Patent Description:
To address challenges from wireless broadband technologies and maintain a pioneering advantage of 3rd generation partnership project (3rd generation partnership project, 3GPP) networks, the 3GPP standard organization formulated a network architecture of a next generation mobile communications system (next generation system), which is referred to as a 5th generation (5th generation, <NUM>) network architecture, at the end of <NUM>. This architecture not only supports a wireless technology defined in the 3GPP standard organization in accessing a <NUM> core network (<NUM> core network), but also supports a non-3GPP (non-3GPP) access technology in accessing a <NUM> core network.

Currently, when a terminal needs to access a <NUM> core network, usually, after receiving an access network discovery information request from the terminal, an access network discovery and selection function (access network discovery and selection function, ANDSF) entity sends a correspondence between terminal location information and an access network type to the terminal, and the terminal selects, based on the correspondence and a current location of the terminal, a 3GPP network or a non-3GPP network for access. However, the method for selecting an access network type is not flexible, and consequently, the selected access network type may be inappropriate. Therefore, how to flexibly select an access network type is an urgent problem to be resolved currently.

In <CIT>, in a case where the UE currently uses only the 3GPP access network and the 3GPP access network currently in use is in a congestion/overload situation and there is a WLAN(s) that can be used by the UE at a current location (in addition, the WLAN(s) is not in the congestion/overload situation), a Packet Data Network Gateway may allow to use not the 3GPP access network but the WLAN access network as to an IP flow#<NUM> of the UE.

In description of this application, "/" means "or" unless otherwise specified. For example, A/B may represent A or B. In this specification, "and/or" describes only an association relationship for describing associated objects and represents that three relationships may exist. In addition, in the descriptions of this application, "a plurality of" means two or more than two.

A network architecture and a service scenario described in the embodiments of this application are intended to describe the technical solutions in the embodiments of this application more clearly, and do not constitute a limitation on the technical solutions provided in the embodiments of this application. A person of ordinary skill in the art may know that with evolution of the network architecture and emergence of new service scenarios, the technical solutions provided in the embodiments of this application are also applicable to similar technical problems.

<FIG> shows a communications system <NUM> according to an embodiment of this application. The communications system <NUM> may be used for selection of an access network type. The communications system <NUM> includes a policy control function (policy control function, PCF) entity <NUM> and a session management function (session management function, SMF) entity <NUM>.

The PCF entity <NUM> is configured to: send an access network type corresponding to a second network to the SMF entity <NUM> after determining that a network status of a first network does not meet a preset condition, where the access network type corresponding to the second network is used to instruct a terminal to redirect a session of the terminal to the second network, and the second network is a network other than the first network.

The SMF entity <NUM> is configured to: receive the access network type corresponding to the second network from the PCF entity <NUM>, and send the access network type corresponding to the second network to the terminal.

It should be noted that the PCF entity <NUM> and the SMF entity in <FIG> may directly communicate with each other, or may communicate with each other by forwarding by another network device. This is not specifically limited in this embodiment of this application.

For example, the system <NUM> for selecting an access network type may be applied to a <NUM> network and a future network. This is not specifically limited in this embodiment of this application.

If the system <NUM> for selecting an access network type is applied to a <NUM> network, as shown in <FIG>, the <NUM> network may further include an access network (access network, AN) device, a unified data management (unified data management, UDM) entity, an access and mobility management function (Access and Mobility Management Function, AMF) entity, and a user plane function (User Plane Function, UPF) entity.

For example, the terminal communicates with the AMF entity by using a next generation network (Next generation, N) interface <NUM> (N1 for short), the AN device communicates with the AMF entity by using an N interface <NUM> (N2 for short), the AN device communicates with the UPF entity by using an N interface <NUM> (N3 for short), the AMF entity communicates with the UDM entity by using an N interface <NUM> (N8 for short), the AMF entity communicates with the SMF entity by using an N interface <NUM> (N11 for short), the AMF entity communicates with the PCF entity by using an N interface <NUM> (N15 for short), the SMF entity communicates with the PCF entity by using an N interface <NUM> (N7 for short), and the SMF entity communicates with the UPF entity by using an N interface <NUM> (N4 for short).

The terminal (terminal) in this embodiment of this application may include various handheld devices, vehicle-mounted devices, wearable devices, or computing devices that have a wireless communication function, or another processing device connected to a wireless modem. The terminal may also be referred to as user equipment (user equipment, UE), a mobile station (mobile station, MS), or a terminal device (terminal device), or may further include a subscriber unit (subscriber unit), a cellular phone (cellular phone), a smartphone (smart phone), a wireless data card, a personal digital assistant (personal digital assistant, PDA) computer, a tablet computer, a wireless modem (modem), a handheld (handheld) device, a laptop computer (laptop computer), a cordless phone (cordless phone), a wireless local loop (wireless local loop, WLL) station, a machine type communication (machine type communication, MTC) terminal, or the like.

The AN device in this embodiment of this application is an apparatus that is deployed in a radio access network and that is configured to provide a wireless communication function to a terminal. The AN device may include base stations in various forms, such as a macro base station, a micro base station (also referred to as a small cell), a relay station, and an access point. In systems that use different radio access technologies, devices having a base station function may have different names. For example, in a long term evolution (long term evolution, LTE) system, the device is referred to as an evolved NodeB (evolved NodeB, eNB or eNodeB), and in a 3rd generation (3rd Generation, <NUM>) system, the device is referred to as a NodeB (Node B).

The AMF entity in this embodiment of this application is responsible for functions such as registration management, mobility management, and lawful interception.

