CN110710265B

CN110710265B - Network returning method and device and computer storage medium

Info

Publication number: CN110710265B
Application number: CN201880037293.7A
Authority: CN
Inventors: 刘建华; 杨宁
Original assignee: Guangdong Oppo Mobile Telecommunications Corp Ltd
Current assignee: Guangdong Oppo Mobile Telecommunications Corp Ltd
Priority date: 2018-02-05
Filing date: 2018-02-14
Publication date: 2021-03-05
Anticipated expiration: 2038-02-14
Also published as: CN110710247A; CN110710265A; WO2019148552A1; CN110710247B; WO2019148654A1

Abstract

The invention discloses a network returning method and a device and a computer storage medium, wherein the method comprises the following steps: the method comprises the steps that a terminal is switched or redirected from a first network to a second network, voice service is carried out under the second network, wherein in the process that the terminal is switched or redirected from the first network to the second network, the reason value of the switching or redirection is determined to be voice fallback, the reason value is used for indicating that the switching or redirection is caused by the voice fallback, and voice fallback indication information and/or a last used PLMN ID are sent to the second network; and after the terminal completes the voice service in the second network, receiving a switching or redirection message sent by the second network, and switching or redirecting from the second network to the first network based on the switching or redirection message.

Description

Network returning method and device and computer storage medium

Technical Field

The present invention relates to the field of wireless communications technologies, and in particular, to a network return method and apparatus, and a computer storage medium.

Background

Fifth generation (5G, 5)^thGeneration) Mobile communication System, also known as New Radio (NR) System, at the early stages of 5G network deployment or in the case of 5G network congestion, the 5G network may not be able to support Voice over NR (VoNR) and the 5G network needs to trigger from the 5G network to the fourth Generation (4G, 4G)^thGeneration) network, and completing Voice service of the terminal through Voice over Long Term Evolution (VoLTE) of the 4G network.

At present, after the terminal completes the VoLTE voice service, there is no mechanism for the terminal to perform a 5G to 4G fallback specifically for establishing the voice service to trigger the terminal to perform a fast return to the 5G network, which affects the use experience of the terminal in the 5G network.

Disclosure of Invention

In order to solve the above technical problem, embodiments of the present invention provide a network returning method and apparatus, and a computer storage medium.

The network returning method provided by the embodiment of the invention comprises the following steps:

a terminal switches or redirects from a first Network to a second Network, and performs voice service in the second Network, wherein in the process of switching or redirecting from the first Network to the second Network, the terminal determines that a cause value of the switching or redirecting is voice fallback, the cause value is used to indicate that the switching or redirecting is caused by the voice fallback, and sends voice fallback indication information and/or a Last used Public Land Mobile Network IDentity (Last used PLMN ID) to the second Network;

and after the terminal completes the voice service in the second network, receiving a switching or redirection message sent by the second network, and switching or redirecting from the second network to the first network based on the switching or redirection message.

In this embodiment of the present invention, when the terminal is switched from the first network to the second network:

the terminal determines that the reason value of the handover is voice fallback, and the reason value is used for indicating that the handover is caused by the voice fallback, and the method includes the following steps:

the terminal receives a switching command sent by the first network, wherein the switching command carries voice fallback indication information;

the terminal determines that the reason value of the switching is voice fallback based on the switching command, and the reason value is used for indicating that the switching is caused by the voice fallback.

In this embodiment of the present invention, the switching, by the terminal, from the first network to the second network includes:

the terminal is switched from the first access network to the second access network and maintains the connection with the first core network.

the terminal is handed over from the first access network to the second access network and from the first core network to the second core network.

In this embodiment of the present invention, when the terminal is redirected from the first network to the second network:

the terminal determines that a reason value of the redirection is voice fallback, and the reason value is used for indicating that the redirection is caused by the voice fallback, and the method includes:

the terminal receives a redirection message sent by the first network, wherein the redirection message carries voice fallback indication information;

the terminal determines that a reason value of the redirection is voice fallback based on the redirection message, and the reason value is used for indicating that the redirection is caused by the voice fallback.

In this embodiment of the present invention, the redirection message is an N2 request message or a Radio Resource Control (RRC) connection release message.

The terminal determines that a cause value of the redirection is voice fallback based on the RRC connection release message, and the cause value is used for indicating that the redirection is caused by the voice fallback.

