terminal, a wireless terminal in industrial control, a wireless terminal in self-driving, a wireless terminal in remote medical, a wireless terminal in smart grid, a wireless terminal in transportation safety, a wireless terminal in a smart city, a wireless terminal in a smart home, a cellular phone, a cordless phone, a session initiation protocol (SIP) phone, a wireless local loop (WLL) station, a personal digital assistant (PDA), a handheld device with wireless communication function, a computing device or other processing device connected to a wireless modem, a vehicle-mounted device, a wearable device, a terminal in a 5G network or a terminal in a future evolution network, etc.

[0113] Among them, wearable devices can also be called wearable smart devices, which are a general term for the intelligent design and development of wearable devices for daily wear using wearable technology, such as glasses, gloves, watches, clothing and shoes. Wearable devices are portable devices that are worn directly on the body or integrated into the user's clothes or accessories. Wearable devices are not only hardware devices, but also realize powerful functions through software support, data interaction, and cloud interaction. Broadly speaking, wearable smart devices include full-featured, large-sized, and independent of smartphones to achieve complete or partial functions, such as smart watches or smart glasses, as well as those that only focus on a certain type of application function and need to be used in conjunction with other devices such as smartphones, such as various smart bracelets and smart jewelry for vital sign monitoring.

[0114] 2. (Radio) access network equipment (Radio access network, (R)AN) 120: Access network equipment can also be called access equipment. (R)AN can manage wireless resources, provide access services for user equipment, and complete the forwarding of user equipment data between user equipment and the core network. (R)AN can also be understood as a base station in the network.

[0115] Exemplarily, the access network device in the embodiment of the present application may be any communication device with wireless transceiver function for communicating with user equipment. The access network equipment includes but is not limited to: evolved NodeB (eNB), radio network controller (RNC), Node B (NB), base station controller (BSC), base transceiver station (BTS), home evolved NodeB (HeNB, or home Node B, HNB), baseband unit (BBU), access point (AP) in wireless fidelity (WIFI) system, wireless relay node, wireless backhaul node, transmission point (TP) or transmission and reception point (TRP), etc., and can also be 5G, such as gNB in ​​NR system, or transmission point (TRP or TP), one or a group of (including multiple antenna panels) antenna panels of a base station in 5G system, or, it can also be a network node constituting a gNB or a transmission point, such as a baseband unit (BBU), or a distributed unit (DU), etc.

[0116] In some deployments, the gNB may include a centralized unit (CU) and a DU. The gNB may also include an active antenna unit (AAU). The CU implements some functions of the gNB, and the DU implements some functions of the gNB. For example, the CU is responsible for processing non-real-time protocols and services, and implementing the functions of the radio resource control (RRC) and packet data convergence protocol (PDCP) layers. The DU is responsible for processing physical layer protocols and real-time services, and implementing the functions of the radio link control (RLC) layer, the media access control (MAC) layer, and the physical (PHY) layer. The AAU implements some physical layer processing functions, RF processing, and related functions of active antennas. The information of the RRC layer is generated by the CU, and will eventually be encapsulated by the PHY layer of the DU to become the PHY layer information, or, it is converted from the PHY layer information. Therefore, in this architecture, high-level signaling such as RRC layer signaling can also be considered to be sent by the DU, or, sent by the DU+AAU. It is understandable that the access network device may be a device including one or more of a CU node, a DU node, and an AAU node. In addition, the CU may be classified as an access network device in an access network (radio access network, RAN), or the CU may be classified as an access network device in a core network (core network, CN), and this application does not limit this.

[0117] 3. User plane network element 130: As the interface with the data network, it completes functions such as user plane data forwarding, session / flow-level billing statistics, bandwidth limitation, etc. That is, packet routing and forwarding, and quality of service (QoS) processing of user plane data.

[0118] In a 5G communication system, the user plane network element may be a user plane function (UPF) network element.

[0119] 4. Data network 140: provides, for example, operator services, Internet access or third-party services, including servers, which implement video source encoding, rendering, etc. In the 5G communication system, the data network can be a data network (DN).

[0120] 5. Authentication server 150: performs security authentication of the user. In the 5G communication system, the authentication server may be an authentication server function (AUSF).

[0121] 6. Mobility management network element 160: Mainly used for mobility management and access management. In the 5G communication system, the access management network element may be the access and mobility management function (AMF), which mainly performs mobility management, access authentication / authorization, etc. In addition, it is also responsible for transmitting user policies between the terminal and the policy control function (PCF) network element.

[0122] 7. Session management network element 170: mainly used for session management, allocation and management of Internet protocol (IP) addresses of user equipment, selection of endpoints of manageable user plane functions, policy control and charging function interfaces, and downlink data notification.

[0123] In the 5G communication system, the session management network element can be a session management function (SMF) network element, which completes terminal IP address allocation, UPF selection, and billing and QoS policy control.

[0124] 8. Application network element 180: In the 5G communication system, the application network element can be an application function (AF) network element, which represents the application function of a third party or an operator. It is the interface for the 5G network to obtain external application data and is mainly used to convey the requirements of the application side to the network side.

[0125] 9. Unified data management network element 190: responsible for the management of user identification, contract data, authentication data, and user service network element registration management. In the 5G communication system, the unified data management network element can be unified data management (UDM).

[0126] 10. Policy control network element 191: includes user contract data management function, policy control function, billing policy control function, quality of service (QoS) control, etc. It is a unified policy framework used to guide network behavior and provide policy rule information for control plane function network elements (such as AMF, SMF network elements, etc.).

[0127] In a 5G communication system, the policy control network element may be a PCF.

[0128] 11. Network slice selection function network element 194: responsible for selecting network slices for UE. In the 5G communication system, this application network element can be a network slice selection function (NSSF) network element.

[0129] 12. Network function repository function network element 192: Provides storage and selection functions for network function entity information for other core network elements. In the 5G communication system, this network element may be a network function repository function network element (network function repository function, NRF).

[0130] 13. Network open network element 193: In the 5G communication system, the network open network element may be a network open function (NEF) network element, which is mainly used to expose the services and capabilities of the 3GPP network function to the AF, and also allows the AF to provide information to the 3GPP network function.

[0131] In future communication systems, such as 6G communication systems, the above-mentioned network elements or devices may still use their names in 5G communication systems, or may have other names, which is not limited in the embodiments of the present application. The functions of the above-mentioned network elements or devices may be completed by an independent network element or by several network elements. In actual deployment, the network elements in the core network may be deployed on the same or different physical devices. For example, as a possible deployment, AMF and SMF may be deployed on the same physical device. For another example, the network elements of the 5G core network may be deployed on the same physical device as the network elements of the 4G core network. This is not limited in the embodiments of the present application.

[0132] Understandably, Figure 1 This is just an example and does not constitute any limitation on the protection scope of this application. Figure 1 The network elements not shown in the figure, of course, the communication method provided in the embodiment of the present application may also only include Figure 1 Some network elements are shown.

[0133] exist Figure 1 In the network architecture shown, the terminal is connected to the AMF through the N1 interface, the (R)AN is connected to the AMF through the N2 interface, and the (R)AN is connected to the UPF through the N3 interface. The UPFs are connected to each other through the N9 interface, and the UPF is interconnected with the DN through the N6 interface. The SMF controls the UPF through the N4 interface.

[0134] It can be understood that the above-mentioned network architecture applied to the embodiment of the present application is only an example, and the network architecture applicable to the embodiment of the present application is not limited to this. Any network architecture that can realize the functions of the above-mentioned network elements is applicable to the embodiment of the present application.

[0135] Figure 2 and Figure 3 This is a schematic diagram of a user dual-contract architecture provided by an embodiment of the present application. R16 uses the N3IWF architecture to support the intercommunication between SNPN and PLMN, that is, UE dual-contracts, respectively contracting to SNPN and PLMN. Figure 2 As shown, the UE accesses the PLMN through the 3GPP access type, that is, the UE accesses the PLMN through the access network device of the PLMM. The UE establishes a PDU session in the PLMN, selects the N3IWF network element of the SNPN network and establishes access to the N3IWF network element of the SNPN through the PDU session in the PLMN, and establishes an IPSec connection with the N3IWF of the SNPN, thereby accessing the SNPN through the N3GPP access type. Access through the N3GPP access type means that the UE accesses the network through the N3IWF network element with the N3GPP access type. Figure 3 and Figure 2 The difference is that the UE first accesses the SNPN through the 3GPP access type, and then accesses the PLMN through the N3GPP access type.

[0136] exist Figure 2 and Figure 3 In the scenario architecture, the network accessed by the UE through the 3GPP access type is the underlying network, also referred to as the lower network in this embodiment, and the network accessed through the N3GPP access type is also referred to as the upper network in this embodiment. Figure 2 The upper network is SNPN, the lower network is PLMN, and Figure 3 The upper network in the PN is PLMN, and the lower network is SNPN. The lower network can also be called the underlying network, and the upper network can also be called the overlay network.

[0137] Figure 2 and Figure 3 This is only an example, and the upper network and the lower network may also be other networks, or the upper network and the lower network may be the same, and this application does not impose any limitation on this.

[0138] The non-public network PNI-NPN can be implemented using network slices in the PLMN. In order to prevent unauthorized UEs from attempting to access and select the network, a closed access group (CAG) function is used. CAG can identify a group of users that are allowed to access cells associated with CAG, namely CAG cells. To prevent UEs that are not allowed to access CAG cells from automatically selecting and accessing CAG cells, the CAG cell broadcasts one or more CAG identifiers, and the UE is configured with an available CAG list and indication information, which indicates whether the UE is only allowed to access the 5G system through the CAG cell. The UE subscription data on the UDM includes the available CAG list and the indication information.

[0139] The SNPN network is deployed independently and does not rely on the PLMN network. It uses the PLMN identifier + network identifier to identify it together. The PLMN identifier can be an inherent value reserved by a third-party operator or a specific value of the PLMN operator that deploys this SNPN. In the SNPN network, its cell broadcasts the PLMN identifier + network identifier, and the UE selects the NPN network to access based on the broadcast information and the configured network selection information. If the UE finds that the configured network selection information (PLMN identifier + network identifier) ​​is different from the PLMN identifier or PLMN identifier + network identifier broadcast by the network, the UE will not select the network to access.

[0140] PLMN can support IMS voice service. In the process of UE registering to PLMN through (R)AN, AMF can determine whether voice service is supported according to local policy, UE capability, roaming agreement, whether single radio voice call continuity (SRVCC) is supported, and at least one of the voice support match indication information (Voice Support Match Indicator) provided by (R)AN, and send the indication information of whether IMS voice service can be provided over PS session accessed through 3GPP (IMS voice over PS Session Supported Indicationover 3GPP) and whether IMS voice service can be provided over PS session accessed through N3GPP (IMS voiceover PS Session Supported Indication over N3GPP) to UE, so that UE can subsequently initiate IMS voice service in PLMN network according to the indication information. If AMF does not have voice support match indication information locally, it can obtain the information from (R)AN, and (R)AN can determine the information according to local configuration and UE capability and send it to AMF.

[0141] If the indication information indicates that the PLMN does not support the IMS voice service, the voice-centric UE needs to reselect a network that can support the IMS voice service.