For functions of the SMF entity and the PCF entity in this embodiment of this application, refer to the descriptions in <FIG>. In addition, the SMF entity is further configured to perform session management, including session establishment, session modification, session release, and sessionrelated control functions such as assignment and management of an IP address of the terminal, selection and control of the UPF entity, and lawful interception. The PCF entity further provides a policy rule, and supports policy-related functions such as unified policy architecture management network behavior.

The UPF entity in this embodiment of this application may be responsible for processing functions such as forwarding and statistics collection of a packet of the terminal. For example, the UPF entity may implement user plane functions of a serving gateway (serving gateway, SGW) and a packet data network gateway (packet data network gateway, PGW). The UPF entity may alternatively be a software defined network (software defined network, SDN) switch (Switch).

The UDM entity in this embodiment of this application is configured to store subscription data. In addition, the UDM entity further includes functions such as authentication, subscriber identifier processing, and subscription management.

Although not shown, the <NUM> network may further include an authentication server function (authentication server function, AUSF) entity, a data storage function (data storage function, DSF) entity, and the like. This is not specifically limited in this embodiment of this application.

It should be noted that the terminal, the AN device, the AMF entity, the SMF entity, the UDM entity, the UPF entity, and the PCF entity in the <NUM> network are only names. The names do not constitute a limitation on devices themselves. In the <NUM> network and the another future network, network elements or entities corresponding to the terminal, the AN device, the AMF entity, the SMF entity, the UDM entity, the UPF entity, and the PCF entity may have other names. This is not specifically limited in this embodiment of this application. For example, the UDM entity may be replaced with a home subscriber server (home subscriber server, HSS), a user subscription database (user subscription database, USD), or a database entity. Uniform descriptions are provided herein, and details are not described below again.

<FIG> is a schematic flowchart of a method for selecting an access network type according to an embodiment of this application. The method relates to interaction between a terminal, a PCF entity, and an SMF entity.

The PCF entity determines that a network status of a first network does not meet a preset condition. The first network is a network currently accessed by the terminal.

That the network status of the first network does not meet the preset condition refers to: A quota of the first network does not meet the preset condition. As an example not covered by the invention, that the network status of the first network does not meet the preset condition may refer to: A congestion status of the first network does not meet a preset condition. The congestion status includes being congested or not being congested.

The PCF entity sends an access network type corresponding to a second network to the SMF entity. Correspondingly, the SMF entity receives the access network type corresponding to the second network from the PCF entity. The access network type corresponding to the second network is used to instruct the terminal to redirect a session of the terminal to the second network, and the second network is a network other than the first network.

The SMF entity sends the access network type corresponding to the second network to the terminal. Correspondingly, the terminal receives the access network type corresponding to the second network from the SMF entity.

The terminal redirects the session of the terminal to the second network based on the access network type corresponding to the second network.

In the method for selecting an access network type provided in this embodiment of this application, a network side may select the access network type based on the network status of the network, and redirect the session of the terminal from the first network to the second network when the network status of the first network does not meet the preset condition. In other words, control by the network side over selection of the access network type by the terminal is enhanced, and the access network type is more flexibly selected by the terminal. Therefore, a problem in the prior art that a selected access network type is inappropriate because network access is selected based on a current location of a terminal, and consequently, subsequent communication efficiency may be reduced can be avoided to some extent.

The following uses an example in which the system <NUM> for selecting an access network type shown in <FIG> is applied to the <NUM> network shown in <FIG>, to describe, with reference to <FIG>, the method for selecting an access network type shown in <FIG>.

<FIG> and <FIG> show a method for selecting an access network type according to an embodiment of this application. The following describes the method by using an example in which the method for selecting an access network type is applied to a packet data unit (packet data unit, PDU) session establishment procedure. For example, the method relates to interaction between a terminal, a device <NUM>, a device <NUM>, an AMF entity, a UPF entity <NUM>, a UPF entity <NUM>, an SMF entity, a PCF entity, and a UDM entity.

The terminal sends a non-access stratum (non access stratum, NAS) message to the AMF entity. Correspondingly, the AMF entity receives the NAS message from the terminal. The NAS message includes a PDU session (session) identifier (identity, ID) and N1 session management (session management, SM) information (information), and the N1 SM information includes a PDU session establishment request (PDU session establishment request) message.

In addition, the NAS message may further include other information, for example, single network slice selection assistance information (single network slice selection assistance information, S-NSSAI) and a data network name (Data Network Name, DNN). This is not specifically limited in this embodiment of this application.

The AMF entity determines, based on the PDU session identifier, to establish a new PDU session.

The AMF entity selects the SMF entity.

For a specific implementation in which the AMF entity selects the SMF entity, refer to the prior art.

The AMF entity sends an SM request <NUM> to the SMF entity. Correspondingly, the SMF entity receives the SM request <NUM> from the AMF entity. The SM request <NUM> includes the N1 SM information and a current access network type (access technology type).

In addition, the SM request <NUM> may further include other information, such as a subscription parameter (subscriber parameter) identifier, a DNN, S-NSSAI, a PDU session identifier, an AMF identifier, and user location information (user location information). This is not specifically limited in this embodiment of this application.

The SMF entity selects the PCF entity.

For a specific implementation in which the SMF entity selects the PCF entity, refer to the prior art.

The SMF entity sends a PDU-connectivity access network (connectivity access network, CAN) session establishment request to the PCF entity. Correspondingly, the PCF entity receives the PDU-CAN session establishment request from the SMF entity. The PDU-CAN session establishment request includes user location information and the current access network type.

Optionally, in this embodiment of this application, the PCF entity may send a terminal location request to the SMF entity or the AMF entity. Correspondingly, after receiving the terminal location request from the PCF entity, the SMF entity sends the user location information to the PCF entity. A network element from which the PCF entity obtains the user location information is not limited in this embodiment of this application.