In this embodiment of the present invention, the determining, by the terminal, that the cause value of the handover or redirection is voice fallback, where the cause value is used to indicate that the handover or redirection is caused by the voice fallback, and includes:

after the terminal sends a Session Initiation Protocol (SIP) invite message, if a handover command or an RRC connection release message sent by the first network is received within a first time period, it is determined that a cause value of the handover or redirection is a voice fallback, where the cause value is used to indicate that the handover or redirection is caused by the voice fallback.

In this embodiment of the present invention, the sending, by the terminal, the voice fallback indication information and/or the last used PLMN ID to the second network includes:

and the terminal sends an Access Stratum (AS) parameter in an AS message and/or a Non-Access Stratum (NAS) message to the second network, wherein the AS parameter in the AS message and/or the NAS message carries the voice fallback indication information and/or the PLMN ID used last.

In this embodiment of the present invention, the AS message includes at least one of the following: RRC connection request message, handover complete message, RRC connection setup complete message.

In this embodiment of the present invention, the AS parameter in the NAS message includes at least one of: the AS parameter in the attach request message and the AS parameter in the tracking area update request message.

In this embodiment of the present invention, the access network element of the second network obtains the voice fallback indication information and/or the last used PLMN ID from the AS parameter in the AS message and/or the NAS message.

and the terminal sends an NAS message to the second network, wherein the NAS message carries the voice fallback indication information and/or the PLMN ID used last.

In this embodiment of the present invention, the NAS message includes at least one of: NAS message in attach request message, NAS message in tracking area update request message.

In this embodiment of the present invention, the core network element of the second network obtains the voice fallback indication information and/or the last used PLMN ID from the NAS message, and sends the voice fallback indication information and/or the last used PLMN ID to the access network element of the second network.

In this embodiment of the present invention, the sending, by the core network element of the second network, the voice fallback indication information and/or the last used PLMN ID to the access network element of the second network includes:

the core network element of the second network sends the voice fallback indication information and/or the last used PLMN ID to an access network element of the second network through a bearer establishment or release message; alternatively, the first and second electrodes may be,

and the core network element of the second network sends the voice fallback indication information and/or the last used PLMN ID to the access network element of the second network through the initial context establishment request message.

In this embodiment of the present invention, the core network element of the second network receives the voice fallback indication information and/or the last used PLMN ID sent by the core network element of the first network, and the core network element of the second network sends the voice fallback indication information and/or the last used PLMN ID to the access network element of the second network.

In the embodiment of the present invention, a core network element of a first network sends a request message for establishing a voice QoS flow to an access network element of the first network, and receives a rejection message sent by the access network element of the first network, where the rejection message carries a cause value, and the cause value is used to indicate that the rejection message is caused by the voice fallback; if the core network element of the first network receives the handover request message sent by the access network element of the first network within a first time period, the core network element of the first network determines that the reason for the handover request message is caused by the voice fallback.

In the embodiment of the present invention, after the terminal completes the voice service in the second network, the access network element of the second network completes bearer release, and the terminal receives a handover or redirection message sent by the second network.

In the embodiment of the present invention, after the terminal completes the voice service in the second network, the core network element of the second network completes bearer release, and the terminal receives a handover or redirection message sent by the core network element of the second network.

In the embodiment of the present invention, after the second network sends a handover or redirection message, the first network is selected as the target network of the terminal.

In the embodiment of the present invention, the method further includes: determining cell information and/or frequency information of the target network.

In the embodiment of the present invention, the first network is selected as the target network of the terminal based on the last used PLMN ID.

In the embodiment of the present invention, after the terminal completes the voice service in the second network and completes bearer release, the terminal receives an RRC release message sent by an access network element of the second network, releases an RRC connection to enter an idle state, performs cell reselection through a radio resource management RFSP policy, and returns to the first network.

In the embodiment of the present invention, after the terminal completes the voice service in the second network and completes bearer release, the terminal receives an RRC release message sent by a core network element of the second network, releases an RRC connection to enter an idle state, performs cell reselection through a radio resource management RFSP policy, and returns to the first network.

in the process that the terminal is switched or redirected from a first network to a second network, the second network receives voice fallback indication information and/or a last used PLMN ID sent by the terminal;

after the terminal completes the voice service in the second network, the second network sends a switching or redirection message to the terminal based on the voice fallback indication information and/or the last used PLMN ID, so as to trigger the terminal to switch from the second network or redirect to the first network.