[0142] If the UE accesses the PLMN through N3GPP access, the AMF can directly send the UE an indication of whether it can support the provision of IMS voice services through the PS session accessed through N3GPP according to the local configuration. If the local configuration indicates that the PLMN can provide IMS voice services through N3IWF / trusted non-3GPP gateway function (TNGF), the AMF indicates that the UE can support the provision of IMS voice services through the PS session accessed through N3GPP.

[0143] exist Figure 3 In the scenario, the upper network is PLMN, which can support the provision of IMS voice services. However, when the UE initiates the IMS voice service, if the lower network does not support the IMS voice service, the UE cannot guarantee the service quality when performing the IMS voice service, and thus cannot provide the user with a normal call experience.

[0144] Figure 4 2 is a flow chart of a method 200 for selecting a network provided in an embodiment of the present application. The method 200 includes:

[0145] Step S210, the mobility management network element #1 of the first upper network obtains second indication information, where the second indication information indicates whether the first lower network can provide IMS voice services through a PS session accessed by the NR cell.

[0146] As a possible implementation method, the mobility management network element #1 of the first upper layer network receives a registration request message from the terminal device or an N2 message from the N3GPP interworking function network element, and the registration request message or the N2 message includes the second indication information, and the second indication information indicates whether the first lower layer network can provide IMS voice services through a PS session accessed by the NR cell.

[0147] As another possible implementation method, the mobility management network element #1 of the first upper layer network receives a registration request message from the terminal device or an N2 message from the N3GPP interworking function network element, and the registration request message or the N2 message includes third indication information, and the third indication information indicates whether the terminal device accesses the first upper layer network through the protocol data unit PDU session of the first lower layer network, or the third indication information indicates the network identifier of the first lower layer network.

[0148] The mobility management network element #1 of the upper network determines the second indication information according to the locally configured SLA and the third indication information.

[0149] Optionally, the local configuration of the mobility management network element #1 of the upper network also includes an identifier of the first lower network.

[0150] As another possible implementation method, SLA is configured in the N3GPP interworking function network element, and the N3GPP interworking function network element receives an IPSec message from the terminal device, the IPSec message includes a registration request message, and the IPSec message also includes third indication information, the third indication information indicates whether the terminal device accesses the first upper layer network through the protocol data unit PDU session of the first lower layer network, or the third indication information indicates the network identifier of the first lower layer network, or the N3GPP interworking function network element is a dedicated N3GPP interworking function network element, and the N3GPP interworking function network element determines the third indication information according to local configuration.

[0151] The N3GPP interworking function network element determines the second indication information according to the third indication information and the SLA, and then sends the second indication information to the mobility management network element #1 of the first upper layer network through an N2 message.

[0152] Step S220: The mobility management network element #1 of the first upper layer network determines first indication information according to the second indication information, where the first indication information indicates whether the first upper layer network can support providing IMS voice services through a PS session accessed through N3GPP.

[0153] Exemplarily, if the second indication information indicates that the first lower layer network cannot provide IMS voice services through PS sessions accessed through NR cells, the mobility management network element #1 of the first upper layer network determines the first indication information based on the second indication information, and the first indication information indicates that the first upper layer network cannot support the provision of IMS voice services through PS sessions accessed through N3GPP. If the second indication information indicates that the first lower layer network can provide IMS voice services through PS sessions accessed through NR cells, the mobility management network element #1 of the first upper layer network determines the first indication information based on the second indication information and local configuration, and the first indication information indicates whether the first upper layer network can support the provision of IMS voice services through PS sessions accessed through N3GPP.

[0154] It should be understood that when the second indication information indicates that the first lower layer network can provide IMS voice services through PS sessions accessed through the NR cell, if the mobility management network element #1 of the first upper layer network determines according to the local configuration that the first upper layer network can support IMS voice services, then the first indication information indicates that the first upper layer network can support the provision of IMS voice services through PS sessions accessed through N3GPP; if the mobility management network element #1 of the first upper layer network determines according to the local configuration that the first upper layer network cannot support IMS voice services, then the first indication information indicates that the first upper layer network cannot support the provision of IMS voice services through PS sessions accessed through N3GPP.

[0155] Step S230: The mobility management network element #1 of the first upper layer network sends the first indication information to the terminal device.

[0156] As a possible implementation manner, the mobility management network element #1 of the first upper network sends the first indication information to the terminal device via a registration response message or a NAS transmission message.

[0157] Correspondingly, the terminal device receives the first indication information. If the first indication information indicates that the first upper layer network can support the provision of IMS voice services through the PS session accessed by N3GPP, the terminal device can subsequently initiate the IMS voice service in the first upper layer network.

[0158] If the first indication information indicates that the first upper network cannot support the provision of IMS voice services through PS sessions accessed through N3GPP: The first indication information indicates that the first upper network cannot support the provision of IMS voice services through PS sessions accessed through N3GPP. There are two cases: in the first case, the first lower network supports IMS voice services, but the first upper network does not support IMS voice services. In the second case, the first lower network does not support IMS voice services, but the first upper network supports IMS voice services. In the first case, the terminal device needs to select the N3GPP interworking function network element of other upper networks that can support IMS voice services, access the upper network through the first lower network and the N3GPP interworking function network element of the upper network, or directly access the third network through the 3GPP access type, and the third network includes the first upper network. In the second case, the terminal device needs to select a second lower network that can provide IMS voice services through a PS session accessed through an NR cell, or directly access the third network through a 3GPP access type. The terminal device can distinguish the above two cases based on the first indication information.

[0159] Exemplarily, the first indication information can be indicated by 2 bits, for example, the first bit indicates whether the first upper network can support the provision of IMS voice services through the PS session accessed through N3GPP, and the second bit indicates whether the first lower network can provide IMS voice services through the PS session accessed through the NR cell. The value of the first bit is set to 1 to indicate that the first upper network can support the provision of IMS voice services through the PS session accessed through N3GPP, and the value of the first bit is set to 0 to indicate that the first upper network cannot support the provision of IMS voice services through the PS session accessed through N3GPP. The value of the second bit is set to 1 to indicate that the first lower network can provide IMS voice services through the PS session accessed through the NR cell, and the value of the second bit is set to 0 to indicate that the first lower network cannot provide IMS voice services through the PS session accessed through the NR cell. Of course, the first bit can also indicate whether the first lower network can provide IMS voice services through the PS session accessed through the NR cell, and the second bit indicates whether the first upper network can support the provision of IMS voice services through the PS session accessed through N3GPP. Or the value of the bit is set to 0 to indicate support for IMS voice services. The above is only an example, and this application does not impose any limitation on this.

[0160] pass Figure 4 According to the provided solution, the mobility management network element of the first upper-layer network can learn whether the first lower-layer network can support the IMS voice service, further determine whether the first upper-layer network can support the IMS voice service, and notify the terminal device of this information, so that the terminal device selects a network that can support the provision of the IMS voice service to initiate the IMS voice service, so as to obtain normal and guaranteed voice call quality.

[0161] Figure 5 3 is a flow chart of another network selection method 300 provided in an embodiment of the present application. The method 300 includes:

[0162] Step S310: The terminal device registers in the first lower network through the access network device.

[0163] Optionally, during this registration process, the terminal device will obtain an indication of support for providing IMS voice services over PS sessions (IMS voice over PS session support indication) sent by the first lower network to the terminal device, which indicates that the first lower network can provide IMS voice services to the terminal device through NR cells or fallback to the evolved universal terrestrial radio access network (E-UTRAN). The terminal device establishes a PDU session in the lower network and establishes an IPSec connection to the N3IWF of the target upper network through the PDU session.

[0164] Step S320: The terminal device sends a registration request message to N3IWF via an IPSec connection, and N3IWF forwards the registration request message to the mobility management network element #1 of the first upper layer network via an N2 message.

[0165] Step S330: The mobility management network element #1 of the first upper layer network determines indication information of whether it can support provision of IMS voice service through PS session accessed via N3GPP.

[0166] Exemplarily, the mobility management network element #1 of the first upper layer network determines, according to the local configuration, indication information of whether it is possible to support provision of the IMS voice service through the PS session accessed via N3GPP.

[0167] Step S340: The mobility management network element #1 of the first upper layer network sends the indication information to the terminal device. Exemplarily, the indication information may be carried in a registration response message.

[0168] It should be understood that the indication information is different from the first indication information in method 200. The indication information is determined only according to the configuration of the first upper network, while the first indication information is determined jointly according to the first lower network and the first upper network.

[0169] Step S350: The terminal device obtains second indication information. The second indication information indicates whether the first lower layer network can provide IMS voice service through the PS session accessed by the NR cell.

[0170] Specifically, the terminal device may obtain the second indication information in different ways, such as Figure 6 As shown, step S350 includes:

[0171] Step S351: The terminal device sends NR capability query information to the access network device to query whether the access network device can support providing IMS voice services through the PS session of the NR cell. For example, the NR capability query information may be an RRC NRCapability Enquiry message.

[0172] It should be understood that the terminal device can learn from step S340 that the terminal device is registered to the first upper network through the N3GPP of the first lower network, and the mobility management network element #1 of the first upper network determines according to the local configuration to support the provision of IMS voice services through the PS session accessed through N3GPP.

[0173] Step S352: The terminal device receives NR capability information sent by the access network device, and the capability information carries second indication information of whether the PS session accessed through the NR cell can support the provision of IMS voice services. For example, the NR capability information may be an RRC NR Capability Information message.

[0174] If the second indication information indicates that the PS session accessed through the NR cell cannot support the provision of IMS voice services, the terminal device selects a lower layer network that can support the provision of IMS voice services through the PS session accessed through the NR cell. If the lower layer network that can support the provision of IMS voice services through the PS session accessed through the NR cell is not successfully selected, the terminal device can also reside in a lower layer network that does not support the IMS voice service, and then create a QoS flow for IMS voice in the upper layer network, but the terminal device resides in a lower layer network that does not support the IMS voice service and cannot guarantee the service quality of the IMS voice service.

[0175] The second indication information can also be obtained by other methods, such as Figure 7 As shown, step S350 includes:

[0176] Step S351', the terminal device sends a registration request message to the mobility management network element #2 of the first lower network, and the registration request message carries an instruction to query whether the access network device can support the provision of IMS voice services through the PS session of the NR cell.

[0177] It should be understood that the terminal device can learn from step S340 that the terminal device is registered to the first upper network through the N3GPP of the first lower network, and the mobility management network element #1 of the first upper network determines according to the local configuration that the first upper network supports the provision of IMS voice services through the PS session accessed through N3GPP.

[0178] Step S357: The mobility management network element #2 of the first lower network determines the second indication information.

[0179] Exemplarily, the mobility management network element #2 of the first lower layer network determines the second indication information based on at least one of the above-mentioned indications, local configuration, terminal capabilities, voice support matching indication information, the data network name (DNN) of the terminal device session and single network slice selection assistance information (S-NSSAI).

[0180] Step S358: The mobility management network element #2 of the first lower network sends the second indication information to the terminal device.