The user location information in this embodiment of this application may also be referred to as terminal location information. Uniform descriptions are provided herein, and details are not described below again.

The PCF entity determines that the network status of the first network does not meet the preset condition, where the first network is a network currently accessed by the terminal, that is, a network corresponding to the current access network type.

The network status in this embodiment of this application includes at least one of a congestion status or a quota. The congestion status includes being congested or not being congested. The quota (Quota) refers to traffic that can be used by a user in a specified period or in a session.

If the network status includes a congestion status, that the network status of the first network does not meet the preset condition specifically means that the first network is congested.

If the network status includes a quota, that the network status of the first network does not meet the preset condition specifically means that traffic that can be used by the user in a specified period or in a session does not meet a user requirement.

Optionally, the PCF entity may query the network status of the first network in the PCF entity in real time after receiving the PDU-CAN session establishment request, or may periodically query the network status of the first network after receiving the PDU-CAN session establishment request. This is not specifically limited in this embodiment of this application.

The PCF entity sends a request message to the UDM entity. Correspondingly, the UDM entity receives the request message from the PCF entity. The request message includes the user location information and is used to request access network type information for a current location of the terminal.

The UDM entity sends a response message to the PCF entity. Correspondingly, the PCF entity receives the response message from the UDM entity. The response message includes the access network type information for the current location of the terminal.

The PCF entity learns, based on the access network type information for the current location of the terminal, that a second network covers the current location of the terminal, where the second network is a network, other than the first network, in networks that cover the current location of the terminal.

For example, the first network may be a 3GPP network, and the second network may be a non-3GPP network.

Optionally, the access network type information that is of the current location of the terminal and that is included in the response message in step S409 may include an access network type corresponding to the first network and an access network type corresponding to the second network, or may include only an access network type corresponding to the second network. This is not specifically limited in this embodiment of this application, and only that the PCF entity learns, based on the access network type information for the current location of the terminal, that the second network covers the current location of the terminal needs to be limited. In other words, the PCF only needs to learn of access network type information of a network, other than the first network, that covers the current location of the terminal.

Steps S408 to S410 provide a specific implementation in which the PCF entity learns that the second network covers the current location of the terminal. Optionally, the PCF entity may further learn, in another manner, that the second network covers the current location of the terminal. For example, the PCF entity learns, by interacting with the terminal, that the second network covers the current location of the terminal. Specifically, the PCF entity sends a request message to the terminal. The request message is used to request the access network type information for the current location of the terminal. Then, the terminal sends a response message to the PCF entity. The response message includes the access network type information for the current location of the terminal. Then, the PCF entity learns, based on the access network type information for the current location of the terminal, that the second network covers the current location of the terminal. The case is not specifically limited in this embodiment of this application. In this case, the PDU-CAN session establishment request message in step S406 may not include the user location information.

The PCF entity obtains a network status of the second network.

Optionally, in this embodiment of this application, the PCF may exist as a common network element in the first network and the second network. In this case, after learning that the second network covers the current location of the terminal, the PCF entity may query the network status of the second network in the PCF entity.

Certainly, alternatively, the PCF entity may not be a common network element in the first network and the second network. In this case, the PCF entity may obtain the network status of the second network in a manner of interacting with a common network element in the first network and the second network. This is not specifically limited in this embodiment of this application.

The PCF entity determines that the network status of the second network meets the preset condition.

If the network status includes a congestion status, that the network status of the second network meets the preset condition specifically means that the second network is not congested.

If the network status includes a quota, that the network status of the second network meets the preset condition specifically means that traffic that can be used by the user in a specified period or in a session meets a user requirement.

The PCF entity sends a PDU-CAN session establishment response (session establishment response) to the SMF entity. Correspondingly, the SMF entity receives the PDU-CAN session establishment response from the PCF entity. The PDU-CAN session establishment response includes the access network type corresponding to the second network. The access network type corresponding to the second network is used to instruct the terminal to redirect a session of the terminal to the second network.

The SMF entity sends the access network type corresponding to the second network to the terminal by using the AN device <NUM>. Correspondingly, the terminal receives the access network type corresponding to the second network from the SMF entity.

It should be noted that this embodiment of this application is described by using an example in which the terminal accesses the first network by using the AN device <NUM>, and accesses the second network by using the AN device <NUM>. Uniform descriptions are provided herein, and details are not described below again.

The terminal redirects the session of the terminal to the second network based on the access network type corresponding to the second network.

For a specific implementation in which the terminal redirects the session of the terminal to the second network, refer to an existing procedure in which the terminal establishes a session in the first network.

In the method for selecting an access network type provided in this embodiment of this application, a network side may select the access network type based on the network status of the network, and redirect the session of the terminal from the first network to the second network when the network status of the first network does not meet the preset condition. In other words, control by the network side over selection of the access network type by the terminal is enhanced, and the access network type is more flexibly selected by the terminal.

In addition, step S411 and step S412 are optional steps. In this embodiment of this application, step S413 may alternatively be directly performed after step S410. This is not specifically limited in this embodiment of this application. When step S413 is performed after step S411 and step S412, because the network status of the second network meets the preset condition, a problem in the prior art that a selected access network type is inappropriate because network access is selected based on a current location of a terminal can be avoided, so that subsequent communication efficiency can be improved.

Optionally, <FIG>, <FIG>, and <FIG> show a method for selecting an access network type according to an embodiment of this application. The following describes the method by using an example in which the method for selecting an access network type is applied to a PDU session modification procedure. For example, the method relates to interaction between a terminal, an AN device <NUM>, an AN device <NUM>, an AMF entity, a UPF entity <NUM>, a UPF entity <NUM>, an SMF entity, a PCF entity, and a UDM entity.