[0181] Optionally, the mobility management network element #2 of the first lower network obtains the voice support matching indication information of the access network device of the first lower network. Exemplarily, if the mobility management network element #2 of the first lower network needs to obtain the terminal capability, the voice support matching indication information of the access network device to determine the second indication information. Then before step S357 and step S358, it also includes:

[0182] Step S352', the mobility management network element #2 of the first lower network sends a second message, the second message being used to request the access network device of the first lower network to check whether it can support the PS session accessed through the NR cell to provide an indication of the IMS voice service. For example, the indication can be carried in an N2 message, such as a UE Capability Match Request message.

[0183] Optionally, the second message may also carry the capabilities of the terminal device.

[0184] Step S353, if the second message does not carry the capabilities of the terminal device, the access network device of the first lower network sends capability query information to the terminal device, for example, the access network device sends an RRC UE Capability Enquiry message to the terminal device to request the capabilities of the terminal device.

[0185] Step S354: The terminal device sends a third message to the access network device of the first lower network, where the third message includes the capabilities of the terminal device. For example, the third message may be an RRC UE Capability Information message.

[0186] Step S355: The access network device determines the second indication information according to the local configuration and the capability of the terminal device.

[0187] Step S356: The access network device sends the second indication information to the mobility management network element #2 of the first lower network. The second indication information may be carried in the first message. For example, the first message may be a UE CapabilityMatch Request message. If the second message in step S352' does not carry the capabilities of the terminal device, the first message needs to carry the capabilities of the terminal device.

[0188] It should be noted that the second indication information determined by the access network device in the above steps, the second indication information sent to the mobility management network element #2 of the first lower network, and the second indication information sent by the mobility management network element #2 of the first lower network to the terminal device both indicate whether the first lower network can support the provision of IMS voice services through the PS session accessed through the NR cell, but the forms may be the same or different.

[0189] It should be understood that in step S350, the terminal device may also obtain the second indication information in step S310, and the obtaining method is the same as that in step S351. Figure 6 or Figure 7 This application does not impose any restrictions on the timing of the terminal device obtaining the second indication information. Figure 6 and Figure 7 They are Figure 5 In step S350 of the present invention, the terminal device obtains the second indication information in two ways, which will be described later. Figure 8-Figure 13 The steps of obtaining the second indication information by the terminal device can refer to the above Figure 6 or Figure 7 Description.

[0190] Figure 8 4 is a flow chart of another network selection method 400 provided in an embodiment of the present application. The method 400 includes:

[0191] Step S410, Figure 5 Step S310 in .

[0192] Step S420: The terminal device sends a registration request to the mobility management network element #1 of the first upper network.

[0193] Exemplarily, the terminal device sends a registration request message to N3IWF via an IPSec connection, and N3IWF forwards the registration request message to the mobility management network element #1 of the first upper network via an N2 message.

[0194] Optionally, the registration request message or N2 message carries an indication that the terminal device is registered in the first lower network, so that the mobility management network element #1 of the first upper network can learn that the terminal device accesses the N3IWF through the first lower network (through the above indication).

[0195] Optionally, the mobility management network element #1 of the first upper network can learn through a proprietary N3IWF (referring to a specific N3IWF, corresponding to a specific lower network) that the terminal device accesses the N3IWF through the first lower network.

[0196] Optionally, in step S430, the mobility management network element #1 of the first upper network sends a message to query whether the first lower network can support the provision of IMS voice services through a PS session accessed through an NR cell.

[0197] As a possible implementation, the mobility management network element #1 of the first upper network sends a NAS message to the terminal device, and the NAS message carries an indication requesting whether the first lower network supports IMS voice over PS session over NR cell. For example, the NAS message can be a registration response message or a NAS transmission message.

[0198] As another possible implementation, the mobility management network element #1 of the first upper network sends an N2 message to the N3IWF, and the N2 message carries an indication of requesting whether the first lower network supports IMS voice over PS session over NR cell. The N3IWF sends an IPSec message to the terminal device, and the IPSec message carries an indication of requesting whether the first lower network supports IMS voice over PS session over NR cell.

[0199] Step S430 is optional.

[0200] Step S440: The terminal device obtains second indication information. The second indication information indicates whether the first lower layer network can provide IMS voice service through the PS session accessed by the NR cell.

[0201] For step S440 , reference may be made to the description of step S350 .

[0202] Step S450: After the terminal device obtains the second indication information, it sends the second indication information to the mobility management network element #1 of the first upper network.

[0203] As a possible implementation manner, the second indication information may be carried in a NAS message. For example, the NAS message may be a registration request message or a NAS transmission message.

[0204] As another possible implementation, the terminal device sends an IPSec message to the N3IWF, and the IPSec message includes the second indication information. The N3IWF carries the second indication information in the N2 message and sends it to the mobility management network element #1 of the first upper network. Optionally, when the second indication information indicates that the first lower network can support the provision of IMS voice services through the PS session accessed by the NR cell, the terminal device sends the second indication information to the mobility management network element #1 of the first upper network.

[0205] Step S460: The mobility management network element #1 of the first upper network determines first indication information according to the second indication information and the local configuration. The first indication information indicates whether the first upper network can support the provision of IMS voice services through the PS session accessed through N3GPP.

[0206] Exemplarily, in the first method, the second indication information indicates that the first lower layer network can support the provision of IMS voice services through PS sessions accessed through the NR cell. If the mobility management network element #1 of the first upper layer network determines according to the local configuration that the first upper layer network does not support the IMS voice service, then the first indication information indicates that the first upper layer network cannot support the provision of IMS voice services through PS sessions accessed through N3GPP; if the mobility management network element #1 of the first upper layer network determines according to the local configuration that the first upper layer network supports the IMS voice service, then the first indication information indicates that the first upper layer network can support the provision of IMS voice services through PS sessions accessed through N3GPP.

[0207] In the second method, the second indication information indicates that the first lower layer network cannot support the provision of IMS voice services through PS sessions accessed through the NR cell. At this time, regardless of whether the mobility management network element #1 of the first upper layer network determines whether the first upper layer network supports IMS voice services based on local configuration, the first indication information indicates that the first upper layer network cannot support the provision of IMS voice services through PS sessions accessed through N3GPP.

[0208] Step S470: The mobility management network element #1 of the first upper layer network sends the first indication information to the terminal device, for example, by sending the first indication information via a registration request message or a response message of a NAS transmission message.

[0209] Optionally, if the terminal device receives first indication information indicating that the first upper layer network supports providing IMS voice services through a PS session accessed via N3GPP, the terminal device initiates an IMS voice service request in the first upper layer network.

[0210] Optionally, if the terminal device receives first indication information indicating that the first upper layer network cannot support providing IMS voice services through a PS session accessed via N3GPP, the terminal device may reselect a network.

[0211] It should be understood that the first indication information indicates that the first upper layer network cannot support the provision of IMS voice services through PS sessions accessed through N3GPP, which is divided into two situations: in the first situation, the first lower layer network supports IMS voice services, but the first upper layer network does not support IMS voice services; in the second situation, the first lower layer network does not support IMS voice services, but the first upper layer network supports IMS voice services.

[0212] If it is the first case, the terminal device needs to select the N3GPP interworking function network element of other upper-layer networks that can support IMS voice services, and access the upper-layer network through the first lower-layer network and the N3GPP interworking function network element of the upper-layer network.

[0213] In one possible implementation, the terminal device selects the N3GPP interworking function network element of the second upper network, and accesses the second upper network through the first lower network and the N3GPP interworking function network element. It should be noted that the terminal device can also execute steps S410-S470 of method 400 to obtain an indication of whether the second upper network can support the provision of IMS voice services through PS sessions accessed through N3GPP. Optionally, if the second upper network can support the provision of IMS voice services through PS sessions accessed through N3GPP, after the terminal device accesses the second upper network through the first lower network, it initiates an IMS voice service request in the second upper network.

[0214] In the second case, the terminal device needs to select a second lower layer network that can provide IMS voice services through a PS session accessed through the NR cell.

[0215] In another possible implementation, the terminal device may execute some steps of the method of this embodiment to obtain an indication of whether the second lower layer network can provide IMS voice services through a PS session accessed by an NR cell. Exemplarily, steps S410-S470 will be executed again, wherein the first lower layer network is replaced by the second lower layer network. The terminal device obtains the first indication information. Exemplarily, the terminal device may execute S440 to obtain an indication of whether the second lower layer network can provide IMS voice services through a PS session accessed by an NR cell. Optionally, the terminal device may also execute S450-S470 to send an indication of whether the second lower layer network can provide IMS voice services through a PS session accessed by an NR cell to the mobility management network element #1 of the first upper layer network to obtain the first indication information.

[0216] In another possible implementation, whether in the first case or the second case, the terminal device may also access a third network through a 3GPP access type, the third network including the first upper layer network. Optionally, the terminal device initiates an IMS voice service request in the third network.

[0217] Optionally, in the above three possible modes, the terminal device may repeat the network selection process until a lower layer network or an upper layer network that supports PS sessions accessed through NR cells is selected to provide IMS voice services.

[0218] Optionally, if, through the above another possible method, all available lower-layer networks do not support the provision of IMS voice services through the PS session accessed through the NR cell, the terminal device may choose to use the above another possible method, that is, access the first upper-layer network through the 3GPP access type. It should be understood that in step S440, the terminal device may also obtain the second indication information in step S410, and the acquisition method is the same as Figure 6 or Figure 7 , the present application does not impose any restrictions on the timing of the terminal device acquiring the second indication information. The present application does not impose any restrictions on the timing of the terminal device acquiring the first indication information and the second indication information.

[0219] Through method 400, the terminal device can select a lower layer network and an upper layer network access that can support the IMS voice service, so that the terminal device can register with the upper layer network that supports the IMS voice service, ensuring that the terminal device can subsequently initiate the IMS voice service in the upper layer network, and guaranteeing the service quality of the terminal device using the IMS voice service in the upper layer network.

[0220] Fig. 9 1 is a flow chart of another network selection method 500 provided in an embodiment of the present application. The method 500 includes:

[0221] Step S510: The terminal device initiates a registration request at the mobility management network element #2 of the first lower network, refer to step S310.

[0222] Step S520: The terminal device obtains the second indication information. The process of this step refers to step S350 and will not be repeated here.

[0223] Step S530: The terminal device sends a registration request to the mobility management network element #1 of the first upper network.

[0224] Exemplarily, the terminal device sends a registration request message to N3IWF via an IPSec connection, and N3IWF forwards the registration request message to the mobility management network element #1 of the first upper layer network via an N2 message. The registration request message or the N2 message carries the second indication information.

[0225] Optionally, the terminal device may also implicitly indicate through a registration request message that the first lower layer network can support the provision of IMS voice services through PS sessions accessed through NR cells. In other words, when the second indication information indicates that the first lower layer network can support the provision of IMS voice services through PS sessions accessed through NR cells, the terminal device sends a registration request to the mobility management network element #1 of the first upper layer network.

[0226] Step S540: The mobility management network element #1 of the first upper network determines first indication information according to the second indication information and the local configuration. The first indication information indicates whether the first upper network can support the provision of IMS voice services through the PS session accessed by N3GPP. S540 may refer to the description of S460.

[0227] Step S550: The mobility management network element #1 of the first upper layer network sends the first indication information to the terminal device, for example, by carrying the first indication information in a registration response message.