The PCF entity determines that a network status of a first network does not meet a preset condition, where the first network is a network currently accessed by the terminal.

For a related implementation of step S501, refer to step S407 shown in <FIG> and <FIG>.

The PCF entity sends a terminal location request to the AMF entity. Correspondingly, the AMF entity receives the terminal location request from the PCF entity.

The AMF entity sends terminal location information to the PCF entity. Correspondingly, the PCF entity receives the terminal location information from the AMF entity.

Optionally, the PCF entity may alternatively send a terminal location request to the SMF entity. Correspondingly, after receiving the terminal location request from the PCF entity, the SMF entity sends the terminal location information to the PCF entity. A network element from which the PCF entity obtains the terminal location information is not limited in this embodiment of this application.

S504 to S508 are the same as S408 to S412. For details, refer to the embodiment shown in <FIG> and <FIG>.

The PCF entity sends a PDU-CAN session modification request (session modification request) to the SMF entity. Correspondingly, the SMF entity receives the PDU-CAN session modification request from the PCF entity. The PDU-CAN session modification request includes an access network type corresponding to a second network. The access network type corresponding to the second network is used to instruct the terminal to redirect a session of the terminal to the second network.

The SMF entity sends a PDU-CAN session modification response (session modification response) to the PCF entity. Correspondingly, the SMF entity receives the PDU-CAN session modification response from the PCF entity.

The SMF entity sends the access network type corresponding to the second network to the terminal by using the AN device <NUM>. Correspondingly, the terminal receives the access network type corresponding to the second network from the SMF entity.

The terminal redirects the session of the terminal to the second network based on the access network type corresponding to the second network.

Optionally, a session and service continuity (session and service continuity, SSC) mode includes a first SSC mode, a second SSC mode, and a third SSC mode. In the first SSC mode, after the terminal moves, an anchor of a PDU session remains unchanged. Therefore, continuity of the internet protocol (internet protocol, IP) can be maintained. In the second SSC mode, after the terminal moves, the SMF entity releases an old session, then selects an appropriate anchor for the current location of the terminal, and establishes a new session by using the new anchor. In the third SSC mode, after the terminal moves, the SMF entity selects an appropriate anchor for the current location of the terminal, and establishes a new session by using the new anchor. A service on an old session is migrated to the new session, or an old session is released after a period of time. The anchor in this embodiment of this application specifically refers to a UPF entity. Uniform descriptions are provided herein, and details are not described below again.

For different SSC modes, as shown in <FIG>, <FIG>, and <FIG>, this embodiment of this application further includes the following steps.

If a current SSC mode is the first SSC mode, the method further includes the following step S513.

The SMF entity sends first indication information to the terminal. Correspondingly, the terminal receives the first indication information from the SMF entity. The first indication information is used to instruct the terminal to redirect the session to the second network after the session is deactivated.

In this way, the terminal performs step S512 after deactivating the session of the terminal in the first network.

If the current SSC mode is the second SSC mode, the method further includes the following steps S514 and S515.

The SMF entity sends second indication information to the terminal. Correspondingly, the terminal receives the second indication information from the SMF entity. The second indication information is used to instruct the terminal to release the session of the terminal in the first network.

The terminal releases the session of the terminal in the first network.

If the current SSC mode is the third SSC mode, the method further includes the following steps S516 and S517.

The SMF entity sends a timing length to the terminal. Correspondingly, the terminal receives the timing length from the SMF entity. The timing length is used to indicate a time for which the session of the terminal in the first network is released.

In this way, after step S512, the terminal performs step S517.

The terminal immediately releases the session of the terminal in the first network after redirecting the session of the terminal to the second network based on the timing length, or releases the session of the terminal in the first network after redirecting the session of the terminal to the second network for a period of time.

Optionally, the first indication information in step S513, the second indication information in step S514, or the timing length in step S516 and the access network type corresponding to the second network in step S511 may be carried in a message and sent to the terminal in one step, or may be carried in different messages and sent to the terminal in different steps. This is not specifically limited in this embodiment of this application.

It should be noted that the embodiment shown in <FIG>, <FIG>, and <FIG> is described by using an example in which the SMF entity performs a corresponding operation in an SSC mode of a current session. Optionally, in this embodiment of this application, the terminal may alternatively perform the foregoing operation in the SSC mode that is of the current session and that is received from the SMF entity. For example, if the current SSC mode is the first SSC mode, after receiving the SSC mode of the current session from the SMF entity, the terminal deactivates the session of the terminal in the first network and then performs step S512. If the current SSC mode is the second SSC mode, after receiving the SSC mode of the current session from the SMF entity, the terminal further performs step S515. If the current SSC mode is the third SSC mode, after receiving the SSC mode of the current session from the SMF entity, the terminal further performs step S517. This is not specifically limited in this embodiment of this application.

Optionally, <FIG> and <FIG> show a method for selecting an access network type according to an embodiment of this application. The following describes the method by using an example in which the method for selecting an access network type is applied to a packet data unit (packet data unit, PDU) session establishment procedure. For example, the method relates to interaction between a terminal, an AN device <NUM>, an AN device <NUM>, an AMF entity, a UPF entity <NUM>, a UPF entity <NUM>, an SMF entity, a PCF entity, and a UDM entity.

S601 to S605 are the same as S401 to S405. For details, refer to the embodiment shown in <FIG> and <FIG>.

The SMF entity sends a PDU-CAN session establishment request to the PCF entity. Correspondingly, the PCF entity receives the PDU-CAN session establishment request from the SMF entity. The PDU-CAN session establishment request includes the current access network type.