[0228] Optionally, if the terminal device receives first indication information indicating that the first upper layer network supports providing IMS voice services through a PS session accessed via N3GPP, the terminal device initiates an IMS voice service request in the first upper layer network.

[0229] Optionally, if the terminal device receives first indication information indicating that the first upper layer network cannot support providing IMS voice services through a PS session accessed via N3GPP, the terminal device may reselect a network.

[0230] The terminal device selects the N3GPP intercommunication function network element of the second upper layer network, and accesses the second upper layer network through the first lower layer network and the N3GPP intercommunication function network element; or, the terminal device accesses the third network through the 3GPP access type, and the third network includes the first upper layer network.

[0231] In one possible implementation, the terminal device selects the N3GPP interworking function network element of the second upper network, and accesses the second upper network through the first lower network and the N3GPP interworking function network element. It should be noted that the terminal device can execute some steps of the method of this embodiment, for example, steps S530-S550 of method 500, to obtain an indication of whether the second upper network can support the provision of IMS voice services through PS sessions accessed through N3GPP. Optionally, if the second upper network can support the provision of IMS voice services through PS sessions accessed through N3GPP, after the terminal device accesses the second upper network through the first lower network, it initiates an IMS voice service request in the second upper network.

[0232] In a possible implementation, if the terminal device does not select an upper layer network that can support the provision of IMS voice services through a PS session accessed via N3GPP, the terminal device can access a third network through a 3GPP access type, and the third network includes the first upper layer network.

[0233] Through method 500, the terminal device can select a lower layer network and an upper layer network access that can support the IMS voice service, so that the terminal device can register with the upper layer network that supports the IMS voice service, ensuring that the subsequent terminal device can initiate the IMS voice service in the upper layer network, and guaranteeing the service quality of the terminal device using the IMS voice service in the upper layer network.

[0234] Fig.10 6 is a flow chart of another network selection method 600 provided in an embodiment of the present application. The method 600 includes:

[0235] Step S610: The terminal device sends a registration request to the mobility management network element #1 of the first upper network.

[0236] Exemplarily, the terminal device sends a registration request message to N3IWF via an IPSec connection, and N3IWF forwards the registration request message to the mobility management network element #1 of the first upper layer network via an N2 message.

[0237] Optionally, the terminal device may carry an indication of registration through the first lower network or an identifier of the first lower network in the registration request message; or the N3IWF may carry an indication of registration through the first lower network or an identifier of the first lower network in the N2 message.

[0238] Optionally, if SLA is configured on N3IWF, N3IWF can determine the second indication information based on the locally configured SLA and carry the second indication information in the N2 message, and the second indication information indicates whether the first lower layer network can provide IMS voice services through the PS session accessed by the NR cell.

[0239] Step S620: The mobility management network element #1 of the first upper layer network determines first indication information.

[0240] As a possible implementation, the mobility management network element #1 of the first upper network may obtain the second indication information according to the SLA, thereby determining the first indication information. For example, the SLA may be configured on the mobility management network element #1 of the first upper network.

[0241] As another possible implementation, the mobility management network element #1 of the first upper network can obtain the second indication information from the N2 message, thereby determining the first indication information. Exemplarily, the SLA can be configured on the N3IWF, and the N3IWF carries the second indication information in the N2 message and sends it to the mobility management network element #1 of the first upper network.

[0242] Optionally, the mobility management network element #1 of the first upper network can obtain an indication of the terminal device registering through the first lower network or an identifier of the first lower network from the registration request or N2 message. The mobility management network element #1 of the first upper network can query the second indication information from the SLA based on the indication of the first lower network registration or the identifier of the first lower network. Step S630, the mobility management network element #1 of the first upper network sends the first indication information to the terminal device. For example, the first indication information is carried in a registration response message.

[0243] The terminal device receives the first indication information indicating that the first upper network cannot support the provision of IMS voice services through the PS session accessed through N3GPP. The terminal device selects the N3GPP interworking function network element of the second upper network, and accesses the second upper network through the first lower network and the N3GPP interworking function network element; or, the terminal device accesses a third network through the 3GPP access type, and the third network includes the first upper network.

[0244] In one possible implementation, the terminal device selects the N3GPP interworking function network element of the second upper network, and accesses the second upper network through the first lower network and the N3GPP interworking function network element. As described above, the terminal device may execute some steps of the method of this embodiment, for example, steps S610-S630 of method 600, to obtain an indication of whether the second upper network can support the provision of IMS voice services through PS sessions accessed through N3GPP. Optionally, if the second upper network can support the provision of IMS voice services through PS sessions accessed through N3GPP, after the terminal device accesses the second upper network through the first lower network, it initiates an IMS voice service request in the second upper network.

[0245] In a possible implementation, if the terminal device does not select an upper layer network that can support the provision of IMS voice services through a PS session accessed via N3GPP, the terminal device can access a third network through a 3GPP access type, and the third network includes the first upper layer network.

[0246] Through method 600, the terminal device can select a lower layer network and an upper layer network access that can support the IMS voice service, so that the terminal device can register with the network that supports the IMS voice service, ensuring that the terminal device can subsequently initiate the IMS voice service in the selected network, and guaranteeing the service quality of the terminal device using the IMS voice service.

[0247] Fig.11 700 is a flowchart of another network selection method 700 provided in an embodiment of the present application. The method 700 includes:

[0248] Step S710: The terminal device sends a registration request to the mobility management network element #1 of the first upper network.

[0249] Exemplarily, the terminal device sends a registration request message to N3IWF via an IPSec connection, and N3IWF forwards the registration request message to the mobility management network element #1 of the first upper layer network via an N2 message.

[0250] It should be understood that before step S710, the terminal device is registered in the first lower network, and the registration step is the same as S510, which will not be repeated here.

[0251] Optionally, the mobility management network element #1 of the first upper network can obtain an indication of the terminal device registering through the first lower network or an identifier of the first lower network in the registration request or N2 message.

[0252] Step S720: The mobility management network element #1 of the first upper network queries the NEF #2 of the lower network whether the first lower network can support the provision of IMS voice services through the PS session accessed through the NR cell.

[0253] Exemplarily, the mobility management network element #1 of the first upper network sends a message to the NEF #2 of the lower network to inquire whether the first lower network can support the provision of IMS voice services through the PS session accessed through the NR cell. Optionally, the message may carry an identifier of the terminal device.

[0254] Step S730, NEF#2 queries mobility management network element #2 whether the first lower layer network can support the provision of IMS voice services through the PS session accessed through the NR cell.

[0255] Optionally, if the message of step S720 carries the identifier of the terminal device, NEF#2 can learn that the mobility management network element providing services for the terminal device is mobility management network element #2. Exemplarily, NEF#2 queries UDM for the mobility management network element providing services for the terminal device. For example, NEF#2 sends a query message to UDM, and the query message carries the identifier of the terminal device. NEF#2 receives the mobility management network element fed back by UDM, for example, mobility management network element #2. Optionally, NEF#2 queries mobility management network element #2 through PCF whether the first lower layer network can support the provision of IMS voice services through PS sessions accessed through NR cells.

[0256] It should be understood that if the message of step S720 does not carry the identifier of the terminal device, NEF#2 can determine the second indication information based on the local configuration. At this time, there is no need to query the mobility management network element #2 whether the first lower layer network can support the provision of IMS voice services through the PS session accessed through the NR cell.

[0257] Step S740: The mobility management network element #2 of the first lower network determines second indication information.

[0258] Step S740 can refer to Figure 7 The description of step S357 is omitted here.

[0259] Step S750: The mobility management network element #2 of the first lower network sends second indication information to NEF #2.

[0260] Exemplarily, the mobility management network element #2 of the first lower layer network sends a response message to NEF #2 to inquire whether the first lower layer network can support the provision of IMS voice services through a PS session accessed through an NR cell, and the response message carries the second indication information.

[0261] Optionally, the mobility management network element #2 of the first lower network may send the second indication information to NEF #2 via PCF.

[0262] Step S760: NEF#2 sends second indication information to the mobility management network element #1 of the first upper network.

[0263] Exemplarily, a response message is sent to the mobility management network element #1 of the first upper layer network, and the response message carries the second indication information.

[0264] Step S770: The mobility management network element #1 of the first upper layer network determines the first indication information according to the second indication information and the local configuration. For step S770, reference may be made to the description of S460.

[0265] Step S780, the mobility management network element #1 of the first upper network sends the first indication information to the terminal device. For example, the first indication information is carried by a registration response message. Exemplarily, the mobility management network element #1 of the first upper network sends an N2 message to the N3IWF, and the N2 message includes a registration response message. The N3IWF sends an IPSec message to the terminal device to forward the registration response message.

[0266] The terminal device receives the first indication information indicating that the first upper network cannot support the provision of IMS voice services through the PS session accessed through N3GPP. The terminal device selects the N3GPP interworking function network element of the second upper network, and accesses the second upper network through the first lower network and the N3GPP interworking function network element; or, the terminal device accesses a third network through the 3GPP access type, and the third network includes the first upper network.

[0267] In one possible implementation, the terminal device selects the N3GPP interworking function network element of the second upper network, and accesses the second upper network through the first lower network and the N3GPP interworking function network element. As described above, the terminal device may execute some steps of the method of this embodiment, for example, steps S710-S780 of method 700, to obtain an indication of whether the second upper network can support the provision of IMS voice services through PS sessions accessed through N3GPP. Optionally, if the second upper network can support the provision of IMS voice services through PS sessions accessed through N3GPP, after the terminal device accesses the second upper network through the first lower network, it initiates an IMS voice service request in the second upper network.

[0268] In a possible implementation, if the terminal device does not select an upper layer network that can support the provision of IMS voice services through a PS session accessed via N3GPP, the terminal device can access a third network through a 3GPP access type, and the third network includes the first upper layer network.

[0269] Through method 700, the terminal device can select a lower layer network and an upper layer network access that can support the IMS voice service, so that the terminal device can register with the upper layer network that supports the IMS voice service, ensuring that the terminal device can subsequently initiate the IMS voice service in the upper layer network, and guaranteeing the service quality of the terminal device using the IMS voice service in the upper layer network.

[0270] Fig.12 8 is a flow chart of another network selection method 800 provided in an embodiment of the present application. The method 800 includes:

[0271] Step S810: The terminal device registers in the first lower network. S810 may refer to the description of S510, which will not be described in detail here.

[0272] Step S820, SMF#2 of the first lower network learns, based on local configuration, that the terminal device is accessing the first upper network using a PDU session of a specific DNN / S-NSSAI, thereby determining NEF#1 of the first upper network.

[0273] Step S830: SMF#2 of the first lower network sends a message to the mobility management network element #2 of the first lower network to inquire whether the first lower network can support the provision of IMS voice services through the PS session accessed through the NR cell.

[0274] Optionally, the message may carry an identifier of the terminal device.

[0275] Step S840, Figure 7 In step S357 of the first lower network, the mobility management network element #2 of the first lower network determines the second indication information and sends the second indication information to the SMF #2 of the first lower network.

[0276] Step S850: SMF#2 of the first lower network sends the second indication information to NEF#1 of the first upper network.

[0277] Optionally, after determining the second indication information, the mobility management network element #2 of the first lower network directly sends the second indication information to the NEF #1 of the first upper network. Optionally, the identifier of the terminal device may also be sent to the NEF #1 of the first upper network.

[0278] Step S860: The terminal device sends a registration request to the mobility management network element #1 of the first upper network.

[0279] Exemplarily, the terminal device sends a registration request message to N3IWF via an IPSec connection, and N3IWF forwards the registration request message to the mobility management network element #1 of the first upper network via an N2 message.

[0280] Optionally, the terminal device may carry the identifier of the first lower network in the registration request message; or the N3IWF may carry the identifier of the first lower network in the N2 message.

[0281] Optionally, the mobility management network element #1 of the first upper network determines the identifier of the first lower network through a dedicated N3IWF

[0282] Step S870: The mobility management network element #1 of the first upper network queries the NEF #1 of the first upper network whether the first lower network can support the provision of IMS voice services through the PS session accessed through the NR cell.

[0283] Exemplarily, the mobility management network element #1 of the first upper network sends a query message to the NEF #1 of the first upper network to query whether the first lower network can support the provision of IMS voice services through the PS session accessed through the NR cell. The query message carries the identifier of the first lower network.

[0284] Optionally, the query message may be forwarded to NEF#1 via the PCF of the first upper network.

[0285] Optionally, the query message also carries an identifier of the terminal device.

[0286] Step S880: NEF#1 of the first upper layer network sends a response message of the query message to mobility management network element #1, where the response message carries the second indication information.

[0287] Optionally, NEF#1 of the first upper network may directly send the second indication information to the mobility management network element #1 without querying whether the first lower network can support the provision of IMS voice services through the PS session accessed through the NR cell.

[0288] Step S890: The mobility management network element #1 of the first upper layer network determines first indication information according to the second indication information and the local configuration. The first indication information indicates whether the first upper layer network can support the provision of IMS voice services through the PS session accessed through N3GPP.

[0289] The mobility management network element #1 of the first upper layer network sends the first indication information to the terminal device, for example, by carrying the first indication information in a registration response message.

[0290] Exemplarily, in the first method, the second indication information indicates that the first lower layer network can support the provision of IMS voice services through PS sessions accessed through the NR cell. If the mobility management network element #1 of the first upper layer network determines according to the local configuration that the first upper layer network does not support the IMS voice service, then the first indication information indicates that the first upper layer network cannot support the provision of IMS voice services through PS sessions accessed through N3GPP; if the mobility management network element #1 of the first upper layer network determines according to the local configuration that the first upper layer network supports the IMS voice service, then the first indication information indicates that the first upper layer network can support the provision of IMS voice services through PS sessions accessed through N3GPP.

[0291] In the second method, the second indication information indicates that the first lower layer network cannot support the provision of IMS voice services through PS sessions accessed through the NR cell. At this time, regardless of whether the mobility management network element #1 of the first upper layer network determines whether the first upper layer network supports IMS voice services based on local configuration, the first indication information indicates that the first upper layer network cannot support the provision of IMS voice services through PS sessions accessed through N3GPP.

[0292] It should be understood that the first indication information indicates that the first upper layer network cannot support the provision of IMS voice services through PS sessions accessed through N3GPP, which is divided into two situations: in the first situation, the first lower layer network supports IMS voice services, but the first upper layer network does not support IMS voice services; in the second situation, the first lower layer network does not support IMS voice services, but the first upper layer network supports IMS voice services.

[0293] If it is the first case, the terminal device needs to select the N3GPP interworking function network element of other upper-layer networks that can support IMS voice services, and access the upper-layer network through the first lower-layer network and the N3GPP interworking function network element of the upper-layer network.

[0294] In one possible implementation, the terminal device selects the N3GPP interworking function network element of the second upper network, and accesses the second upper network through the first lower network and the N3GPP interworking function network element. It should be noted that the terminal device can execute some steps of the method of this embodiment, for example, steps S860-S890 of method 800, to obtain an indication of whether the second upper network can support the provision of IMS voice services through PS sessions accessed through N3GPP. Optionally, if the second upper network can support the provision of IMS voice services through PS sessions accessed through N3GPP, after the terminal device accesses the second upper network through the first lower network, it initiates an IMS voice service request in the second upper network.

[0295] In the second case, the terminal device needs to select a second lower layer network that can provide IMS voice services through a PS session accessed through the NR cell.

[0296] In another possible implementation, the terminal device may obtain an indication of whether the second lower layer network can provide the IMS voice service through the PS session accessed by the NR cell. Exemplarily, steps S810-S890 may be performed again, wherein the first lower layer network is replaced by the second lower layer network. The terminal device obtains the first indication information.

[0297] In another possible implementation, whether in the first case or the second case, the terminal device may also access a third network through a 3GPP access type, the third network including the first upper layer network. Optionally, the terminal device initiates an IMS voice service request in the third network.

[0298] Through method 800, the terminal device can select a lower layer network and / or upper layer network access that can support IMS voice services, so that the terminal device can register with the network that supports IMS voice services, ensuring that the terminal device can subsequently initiate IMS voice services on the network, thereby ensuring the service quality of the terminal device using the IMS voice services.

[0299] Fig.13 9 is a flow chart of another network selection method 900 provided in an embodiment of the present application. The method 900 includes:

[0300] Steps S910 to S940 are the same as steps S810 to S840 and are not described in detail here.

[0301] In step S950, the SMF#2 of the first lower layer network instructs the access network device to add second indication information in a general packet radio service tunneling protocol user plane (GTP-U) message header of one or more data packets initially sent to the terminal device, or the SMF#2 of the first lower layer network instructs the UPF#2 of the first lower layer network to add second indication information in an IPSec message header of one or more data packets sent to the terminal device.

[0302] Step S960: Send a registration request to the mobility management network element #1 of the first upper network.

[0303] Exemplarily, the terminal device sends a registration request message to N3IWF via an IPSec connection, and N3IWF forwards the registration request message to the mobility management network element #1 of the first upper network via an N2 message. The N2 message carries the second indication information. N3IWF obtains the second indication information based on the IPSec header and carries the second indication information in the N2 message.

[0304] Step S970: The mobility management network element #1 of the first upper network determines the first indication information according to the second indication information and the local configuration. The mobility management network element #1 of the first upper network sends the first indication information to the terminal device, for example, by carrying the first indication information in a registration response message.

[0305] Exemplarily, in the first method, the second indication information indicates that the first lower layer network can support the provision of IMS voice services through PS sessions accessed through the NR cell. If the mobility management network element #1 of the first upper layer network determines according to the local configuration that the first upper layer network does not support the IMS voice service, then the first indication information indicates that the first upper layer network cannot support the provision of IMS voice services through PS sessions accessed through N3GPP; if the mobility management network element #1 of the first upper layer network determines according to the local configuration that the first upper layer network supports the IMS voice service, then the first indication information indicates that the first upper layer network can support the provision of IMS voice services through PS sessions accessed through N3GPP.

[0306] In the second method, the second indication information indicates that the first lower layer network cannot support the provision of IMS voice services through PS sessions accessed through the NR cell. At this time, regardless of whether the mobility management network element #1 of the first upper layer network determines whether the first upper layer network supports IMS voice services based on local configuration, the first indication information indicates that the first upper layer network cannot support the provision of IMS voice services through PS sessions accessed through N3GPP.

[0307] It should be understood that the first indication information indicates that the first upper layer network cannot support the provision of IMS voice services through PS sessions accessed through N3GPP, which is divided into two situations: in the first situation, the first lower layer network supports IMS voice services, but the first upper layer network does not support IMS voice services; in the second situation, the first lower layer network does not support IMS voice services, but the first upper layer network supports IMS voice services.

[0308] If it is the first case, the terminal device needs to select the N3GPP interworking function network element of other upper-layer networks that can support IMS voice services, and access the upper-layer network through the first lower-layer network and the N3GPP interworking function network element of the upper-layer network.

[0309] In one possible implementation, the terminal device selects the N3GPP interworking function network element of the second upper network, and accesses the second upper network through the first lower network and the N3GPP interworking function network element. It should be noted that the terminal device can execute some steps of the method of this embodiment, for example, steps S960-S970 of method 900, to obtain an indication of whether the second upper network can support the provision of IMS voice services through PS sessions accessed through N3GPP. Optionally, if the second upper network can support the provision of IMS voice services through PS sessions accessed through N3GPP, after the terminal device accesses the second upper network through the first lower network, it initiates an IMS voice service request in the second upper network.

[0310] In the second case, the terminal device needs to select a second lower layer network that can provide IMS voice services through a PS session accessed through the NR cell.

[0311] In another possible implementation, the terminal device may obtain an indication of whether the second lower layer network can provide IMS voice services through a PS session accessed by the NR cell. Exemplarily, steps S910-S970 may be performed again, wherein the first lower layer network is replaced by the second lower layer network. The terminal device obtains the first indication information.

[0312] In another possible implementation, whether in the first case or the second case, the terminal device may also access a third network through a 3GPP access type, the third network including the first upper layer network. Optionally, the terminal device initiates an IMS voice service request in the third network.

[0313] Through method 900, the terminal device can select a lower layer network and an upper layer network access that can support IMS voice services, so that the terminal device can register with the network that supports IMS voice services, ensuring that the terminal device can subsequently initiate IMS voice services on the network, thereby ensuring the service quality of the terminal device using the IMS voice services.

[0314] It should be understood that Figure 2 to Figure 13 The sequence of the steps in the method is based on the inherent logic of the method, and the present application does not impose any limitation on the sequence of the steps in each of the above method embodiments.

[0315] It should be noted that Figure 2 to Figure 13 The execution subject illustrated in the figure is only an example. The execution subject may also be a chip, a chip system, or a processor that supports the execution subject to implement methods 200 to 900. This application does not impose any limitation on this.

[0316] The method embodiment of the present application is described above in conjunction with the drawings, and the device embodiment of the present application is described below. It can be understood that the description of the method embodiment and the description of the device embodiment can correspond to each other, so the undescribed parts can refer to the previous method embodiment.

[0317] It can be understood that in the above-mentioned method embodiments, the methods and operations implemented by the access network device can also be implemented by components (such as chips or circuits) that can be used for the access network device, and the methods and operations implemented by the core network network element or terminal can also be implemented by components (such as chips or circuits) that can be used for the core network network element or terminal.

[0318] The above mainly introduces the solution provided by the embodiment of the present application from the perspective of the interaction between various network elements. It can be understood that each network element, such as a transmitting end device or a receiving end device, includes a hardware structure and / or software module corresponding to the execution of each function in order to realize the above functions. Those skilled in the art should be aware that, in combination with the units and algorithm steps of each example described in the embodiments disclosed in this document, the present application can be implemented in the form of hardware or a combination of hardware and computer software. Whether a function is executed in the form of hardware or computer software driving hardware depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of this application.

[0319] The embodiment of the present application can divide the functional modules of the transmitting end device or the receiving end device according to the above method example. For example, each functional module can be divided corresponding to each function, or two or more functions can be integrated into one processing module. The above integrated module can be implemented in the form of hardware or in the form of software functional modules. It should be noted that the division of modules in the embodiment of the present application is schematic and is only a logical functional division. There may be other division methods in actual implementation. The following is an example of dividing each functional module corresponding to each function.