The PCF entity determines that the network status of the first network does not meet the preset condition, where the first network is a network currently accessed by the terminal, that is, a network corresponding to the current access network type.

For a related implementation of step S607, refer to step S407 shown in <FIG> and <FIG>.

The PCF entity obtains a network status of a second network, where the second network is a network other than the first network.

For a related implementation of step S608, refer to step S411 shown in <FIG> and <FIG>.

The PCF entity determines that the network status of the second network meets the preset condition.

For a related implementation of step S609, refer to step S412 shown in <FIG> and <FIG>.

The PCF entity sends a PDU-CAN session establishment response (session establishment response) to the SMF entity. Correspondingly, the SMF entity receives the PDU-CAN session establishment response from the PCF entity. The PDU-CAN session establishment response includes the access network type corresponding to the second network. The access network type corresponding to the second network is used to instruct the terminal to redirect a session of the terminal to the second network.

The SMF entity sends the access network type corresponding to the second network to the terminal by using the AN device <NUM>. Correspondingly, the terminal receives the access network type corresponding to the second network from the SMF entity.

The terminal detects, based on the access network type corresponding to the second network, whether the second network exists at a current location.

The terminal sends a first message to the SMF entity by using the AN device <NUM>. Correspondingly, the SMF entity receives the first message from the terminal. The first message is used to indicate whether the terminal has detected the second network.

If the SMF entity determines, based on the first message, that the terminal has detected the second network, the SMF entity sends a second message to the terminal. Correspondingly, the terminal receives the second message from the SMF entity. The second message is used to instruct the terminal to redirect the session of the terminal to the second network.

Optionally, if the SMF entity determines, based on the first message, that the terminal cannot detect the second network, the SMF entity continues to establish a session in the current first network. This is not specifically limited in this embodiment of this application.

Optionally, the SMF entity in steps S613 and S614 may alternatively be replaced with the PCF entity. To be specific, the terminal sends the first message to the PCF entity by using the AN device <NUM>. If the PCF entity determines, based on the first message, that the terminal has detected the second network, the PCF entity sends the second message to the terminal. If the PCF entity determines, based on the first message, that the terminal cannot detect the second network, the PCF entity continues to establish a session in the current first network. This is not specifically limited in this embodiment of this application.

The terminal redirects the session of the terminal to the second network based on the access network type corresponding to the second network.

Optionally, in this embodiment of this application, the terminal may directly redirect the session of the terminal to the second network based on the access network type corresponding to the second network after detecting that the second network exists at the current location. Certainly, if the terminal detects that the second network does not exist at the current location, the terminal needs to send indication information to the SMF entity or the PCF entity. The indication information is used to instruct to continue to establish a session in the current first network. This is not specifically limited in this embodiment of this application.

In addition, step S608 and step S609 are optional steps. In this embodiment of this application, step S610 may alternatively be directly performed after step S607. This is not specifically limited in this embodiment of this application. When step S610 is performed after step S608 and step S609, because the network status of the second network meets the preset condition, a problem in the prior art that a selected access network type is inappropriate because network access is selected based on a current location of a terminal can be avoided, so that subsequent communication efficiency can be improved.

Optionally, <FIG>, <FIG>, and <FIG> show a method for selecting an access network type according to an embodiment of this application. The following describes the method by using an example in which the method for selecting an access network type is applied to PDU session establishment completion. For example, the method relates to interaction between a terminal, an AN device <NUM>, an AN device <NUM>, an AMF entity, a UPF entity <NUM>, a UPF entity <NUM>, an SMF entity, a PCF entity, and a UDM entity.

The PCF entity determines that a network status of a first network does not meet a preset condition, where the first network is a network currently accessed by the terminal.

For a related implementation of step S701, refer to step S407 shown in <FIG> and <FIG>.

The PCF entity obtains a network status of a second network, where the second network is a network other than the first network.

For a related implementation of step S702, refer to step S411 shown in <FIG> and <FIG>.

The PCF entity determines that the network status of the second network meets the preset condition.

For a related implementation of step S703, refer to step S412 shown in <FIG> and <FIG>.

The PCF entity sends a PDU-CAN session modification request (session modification request) to the SMF entity. Correspondingly, the SMF entity receives the PDU-CAN session modification request from the PCF entity. The PDU-CAN session modification request includes an access network type corresponding to a second network. The access network type corresponding to the second network is used to instruct the terminal to redirect a session of the terminal to the second network.

The SMF entity sends a PDU-CAN session modification response (session modification response) to the PCF entity. Correspondingly, the SMF entity receives the PDU-CAN session modification response from the PCF entity.

The SMF entity sends the access network type corresponding to the second network to the terminal by using the AN device <NUM>. Correspondingly, the terminal receives the access network type corresponding to the second network from the SMF entity.

The terminal detects, based on the access network type corresponding to the second network, whether the second network exists at a current location.

The terminal sends a first message to the SMF entity by using the AN device <NUM>. Correspondingly, the SMF entity receives the first message from the terminal. The first message is used to indicate whether the terminal has detected the second network.

If the SMF entity determines, based on the first message, that the terminal has detected the second network, the SMF entity sends a second message to the terminal. Correspondingly, the terminal receives the second message from the SMF entity. The second message is used to instruct the terminal to redirect the session of the terminal to the second network.

The terminal redirects the session of the terminal to the second network based on the access network type corresponding to the second network.

Optionally, for different SSC modes, as shown in <FIG>, <FIG>, and <FIG>, this embodiment of this application further includes the following steps.

If a current SSC mode is the first SSC mode, the method further includes the following step S711.

The SMF entity sends first indication information to the terminal. Correspondingly, the terminal receives the first indication information from the SMF entity. The first indication information is used to instruct the terminal to redirect the session to the second network after the session is deactivated.