[0320] Fig.14 14 is a schematic block diagram of a communication device provided in an embodiment of the present application. The communication device 1400 includes a transceiver unit 1410 and a processing unit 1420. The transceiver unit 1410 can communicate with the outside, and the processing unit 1420 is used for data processing. The transceiver unit 1410 can also be called a communication interface or a communication unit.

[0321] Optionally, the communication device 1400 may further include a storage unit, which may be used to store instructions and / or data, and the processing unit 1420 may read the instructions and / or data in the storage unit.

[0322] In one case, the communication device 1400 can be a mobility management network element #1 of a first upper layer network, wherein the transceiver unit 1410 is used to perform the receiving or sending operations of the mobility management network element #1 in the above method embodiment, and the processing unit 1420 is used to perform the internal processing operations of the mobility management network element #1 in the above method embodiment.

[0323] In one design, the processing unit 1420 is used to obtain second indication information indicating whether the first lower layer network can provide an Internet Protocol Multimedia Network Subsystem IMS voice service through a packet switched PS session accessed by a new radio interface NR cell; the processing unit is further used to determine first indication information based on the second indication information, the first indication information indicating whether the first upper layer network can support the provision of IMS voice services through a PS session accessed by a non-third generation partnership project N3GPP;

[0324] The transceiver unit 1410 is used to send the first indication information to the terminal device.

[0325] Optionally, the transceiver unit 1410 is further used to receive a registration request message from the terminal device or an N2 message from an N3GPP interworking function network element, and the registration request message or the N2 message includes the second indication information.

[0326] Optionally, the processing unit 1420 is specifically configured to obtain the second indication information according to local configuration.

[0327] Optionally, the local configuration also includes an identifier of the first lower network.

[0328] Optionally, the transceiver unit 1410 is also used to receive a registration request message from the terminal device or an N2 message from an N3GPP interworking function network element, the registration request message or the N2 message includes third indication information, the third indication information indicates whether the terminal device accesses the first upper layer network through the protocol data unit PDU session of the first lower layer network, or the third indication information indicates the network identifier of the first lower layer network.

[0329] It should be understood that the mobility management network element #1 of the first upper network may determine the second indication information according to the locally configured SLA and the third indication information.

[0330] Optionally, SLA is configured in the N3GPP interworking function network element, and the N3GPP interworking function network element receives an IPSec message from the terminal device, and the IPSec message includes third indication information, and the third indication information indicates whether the terminal device accesses the first upper network through the protocol data unit PDU session of the first lower network, or the third indication information indicates the network identifier of the first lower network, or the N3GPP interworking function network element is a dedicated N3GPP interworking function network element, and the third indication information is determined according to the local configuration. According to the third indication information and the SLA local configuration, the second indication information is determined, and then the second indication information is sent to the transceiver unit 1410 through the N2 message.

[0331] In another case, the communication device 1400 can be the mobility management network element #2 of the first lower layer network, the transceiver unit 1410 is used to perform the receiving or sending operations of the mobility management network element #2 of the first lower layer network in the above method embodiment, and the processing unit 1420 is used to perform the internal processing operations of the mobility management network element #2 of the first lower layer network in the above method embodiment.

[0332] In one design, the processing unit 1420 is used to determine second indication information, where the second indication information indicates whether the first lower layer network can provide Internet Protocol Multimedia Network Subsystem IMS voice service through a packet switched PS session accessed by a new radio interface NR cell.

[0333] The transceiver unit 1410 is used to send the second indication information to the terminal device.

[0334] Optionally, the processing unit 1420 is specifically configured to determine the second indication information according to local configuration and capabilities of the terminal device.

[0335] Optionally, the processing unit 1420 can also determine the second indication information based on the data network name DNN of the terminal device session and the single network slice selection auxiliary information S-NSSAI.

[0336] Optionally, the transceiver unit 1410 is further used to receive a first message from an access network device of the first lower network, where the first message includes the capability of the terminal device.

[0337] Optionally, the transceiver unit 1410 is also used to send a second message to the access network device of the first lower network, where the second message is used to query whether the first lower network can provide IMS voice services through a PS session accessed by the NR cell; the transceiver unit is also used to receive second indication information from the access network device.

[0338] Optionally, the second message also includes capabilities of the terminal device.

[0339] Optionally, the second indication information from the access network device may be carried in the first message.

[0340] In one case, the communication device 1400 may be an access network device of the first lower network, or may be a chip or circuit configured in the access network device of the first lower network, which is not limited in this application. The transceiver unit 1410 is used to perform the receiving or sending operation of the access network device of the first lower network in the above method embodiment, and the processing unit 1420 is used to perform the internal processing operation of the access network device in the above method embodiment.

[0341] In one design, the processing unit 1420 is used to determine second indication information based on local configuration and terminal device capabilities, where the second indication information indicates whether the first lower layer network can provide Internet Protocol Multimedia Network Subsystem IMS voice services through a packet switched PS session accessed by a new radio interface NR cell.

[0342] The transceiver unit 1410 is configured to send the second indication information to the mobility management network element of the first lower layer network.

[0343] Optionally, the transceiver unit 1410 is also used to receive a second message from the mobility management network element of the first lower network, where the second message is used to query whether the first lower network can provide IMS voice services through a PS session accessed by the NR cell.

[0344] Optionally, the transceiver unit 1410 is further used to send a first message to the mobility management network element of the first lower network, where the first message includes the capability of the terminal device.

[0345] Optionally, the transceiver unit 1410 is further used to send capability request information to the terminal device, where the capability request information is used to request the capability of the terminal device; the transceiver unit 1410 is further used to receive a third message from the terminal device, where the third message includes the capability of the terminal device.

[0346] Optionally, the second message also includes capabilities of the terminal device.

[0347] Optionally, the communication device 1400 may be a component configured in an access network device, for example, a chip in the access network device.

[0348] In this case, the transceiver unit 1410 may be an interface circuit, a pin, etc. Specifically, the interface circuit may include an input circuit and an output circuit, and the processing unit 1420 may include a processing circuit.

[0349] Optionally, the transceiver unit 1410 may also be a radio frequency module. The processing unit 1420 may be a baseband module. The radio frequency module is mainly used for receiving and transmitting radio frequency signals and converting radio frequency signals into baseband signals; the baseband module is mainly used for baseband processing, etc.

[0350] Fig.15 15 is a schematic block diagram of another communication device provided in an embodiment of the present application. The communication device 1500 includes a transceiver unit 1510 and a processing unit 1520. The transceiver unit 1510 can communicate with the outside, and the processing unit 1520 is used for data processing. The transceiver unit 1510 can also be called a communication interface or a communication unit.

[0351] Optionally, the communication device 1500 may further include a storage unit, which may be used to store instructions and / or data, and the processing unit 1520 may read the instructions and / or data in the storage unit.

[0352] In one case, the communication apparatus 1500 may be a terminal device, and the transceiver unit 1510 is used to perform the receiving or sending operations of the terminal device in the above method embodiment.

[0353] The transceiver unit 1510 is used to receive second indication information from the mobility management network element of the first lower layer network, and the second indication information indicates that the first lower layer network can provide Internet Protocol Multimedia Network Subsystem IMS voice service through a packet switching PS session accessed by a new radio interface NR cell.

[0354] The processing unit 1520 is used to select a non-third generation partnership project access N3GPP interworking function network element of the first upper network according to the second indication information and access the first upper network through the first lower network and the N3GPP interworking function network element. The transceiver unit 1510 is also used to receive first indication information from a mobility management network element of the first upper network, and the first indication information indicates whether the first upper network can support providing IMS voice services through a PS session of N3GPP.

[0355] Optionally, the transceiver unit 1510 is also used to receive a fourth indication information from a mobility management network element of a second lower network, wherein the fourth indication information indicates that the second lower network cannot provide IMS voice services through a PS session accessed through an NR cell; the processing unit 1520 is also used to select the first lower network.

[0356] Optionally, the transceiver unit 1510 is further used to send second indication information to the mobility management network element of the first upper layer network, where the second indication information is used by the mobility management network element of the first upper layer network to determine the first indication information.

[0357] Optionally, the first indication information indicates that the first upper layer network cannot support the provision of IMS voice services through PS sessions accessed through N3GPP, and the processing unit 1520 is used to select the N3GPP intercommunication function network element of the second upper layer network, and access the second upper layer network through the first lower layer network and the N3GPP intercommunication function network element; or, the processing unit 1520 is used to access a third network through a 3GPP access type, and the third network includes the first upper layer network.

[0358] Optionally, the transceiver unit 1510 is specifically used to send a registration request message to the mobility management network element of the first upper layer network or to send an Internet security protocol message to the N3GPP intercommunication function network element of the first upper layer network, and the registration request message or the Internet security protocol message includes the second indication information.

[0359] Optionally, the transceiver unit 1510 is specifically used to send a registration request message to the mobility management network element of the first upper layer network or to send an Internet security protocol message to the N3GPP intercommunication function network element of the first upper layer network, the registration request message or the Internet security protocol message includes third indication information, the third indication information indicates whether the terminal device accesses the first upper layer network through the protocol data unit PDU session of the first lower layer network, or the third indication information indicates the network identifier of the first lower layer network.

[0360] Optionally, the device also includes a storage unit, which is used to store the first indication information; the 1520 processing unit is also used to select the N3GPP intercommunication function network element of the first upper layer network according to the first indication information.

[0361] Optionally, the processing unit 1520 is used to determine, based on the first indication information, that the first upper layer network cannot support providing IMS voice services through a PS session accessed via N3GPP; the processing unit 1520 does not select an N3GPP intercommunication function network element of the first upper layer network.

[0362] Optionally, the transceiver unit 1510 is also used to receive capability request information from an access network device of a lower-layer network, where the capability request information is used to request the capability of the terminal device; the transceiver unit 1510 is also used to send a third message to the access network device of the lower-layer network, where the third message includes the capability of the terminal device.

[0363] Optionally, the communication device 1500 may also be a component configured in a terminal device, for example, a chip in the terminal device.

[0364] In this case, the transceiver unit 1510 may be an interface circuit, a pin, etc. Specifically, the interface circuit may include an input circuit and an output circuit, and the processing unit 1520 may include a processing circuit.

[0365] Optionally, the transceiver unit 1510 may also be a radio frequency module. The processing unit 1520 may be a baseband module. The radio frequency module is mainly used for receiving and transmitting radio frequency signals and converting radio frequency signals into baseband signals; the baseband module is mainly used for baseband processing, etc.

[0366] like Fig.16As shown, the embodiment of the present application further provides a communication device 1600. The communication device 1600 includes a processor 1610, the processor 1610 is coupled to a memory 1620, the memory 1620 is used to store computer programs or instructions or and / or data, and the processor 1610 is used to execute the computer programs or instructions and / or data stored in the memory 1620, so that the method in the above method embodiment is executed.

[0367] Optionally, the communication device 1600 includes one or more processors 1610.

[0368] Alternatively, if Fig.16 As shown, the communication device 1600 may further include a memory 1620 .

[0369] Optionally, the communication device 1600 may include one or more memories 1620 .