In this way, the terminal performs step S710 after deactivating the session of the terminal in the first network.

If the current SSC mode is the second SSC mode, the method further includes the following steps S712 and S713.

The SMF entity sends second indication information to the terminal. Correspondingly, the terminal receives the second indication information from the SMF entity. The second indication information is used to instruct the terminal to release the session of the terminal in the first network.

The terminal releases the session of the terminal in the first network.

If the current SSC mode is the third SSC mode, the method further includes the following steps S714 and S715.

The SMF entity sends a timing length to the terminal. Correspondingly, the terminal receives the timing length from the SMF entity. The timing length is used to indicate a time for which the session of the terminal in the first network is released.

In this way, after step S710, the terminal performs step S715.

The terminal immediately releases the session of the terminal in the first network after redirecting the session of the terminal to the second network based on the timing length, or releases the session of the terminal in the first network after redirecting the session of the terminal to the second network for a period of time.

Optionally, the first indication information in step S711, the second indication information in step S712, or the timing length in step S714 and the access network type corresponding to the second network in step S706 may be carried in a message and sent to the terminal in one step, or may be carried in different messages and sent to the terminal in different steps. This is not specifically limited in this embodiment of this application.

Optionally, the first indication information in step S711, the second indication information in step S712, or the timing length in step S714 may be carried in the second message in step S709 and sent to the terminal. This is not specifically limited in this embodiment of this application.

Optionally, the SMF entities in steps S708, S709, S711, S712, and S714 may alternatively be replaced with the PCF entities. This is not specifically limited in this embodiment of this application.

It should be noted that the embodiment shown in <FIG>, <FIG>, and <FIG> is described by using an example in which the SMF entity performs a corresponding operation in an SSC mode of a current session. Optionally, in this embodiment of this application, the terminal may alternatively perform the foregoing operation in the SSC mode that is of the current session and that is received from the SMF entity. For example, if the current SSC mode is the first SSC mode, after receiving the SSC mode of the current session from the SMF entity, the terminal deactivates the session of the terminal in the first network and then performs step S710. If the current SSC mode is the second SSC mode, after receiving the SSC mode of the current session from the SMF entity, the terminal further performs step S713. If the current SSC mode is the third SSC mode, after receiving the SSC mode of the current session from the SMF entity, the terminal further performs step S715. This is not specifically limited in this embodiment of this application.

In addition, step S702 and step S703 are optional steps. In this embodiment of this application, step S704 may alternatively be directly performed after step S701. This is not specifically limited in this embodiment of this application. When step S704 is performed after step S702 and step S703, because the network status of the second network meets the preset condition, a problem in the prior art that a selected access network type is inappropriate because network access is selected based on a current location of a terminal can be avoided, so that subsequent communication efficiency can be improved.

The foregoing mainly describes, from a perspective of interaction between network elements, the solutions provided in the embodiments of this application. It may be understood that to implement the foregoing functions, the PCF entity and the SMF entity include corresponding hardware structures and/or software modules for implementing the functions. A person skilled in the art should easily be aware that units and algorithm steps in the examples described with reference to the embodiments disclosed in this specification may be implemented in a form of hardware or in a form of a combination of hardware and computer software in this application. Whether a function is performed by hardware or hardware driven by computer software depends on particular applications and design constraints of the technical solutions. A person skilled in the art may use a different method for each particular application to implement the described functions, but it should not be considered that the implementation goes beyond the scope of this application.

In the embodiments of this application, functional module division may be performed for the PCF entity and the SMF entity based on the foregoing method examples. For example, functional modules may be divided based on functions, or two or more functions may be integrated into one processing module. The integrated module may be implemented in a form of hardware, or may be implemented in a form of a software functional module. It should be noted that, in the embodiments of this application, module division is an example, and is merely a logical function division. In actual implementation, another division manner may be used.

For example, when the functional modules are divided based on the functions, <FIG> is a possible schematic structural diagram of a PCF entity <NUM> in the foregoing embodiments. The PCF entity <NUM> includes a determining module <NUM> and a sending module <NUM>.

The determining module <NUM> is configured to determine that a network status of a first network does not meet a preset condition, where the first network is a network currently accessed by a terminal. The sending module <NUM> is configured to send an access network type corresponding to a second network to the terminal, where the access network type corresponding to the second network is used to instruct the terminal to redirect a session of the terminal to the second network, and the second network is a network other than the first network.

The network status in this embodiment of this application includes at least one of a congestion status or a quota.

Optionally, as shown in <FIG>, the PCF entity in this embodiment of this application further includes an obtaining module <NUM>.

The obtaining module <NUM> is configured to obtain a network status of the second network before the sending module <NUM> sends the access network type corresponding to the second network to the terminal. The determining module <NUM> is further configured to determine that the network status of the second network meets the preset condition.

Optionally, the obtaining module <NUM> is configured to obtain location information of the terminal. The determining module <NUM> is further configured to learn, based on the location information of the terminal, that the second network covers a current location of the terminal.

Optionally, the determining module <NUM> is specifically configured to: send a request message to a UDM entity, where the request message includes the location information of the terminal and is used to request access network type information for the current location of the terminal; receive a response message from the UDM entity, where the response message includes the access network type information for the current location of the terminal; and learn, based on the access network type information for the current location of the terminal, that the second network covers the current location of the terminal.

Optionally, the obtaining module <NUM> is specifically configured to: receive the location information of the terminal from an SMF entity; or the obtaining module <NUM> is specifically configured to: receive the location information of the terminal from an AMF entity.

Optionally, as shown in <FIG>, the PCF entity further includes a receiving module <NUM>.