[0370] Optionally, the memory 1620 may be integrated with the processor 1610 or provided separately.

[0371] Alternatively, if Fig.16 As shown, the communication device 1600 may further include a transceiver 1630, and the transceiver 1630 is used for receiving and / or sending signals. For example, the processor 1610 is used to control the transceiver 1630 to receive and / or send signals.

[0372] As a solution, the communication device 1600 is used to implement the operations performed by the mobility management network element #1, the mobility management network element #2, or the access network device in the above method embodiment.

[0373] For example, the processor 1610 is used to implement the processing operations performed by the mobility management network element #1, the mobility management network element #2, or the access network device in the above method embodiment, and the transceiver 1630 is used to implement the receiving or sending operations performed by the mobility management network element #1, the mobility management network element #2, or the access network device in the above method embodiment. The processing unit 1420 in the device 1400 can be Fig.16 The processor in the transceiver unit 1410 may be Fig.16 The operations performed by the processor 1610 may be specifically referred to in the above description of the processing unit 1420, and the operations performed by the transceiver 1630 may be specifically referred to in the description of the transceiver unit 1410, which will not be described in detail here.

[0374] like Fig.17As shown, the embodiment of the present application further provides a communication device 1700. The communication device 1700 includes a processor 1710, the processor 1710 is coupled to a memory 1720, the memory 1720 is used to store computer programs or instructions or and / or data, and the processor 1710 is used to execute the computer programs or instructions and / or data stored in the memory 1720, so that the method in the above method embodiment is executed.

[0375] Optionally, the communication device 1700 includes one or more processors 1710.

[0376] Alternatively, if Fig.17 As shown, the communication device 1700 may further include a memory 1720 .

[0377] Optionally, the communication device 1700 may include one or more memories 1720 .

[0378] Optionally, the memory 1720 may be integrated with the processor 1710 or provided separately.

[0379] Alternatively, if Fig.17 As shown, the communication device 1700 may further include a transceiver 1730, and the transceiver 1730 is used for receiving and / or sending signals. For example, the processor 1710 is used to control the transceiver 1730 to receive and / or send signals.

[0380] As a solution, the communication device 1700 is used to implement the operations performed by the terminal device in the above method embodiment. For example, the processor 1710 is used to implement the operations performed by the terminal device in the above method embodiment, and the transceiver 1730 is used to implement the receiving or sending operations performed by the terminal device in the above method embodiment. The processing unit 1520 in the device 1500 can be Fig.17 The processor in the transceiver unit 1510 may be Fig.17 The operations performed by the processor 1710 may be specifically referred to in the above description of the processing unit 1520, and the operations performed by the transceiver 1730 may be specifically referred to in the description of the transceiver unit 1510, which will not be described in detail here.

[0381] An embodiment of the present application also provides a computer-readable storage medium, on which computer instructions are stored for implementing the method executed by mobility management network element #1 in the above method embodiment, or the method executed by mobility management network element #2, or the method executed by an access network device or a terminal device.

[0382] For example, when the computer program is executed by a computer, the computer can implement the method executed by the core network element in the above method embodiment, or the method executed by the access network device or the terminal device.

[0383] An embodiment of the present application also provides a computer program product comprising instructions, which, when executed by a computer, enables the computer to implement the method executed by mobility management network element #1 in the above method embodiment, or the method executed by mobility management network element #2, or the method executed by an access network device or a terminal device.

[0384] The embodiment of the present application further provides a communication system, which includes the mobility management network element #2 and the access network device in the above embodiment. Optionally, the communication system also includes the mobility management network element #1 or the terminal device.

[0385] The explanation of the relevant contents and beneficial effects in any of the communication devices provided above can refer to the corresponding method embodiments provided above, and will not be repeated here.

[0386] In an embodiment of the present application, the core network element and the access network device or terminal device may include a hardware layer, an operating system layer running on the hardware layer, and an application layer running on the operating system layer. Among them, the hardware layer may include hardware such as a central processing unit (CPU), a memory management unit (MMU), and a memory (also called main memory). The operating system of the operating system layer may be any one or more computer operating systems that implement business processing through processes, such as Linux operating system, Unix operating system, Android operating system, iOS operating system, or Windows operating system. The application layer may include applications such as browsers, address books, word processing software, and instant messaging software.

[0387] The embodiments of the present application do not specifically limit the specific structure of the execution subject of the method provided in the embodiments of the present application, as long as it is possible to communicate according to the method provided in the embodiments of the present application by running a program that records the code of the method provided in the embodiments of the present application. For example, the execution subject of the method provided in the embodiments of the present application may be a core network element and an access network device or a terminal device, or a functional module in the core network element and the access network device or the terminal device that can call and execute a program.

[0388] Various aspects or features of the present application may be implemented as a method, apparatus, or article of manufacture using standard programming and / or engineering techniques. The term "article of manufacture" as used herein may encompass a computer program accessible from any computer-readable device, carrier, or medium. For example, a computer-readable medium may include, but is not limited to, a magnetic storage device (e.g., a hard disk, a floppy disk, or a magnetic tape, etc.), an optical disk (e.g., a compact disc (CD), a digital versatile disc (DVD), etc.), a smart card, and a flash memory device (e.g., an erasable programmable read-only memory (EPROM), a card, a stick, or a key drive, etc.).

[0389] The various storage media described herein may represent one or more devices and / or other machine-readable media for storing information. The term "machine-readable medium" may include, but is not limited to, wireless channels and various other media capable of storing, containing and / or carrying instructions and / or data.

[0390] It is understood that the processor mentioned in the embodiments of the present application may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or the processor may be any conventional processor, etc.

[0391] It can also be understood that the memory mentioned in the embodiments of the present application can be a volatile memory or a non-volatile memory, or can include both volatile and non-volatile memories. Among them, the non-volatile memory can be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory can be a random access memory (RAM). For example, RAM can be used as an external cache. By way of example and not limitation, RAM may include the following forms: static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous link dynamic random access memory (SLDRAM), and direct rambus RAM (DR RAM).

[0392] It should be noted that when the processor is a general-purpose processor, DSP, ASIC, FPGA or other programmable logic device, discrete gate or transistor logic device, discrete hardware component, the memory (storage module) can be integrated into the processor.

[0393] It should also be noted that the memory described herein is intended to include, but is not limited to, these and any other suitable types of memory.

[0394] Those of ordinary skill in the art will appreciate that the units and steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of protection of this application.

[0395] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described devices and units can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0396] In the several embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0397] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0398] In addition, each functional unit in each embodiment of the present application may be integrated into one unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0399] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the process or function described in the embodiment of the present invention is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. For example, the computer can be a personal computer, a server, or a network device, etc. The computer instructions can be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium, for example, the computer instructions can be transmitted from a website site, computer, server or data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line) or wireless (e.g., infrared, wireless, microwave, etc.) mode to another website site, computer, server or data center. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that contains one or more available media integrations. The available medium may be a magnetic medium (e.g., a floppy disk, a hard disk, a magnetic tape), an optical medium, or a semiconductor medium (e.g., a solid state disk (SSD)). For example, the aforementioned available medium may include, but is not limited to, various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0400] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A network selection method, characterized in that: The method comprises: The mobility management network element of the first upper layer network obtains second indication information, where the second indication information indicates whether the first lower layer network can provide an Internet Protocol Multimedia Network Subsystem IMS voice service through a packet switched PS session accessed by a new radio interface NR cell; The mobility management network element of the first upper layer network determines first indication information according to the second indication information, where the first indication information indicates whether the first upper layer network can support providing IMS voice services through a PS session accessed by a non-third generation partnership project N3GPP; The mobility management network element of the first upper layer network sends the first indication information to the terminal device.

2. The method according to claim 1, characterized in that The mobility management network element of the first upper layer network acquires the second indication information including: The mobility management network element of the first upper layer network receives a registration request message from the terminal device or an N2 message from an N3GPP interworking function network element, and the registration request message or the N2 message includes the second indication information.

3. The method according to claim 1, characterized in that: The method further comprises: The mobility management network element of the first upper layer network receives a registration request message from the terminal device or an N2 message from the N3GPP interworking function network element, and the registration request message or the N2 message includes third indication information, and the third indication information indicates whether the terminal device accesses the first upper layer network through the protocol data unit PDU session of the first lower layer network, or the third indication information indicates the network identifier of the first lower layer network.

4. The method according to claim 1, characterized in that: The mobility management network element of the first upper layer network acquires the second indication information including: The mobility management network element of the first upper layer network obtains the second indication information according to local configuration.

5. The method according to claim 4, characterized in that The local configuration also includes an identification of the first lower network.

6. A network selection method, characterized in that: The method comprises: The mobility management network element of the first lower layer network determines second indication information, where the second indication information indicates whether the first lower layer network can provide an Internet Protocol Multimedia Network Subsystem IMS voice service through a packet switched PS session accessed by a new radio interface NR cell, and the second indication information is used to determine the first indication information, where the first indication information indicates whether the first upper layer network can support the provision of an IMS voice service through a packet switched PS session accessed by a non-third generation partnership project N3GPP; The mobility management network element of the first lower network sends the second indication information to the terminal device.

7. The method according to claim 6, characterized in that The mobility management network element of the first lower network determines the second indication information including: The mobility management network element of the first lower network determines the second indication information according to the local configuration and the capability of the terminal device.

8. The method according to claim 7, characterized in that The method further comprises: The mobility management network element of the first lower network receives a first message from an access network device of the first lower network, where the first message includes the capability of the terminal device.

9. The method according to claim 6, characterized in that The method further comprises: The mobility management network element of the first lower network sends a second message to the access network device of the first lower network, where the second message is used to query whether the first lower network can provide an IMS voice service through a PS session accessed by the NR cell; The mobility management network element of the first lower layer network receives the second indication information from the access network device.

10. The method according to claim 9, characterized in that The second message also includes the capabilities of the terminal device.

11. A method for network selection, characterized in that: The method comprises: The terminal device receives second indication information from the mobility management network element of the first lower network, where the second indication information indicates that the first lower network can provide an Internet Protocol Multimedia Network Subsystem IMS voice service through a packet switched PS session accessed by a new radio interface NR cell; The terminal device selects a non-third generation partnership project access N3GPP interworking function network element of the first upper network according to the second indication information, and accesses the first upper network through the first lower network and the N3GPP interworking function network element; The terminal device receives first indication information from a mobility management network element of the first upper layer network, where the first indication information indicates whether the first upper layer network can support providing IMS voice services through a PS session of N3GPP.

12. The method according to claim 11, characterized in that The method further comprises: The terminal device receives fourth indication information from a mobility management network element of a second lower network, where the fourth indication information indicates that the second lower network cannot provide an IMS voice service through a PS session accessed by an NR cell; The terminal device selects the first lower network.

13. The method according to claim 11, characterized in that The method further comprises: The terminal device sends the second indication information to the mobility management network element of the first upper layer network, and the second indication information is used by the mobility management network element of the first upper layer network to determine the first indication information.