The sending module <NUM> is further configured to send a request message to the terminal, where the request message is used to request access network type information for a current location of the terminal. The receiving module <NUM> is configured to receive a response message from the terminal, where the response message includes the access network type information for the current location of the terminal. The determining module <NUM> is further configured to learn, based on the access network type information for the current location of the terminal, that the second network covers the current location of the terminal.

Optionally, the receiving module <NUM> is configured to: receive a first message from the terminal after the sending module <NUM> sends the access network type corresponding to the second network to the terminal, where the first message is used to indicate whether the terminal has detected the second network.

The sending module is configured to send a second message to the terminal if the determining module <NUM> determines, based on the first message, that the terminal has detected the second network, where the second message is used to instruct the terminal to redirect the session of the terminal to the second network.

When the function modules are divided through integration, <FIG> is a possible schematic structural diagram of a PCF entity <NUM> in the foregoing embodiments. As shown in <FIG>, the PCF entity <NUM> includes a processing module <NUM> and a communications module <NUM>. The processing module <NUM> performs an action of the determining module <NUM> in <FIG>, and the communications module <NUM> performs an action of the sending module <NUM> in <FIG>. Optionally, the processing module <NUM> performs an action of the obtaining module <NUM> in <FIG>, and the communications module <NUM> performs an action of the receiving module <NUM> in <FIG>. For details, refer to the embodiment shown in <FIG>.

Alternatively, for example, when the functional modules are divided based on the functions, <FIG> is a possible schematic structural diagram of an SMF entity <NUM> in the foregoing embodiments. The SMF entity <NUM> includes a receiving module <NUM> and a sending module <NUM>.

The receiving module <NUM> is configured to receive an access network type corresponding to a second network from a PCF entity. The sending module <NUM> is configured to send an access network type corresponding to a second network to the terminal, where the access network type corresponding to the second network is used to instruct the terminal to redirect a session of the terminal to the second network.

Optionally, the second network is a network, other than a first network, in networks that cover a current location of the terminal, and the first network is a network currently accessed by the terminal.

Optionally, the second network is a network other than a first network, and the first network is a network currently accessed by the terminal.

Optionally, as shown in <FIG>, the SMF entity <NUM> further includes a determining module <NUM>. The receiving module <NUM> is configured to: receive a first message from the terminal after the sending module <NUM> sends the access network type corresponding to the second network to the terminal, where the first message is used to indicate whether the terminal has detected the second network. The sending module <NUM> is further configured to send a second message to the terminal if the determining module <NUM> determines, based on the first message, that the terminal has detected the second network, where the second message is used to instruct the terminal to redirect the session of the terminal to the second network.

Optionally, the sending module <NUM> is further configured to send first indication information to the terminal if a current SSC mode is a first SSC mode, where the first indication information is used to instruct the terminal to redirect the session to the second network after the session is deactivated.

Alternatively, the sending module <NUM> is further configured to send second indication information to the terminal if a current SSC mode is a second SSC mode, where the second indication information is used to instruct to release the session.

Alternatively, the sending module <NUM> is further configured to send a timing length to the terminal if a current SSC mode is a third SSC mode, where the timing length is used to indicate a time for which the session is released.

When the function modules are divided through integration, <FIG> is a possible schematic structural diagram of an SMF entity <NUM> in the foregoing embodiments. As shown in <FIG>, the SMF entity <NUM> includes a communications module <NUM>. The communications module <NUM> performs actions of the receiving module <NUM> and the sending module <NUM> in <FIG>. Optionally, as shown in <FIG>, the SMF entity <NUM> further includes a processing module <NUM>. The processing module <NUM> performs an action of the determining module <NUM> in <FIG>. For details, refer to the embodiment shown in <FIG>.

In this embodiment, the PCF entity and the SMF entity are presented in a form in which the functional modules are divided based on the functions, or the PCF entity and the SMF entity are presented in a form in which the functional modules are divided through integration. The "module" herein may be an application-specific integrated circuit (application-specific integrated circuit, ASIC), a circuit, a processor and a memory that execute one or more software or firmware programs, an integrated logic circuit, and/or another device that can provide the foregoing functions. In a simple embodiment, a person skilled in the art may figure out that the PCF entity and the SMF entity may be implemented by using the communications device in <FIG>.

<FIG> is a schematic diagram of a hardware structure of a communications device <NUM> according to an embodiment of this application. The communications device <NUM> includes a processor <NUM>, a communications bus <NUM>, and a communications interface <NUM>.

The processor <NUM> may be a general purpose processor, for example, a central processing unit (Central Processing Unit, CPU), a network processor (network processor, NP), or a combination of a CPU and an NP. Alternatively, the processor <NUM> may be a microprocessor (MCU), an ASIC, a programmable logic device (programmable logic device, PLD), or a combination thereof. The PLD may be a complex programmable logic device (complex programmable logic device, CPLD), a field-programmable gate array (field-programmable gate array, FPGA), a generic array logic (English: generic array logic, GAL for short), or any combination thereof.

The communications bus <NUM> may include a channel on which information is transmitted between the foregoing components.

The communications interface <NUM> may be any apparatus such as a transceiver, and is configured to communicate with another device or a communications network. The communications interface <NUM> may include an Ethernet interface, a radio access network (radio access network, RAN) interface, a wireless local area network (wireless local area networks, WLAN) interface, and the like.

Optionally, the communications device <NUM> may further include a memory <NUM>. The memory <NUM> may include a volatile memory (English: volatile memory), for example, a random access memory (English: randomaccess memory, RAM for short); or the memory may include a nonvolatile memory (English: non-volatile memory), for example, a flash memory (English: flash memory), a hard disk drive (English: hard disk drive, HDD for short), or a solid-state drive (English: solid-state drive, SSD for short); or the memory <NUM> may include a combination of the foregoing types of memories.

Optionally, the memory <NUM> is configured to store program code. The processor <NUM> is configured to execute program code stored in the memory <NUM>, to implement the method for selecting an access network type provided in this embodiment of this application.

During specific implementation, the processor <NUM> may include one or more CPUs, for example, a CPU <NUM> and a CPU <NUM> in <FIG>. The CPU may be a single-core CPU, or may be a multi-core CPU.

During specific implementation, in an embodiment, the communications device <NUM> may further include an output device <NUM> and an input device <NUM>. The output device <NUM> communicates with the processor <NUM>, and may display information in a plurality of manners. For example, the output device <NUM> may be a liquid crystal display (liquid crystal display, LCD), a light emitting diode (light emitting diode, LED) display device, a cathode ray tube (cathode ray tube, CRT) display device, or a projector (projector). The input device <NUM> communicates with the processor <NUM>, and may accept input of a user in a plurality of manners. For example, the input device <NUM> may be a mouse, a keyboard, a touchscreen device, or a sensing device.

The communications device <NUM> may be a general-purpose node or a dedicated node. During specific implementation, the communications device <NUM> may be a desktop computer, a portable computer, a network server, a palmtop computer (personal digital assistant, PDA), a mobile phone, a tablet computer, a wireless terminal device, an embedded device, or a device with a structure similar to that in <FIG>. A type of the communications device <NUM> is not limited in this embodiment of this application.

For example, the determining module <NUM>, the sending module <NUM>, the obtaining module <NUM>, and the receiving module <NUM> in <FIG> may be implemented by using the processor <NUM> and the memory <NUM> in <FIG>. Specifically, the determining module <NUM>, the sending module <NUM>, the obtaining module <NUM>, and the receiving module <NUM> may be executed by the processor <NUM> by invoking the application program code stored in the memory <NUM>. This is not limited in this embodiment of this application. Alternatively, for example, the processing module <NUM> and the communications module <NUM> in <FIG> may be implemented by the processor <NUM> and the memory <NUM> in <FIG>. Specifically, the processing module <NUM> and the communications module <NUM> may be executed by the processor <NUM> by invoking the application program code stored in the memory <NUM>. This is not limited in this embodiment of this application.

For example, the receiving module <NUM>, the sending module <NUM>, and the determining module <NUM> in <FIG> may be implemented by using the processor <NUM> and the memory <NUM> in <FIG>. Specifically, the receiving module <NUM>, the sending module <NUM>, and the determining module <NUM> may be executed by the processor <NUM> by invoking the application program code stored in the memory <NUM>. This is not limited in this embodiment of this application. Alternatively, for example, the processing module <NUM> and the communications module <NUM> in <FIG> may be implemented by the processor <NUM> and the memory <NUM> in <FIG>. Specifically, the processing module <NUM> and the communications module <NUM> may be executed by the processor <NUM> by invoking the application program code stored in the memory <NUM>. This is not limited in this embodiment of this application.

The PCF entity and the SMF entity provided in the embodiments of this application may be configured to perform the foregoing method for selecting an access network type. Therefore, for technical effects that can be achieved by the PCF entity and the SMF entity, refer to the foregoing method embodiments. Details are not described herein again in this embodiment of this application.

All or some of the foregoing embodiments may be implemented by means of software, hardware, firmware, or any combination thereof. When a software program is used to implement the embodiments, the embodiments may be implemented completely or partially in a 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 procedures or functions according to the embodiments of this application are all or partially generated. The computer may be a general-purpose computer, a dedicated computer, a computer network, or other programmable apparatuses. The computer instructions may be stored in a computer-readable storage medium or may be transmitted from a computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from a website, computer, server, or data center to another website, computer, server, or data center in a wired (for example, a coaxial cable, an optical fiber, or a digital subscriber line (digital subscriber line, DSL)) or wireless (for example, infrared, radio, and microwave) manner. The computer-readable storage medium may be any usable medium accessible by a computer, or a data storage device, such as a server or a data center, integrating one or more usable media. The usable medium may be a magnetic medium (for example, a floppy disk, a hard disk, or a magnetic tape), an optical medium (for example, a DVD), a semiconductor medium (for example, a solid-state drive (solid state disk, SSD)), or the like.

Although this application is described with reference to the embodiments, in a process of implementing this application that claims protection, a person skilled in the art may understand and implement another variation of the disclosed embodiments by viewing the accompanying drawings, disclosed content, and the appended claims. In the claims, "comprising" (comprising) does not exclude another component or another step, and "a" or "one" does not exclude a case of "a plurality of". A single processor or another unit may implement several functions listed in the claims. Some measures are set forth in dependent claims that are different from each other, but this does not mean that these measures cannot be combined to produce a good effect.

Claim 1:
A method for selecting an access network type, wherein the method comprises:
determining (S301), by a policy control function entity, that a quota of a first network does not meet a preset condition, wherein the first network is a network currently accessed by a terminal, wherein the quota of the first network refers to traffic that can be used by a user in a specified period in the first network, wherein that the quota of the first network does not meet the preset condition specifically means that traffic that can be used by the user in a specified period does not meet a user requirement; and
sending (S302, S303), by the policy control function entity, an access network type corresponding to a second network to the terminal, wherein the access network type corresponding to the second network is used to instruct the terminal to redirect a session of the terminal to the second network, and the second network is a network other than the first network,
wherein the method further comprises:
obtaining, by the policy control function entity, location information of the terminal; and
learning, by the policy control function entity based on the location information of the terminal, that the second network covers a current location of the terminal.