14. The method according to any one of claims 11 to 13, characterized in that The first indication information indicates that the first upper layer network cannot support providing an IMS voice service through a PS session accessed through N3GPP, and the method further includes: The terminal device selects an N3GPP interworking function network element of a second upper network, and accesses the second upper network through the first lower network and the N3GPP interworking function network element; or, The terminal device accesses a third network through a 3GPP access type, and the third network includes the first upper layer network.

15. The method according to claim 14, characterized in that The terminal device sending the second indication information to the mobility management network element of the first upper network includes: The terminal device sends a registration request message to the mobility management network element of the first upper layer network or sends an Internet security protocol message to the N3GPP interworking function network element of the first upper layer network, and the registration request message or the Internet security protocol message includes the second indication information.

16. The method according to claim 11, characterized in that The method further comprises: The terminal device sends a registration request message to the mobility management network element of the first upper layer network or sends an Internet security protocol message to the N3GPP interworking function network element of the first upper layer network, and the registration request message or the Internet security protocol message includes third indication information, and the third indication information indicates whether the terminal device accesses the first upper layer network through the protocol data unit PDU session of the first lower layer network, or the third indication information indicates the network identifier of the first lower layer network.

17. The method according to claim 11, characterized in that The method further comprises: The terminal device stores the first indication information; The terminal device selects the N3GPP intercommunication function network element of the first upper layer network according to the first indication information.

18. The method according to claim 17, characterized in that The terminal device selects the N3GPP interworking function network element of the first upper layer network according to the first indication information, including: The terminal device determines, according to the first indication information, that the first upper layer network cannot support provision of an IMS voice service through a PS session accessed through N3GPP; The terminal device does not select the N3GPP intercommunication function network element of the first upper layer network.

19. The method according to any one of claims 11 to 13, 15 to 18, characterized in that The method further comprises The terminal device receives capability request information from the access network device of the first lower network, where the capability request information is used to request the capability of the terminal device; The terminal device sends a third message to the access network device of the first lower network, and the third message includes the capability of the terminal device.

20. A method for network selection, characterized in that: The method comprises: The access network device of the first lower network determines the second indication information according to the local configuration and the capability of the terminal device, wherein the second indication information indicates whether the first lower network can provide an Internet Protocol Multimedia Network Subsystem IMS voice service through a packet switched PS session accessed by a new radio interface NR cell, and the second indication information is used to determine the first indication information, wherein the first indication information indicates whether the first upper network can support the provision of IMS voice services through a packet switched PS session accessed by a non-third generation partnership project N3GPP; The access network device of the first lower network sends the second indication information to the mobility management network element of the first lower network.

21. The method according to claim 20, characterized in that The method further comprises: The access network device of the first lower network receives a second message from the mobility management network element of the first lower network, where the second message is used to query whether the first lower network can provide IMS voice services through a PS session accessed by an NR cell.

22. The method according to claim 20 or 21, characterized in that The method further comprises: The access network device of the first lower network sends a first message to the mobility management network element of the first lower network, where the first message includes the capability of the terminal device.

23. The method according to claim 22, characterized in that The method further comprises: The access network device of the first lower network sends capability request information to the terminal device, where the capability request information is used to request the capability of the terminal device; The access network device of the first lower network receives a third message from the terminal device, where the third message includes the capability of the terminal device.

24. The method according to claim 21, characterized in that The second message also includes the capabilities of the terminal device.

25. A network selection device, characterized in that: The device comprises: A processing unit, configured to obtain second indication information, where the second indication information indicates whether the first lower layer network can provide an Internet Protocol Multimedia Network Subsystem IMS voice service through a packet switched PS session accessed by a new radio interface NR cell; The processing unit is further configured to determine first indication information according to the second indication information, wherein the first indication information indicates whether the first upper layer network can support providing IMS voice services through a PS session accessed by a non-third generation partnership project N3GPP; A transceiver unit is used to send the first indication information to the terminal device.

26. The device according to claim 25, characterized in that The transceiver unit is also used to receive a registration request message from the terminal device or an N2 message from an N3GPP interworking function network element, and the registration request message or the N2 message includes the second indication information.

27. The device according to claim 25, characterized in that The transceiver unit is also used to receive a registration request message from the terminal device or an N2 message from an N3GPP interworking function network element, wherein the registration request message or the N2 message includes third indication information, and the third indication information indicates whether the terminal device accesses the first upper layer network through a protocol data unit PDU session of the first lower layer network, or the third indication information indicates a network identifier of the first lower layer network.

28. The device according to claim 25, characterized in that The processing unit is specifically configured to obtain the second indication information according to local configuration.

29. The device according to claim 28, characterized in that The local configuration also includes an identification of the first lower network.

30. A network selection device, characterized in that: The device comprises: a processing unit, configured to determine second indication information, wherein the second indication information indicates whether the first lower layer network can provide an Internet Protocol Multimedia Network Subsystem IMS voice service through a packet switched PS session accessed by a new radio interface NR cell, and the second indication information is used to determine first indication information, wherein the first indication information indicates whether the first upper layer network can support the provision of an IMS voice service through a packet switched PS session accessed by a non-third generation partnership project N3GPP; A transceiver unit is used to send the second indication information to the terminal device.

31. The device according to claim 30, characterized in that The processing unit is specifically configured to determine the second indication information according to the local configuration and the capability of the terminal device.

32. The device according to claim 31, characterized in that The transceiver unit is also used to receive a first message from an access network device of the first lower network, where the first message includes the capability of the terminal device.

33. The device according to claim 30, characterized in that The transceiver unit is further used to send a second message to the access network device of the first lower network, where the second message is used to query whether the first lower network can provide IMS voice services through the PS session accessed by the NR cell; The transceiver unit is further configured to receive the second indication information from the access network device.

34. The device according to claim 33, characterized in that The second message also includes the capabilities of the terminal device.

35. A network selection device, characterized in that: The device comprises: A transceiver unit, configured to receive second indication information from a mobility management network element of a first lower layer network, wherein the second indication information indicates that the first lower layer network can provide an Internet Protocol Multimedia Network Subsystem IMS voice service through a packet switched PS session accessed by a new radio interface NR cell; A processing unit, configured to select a non-third generation partnership project access N3GPP interworking function network element of a first upper network according to the second indication information, and access the first upper network through the first lower network and the N3GPP interworking function network element; The transceiver unit is further used to receive first indication information from the mobility management network element of the first upper layer network, where the first indication information indicates whether the first upper layer network can support providing IMS voice services through a PS session of N3GPP.

36. The device according to claim 35, characterized in that The transceiver unit is further configured to receive fourth indication information from a mobility management network element of a second lower network, wherein the fourth indication information indicates that the second lower network cannot provide an IMS voice service through a PS session accessed by an NR cell; The processing unit is further configured to select the first lower layer network.

37. The device according to claim 35, characterized in that The transceiver unit is further used to send the second indication information to the mobility management network element of the first upper network, and the second indication information is used by the mobility management network element of the first upper network to determine the first indication information.

38. The device according to any one of claims 35 to 37, characterized in that The first indication information indicates that the first upper network cannot support the provision of IMS voice services through the PS session accessed through N3GPP, and the processing unit is used to select an N3GPP interworking function network element of the second upper network, and access the second upper network through the first lower network and the N3GPP interworking function network element; or, The processing unit is used to access a third network through a 3GPP access type, and the third network includes the first upper layer network.

39. The device according to claim 38, characterized in that The transceiver unit is specifically used to send a registration request message to the mobility management network element of the first upper layer network or send an Internet security protocol message to the N3GPP interworking function network element of the first upper layer network, and the registration request message or the Internet security protocol message includes the second indication information.

40. The device according to claim 35, characterized in that The transceiver unit is specifically used to send a registration request message to the mobility management network element of the first upper layer network or to send an Internet security protocol message to the N3GPP interworking function network element of the first upper layer network, the registration request message or the Internet security protocol message includes third indication information, the third indication information indicates whether the terminal device accesses the first upper layer network through the protocol data unit PDU session of the first lower layer network, or the third indication information indicates the network identifier of the first lower layer network.

41. The device according to claim 35, characterized in that The device also includes: A storage unit, used for storing the first indication information; The processing unit is further used to select an N3GPP interworking function network element of the first upper layer network according to the first indication information.

42. The device according to claim 41, characterized in that The processing unit is used to determine, according to the first indication information, that the first upper layer network cannot support the provision of IMS voice services through the PS session accessed through N3GPP; The processing unit does not select the N3GPP interworking function network element of the first upper layer network.

43. The device according to any one of claims 35 to 37 and 39 to 42, characterized in that The transceiver unit is further used to receive capability request information from the access network device of the first lower network, wherein the capability request information is used to request the capability of the terminal device; The transceiver unit is further used to send a third message to the access network device of the first lower network, and the third message includes the capability of the terminal device.

44. A network selection device, characterized in that: The device comprises: a processing unit, configured to determine second indication information according to a local configuration and a capability of a terminal device, wherein the second indication information indicates whether the first lower layer network can provide an Internet Protocol Multimedia Network Subsystem IMS voice service through a packet switched PS session accessed by a new radio interface NR cell, and the second indication information is used to determine first indication information, wherein the first indication information indicates whether the first upper layer network can support the provision of an IMS voice service through a packet switched PS session accessed by a non-third generation partnership project N3GPP; A transceiver unit is used to send the second indication information to the mobility management network element of the first lower network.

45. The device according to claim 44, characterized in that The transceiver unit is also used to receive a second message from the mobility management network element of the first lower network, where the second message is used to query whether the first lower network can provide IMS voice services through a PS session accessed by the NR cell.

46. ​​The device according to claim 44 or 45, characterized in that The transceiver unit is also used to send a first message to the mobility management network element of the first lower network, and the first message includes the capability of the terminal device.

47. The device according to claim 46, characterized in that The transceiver unit is further used to send capability request information to the terminal device, where the capability request information is used to request the capability of the terminal device; The transceiver unit is further configured to receive a third message from the terminal device, wherein the third message includes the capability of the terminal device.

48. The device according to claim 45, characterized in that The second message also includes the capabilities of the terminal device.

49. A network selection device, characterized in that: The method comprises a processor coupled to a memory, the memory being used to store a computer program or an instruction, the processor being used to execute the computer program or the instruction in the memory, so that the network selected device executes the method according to any one of claims 1 to 5, or executes the method according to any one of claims 6 to 10, or executes the method according to any one of claims 11 to 19, or executes the method according to any one of claims 20 to 24.

50. A chip system, characterized in that: include: A processor, used to call and run a computer program from a memory so that a communication device equipped with the chip system executes a method as described in any one of claims 1 to 5, or executes a method as described in any one of claims 6 to 10, or executes a method as described in any one of claims 11 to 19, or executes a method as described in any one of claims 20 to 24.

51. A computer-readable storage medium, characterized in that: A computer program or instruction is stored, and when the computer program or instruction is executed, the computer executes the method as claimed in any one of claims 1 to 5, or the method as claimed in any one of claims 6 to 10, or the method as claimed in any one of claims 11 to 19, or the method as claimed in any one of claims 20 to 24.

52. A computer program product, comprising a computer program, which, when executed on a computer, enables the computer to execute the method as claimed in any one of claims 1 to 5, or the method as claimed in any one of claims 6 to 10, or the method as claimed in any one of claims 11 to 19, or the method as claimed in any one of claims 20 to 24.

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