In this embodiment of the present invention, the receiving, by the second network, the voice fallback indication information and/or the last used PLMN ID sent by the terminal includes:

the second network receives an AS parameter in an AS message and/or an NAS message sent by the terminal, wherein the AS parameter in the AS message and/or the NAS message carries voice fallback indication information and/or a PLMN ID used last;

and the access network element of the second network acquires the voice fallback indication information and/or the last used PLMN ID from the AS parameters in the AS message and/or the NAS message.

the second network receives an NAS message sent by the terminal, wherein the NAS message carries voice fallback indication information and/or a last used PLMN ID;

and the core network element of the second network acquires the voice fallback indicating information and/or the last used PLMN ID from the NAS message, and sends the voice fallback indicating information and/or the last used PLMN ID to an access network element of the second network.

In the embodiment of the present invention, after the terminal completes the voice service in the second network, the access network element of the second network completes bearer release, and sends a handover or redirection message to the terminal.

In the embodiment of the present invention, after the terminal completes the voice service in the second network, the core network element of the second network completes bearer release, and sends a handover or redirection message to the terminal.

In the embodiment of the present invention, after the terminal completes the voice service in the second network and completes bearer release, the access network element of the second network sends an RRC release message to the terminal, so that the terminal releases the RRC connection to enter an idle state, performs cell reselection through an RFSP policy, and returns to the first network.

In the embodiment of the present invention, after the terminal completes the voice service in the second network and completes bearer release, the core network element of the second network sends an RRC release message to the terminal, so that the terminal releases an RRC connection to enter an idle state, performs cell reselection through an RFSP policy, and returns to the first network.

The network returning device provided by the embodiment of the invention is applied to a terminal, and the device comprises:

a first network changing unit, configured to switch or redirect from a first network to a second network, and perform a voice service in the second network;

a determining unit, configured to determine, in a process of switching or redirecting the terminal from the first network to the second network, that a cause value of the switching or redirecting is voice fallback, where the cause value is used to indicate that the switching or redirecting is caused by the voice fallback;

a first sending unit, configured to send, by the second network, voice fallback indication information and/or a last used PLMN ID;

a first receiving unit, configured to receive a handover or redirection message sent by the second network after completing a voice service in the second network;

a second network changing unit, configured to switch or redirect from the second network to the first network based on the handover or redirection message.

the device further comprises: a second receiving unit, configured to receive a handover command sent by the first network, where the handover command carries voice fallback indication information;

the determining unit is configured to determine, based on the handover command, that a cause value of the handover is a voice fallback, where the cause value is used to indicate that the handover is caused by the voice fallback.

In this embodiment of the present invention, the first network changing unit is configured to switch from the first access network to the second access network and maintain the connection with the first core network unchanged.

In this embodiment of the present invention, the first network changing unit switches from the first access network to the second access network and switches from the first core network to the second core network.

the device further comprises: a third receiving unit, configured to receive a redirection message sent by the first network, where the redirection message carries voice fallback indication information;

the determining unit is configured to determine, based on the redirection message, that a cause value of the redirection is a voice fallback, where the cause value is used to indicate that the redirection is caused by the voice fallback.

In this embodiment of the present invention, the redirection message is an N2 request message or an RRC connection release message.

In the embodiment of the present invention, the apparatus further includes: a second sending unit, configured to send an SIP invite message;

the determining unit is configured to determine that a cause value of the handover or redirection is voice fallback if a handover command or an RRC connection release message sent by the first network is received within a first time period after the SIP invite message is sent, where the cause value is used to indicate that the handover or redirection is caused by the voice fallback.

In this embodiment of the present invention, the first sending unit is configured to send an AS parameter in an AS message and/or an NAS message to the second network, where the AS parameter in the AS message and/or the NAS message carries the voice fallback indication information and/or the last used PLMN ID.

In this embodiment of the present invention, the first sending unit is configured to send an NAS message to the second network, where the NAS message carries the voice fallback indication information and/or the last used PLMN ID.

In this embodiment of the present invention, after the terminal completes the voice service in the second network, the access network element of the second network completes bearer release, and the first receiving unit receives a handover or redirection message sent by the access network element of the second network.

In this embodiment of the present invention, after the terminal completes the voice service in the second network, the core network element of the second network completes bearer release, and the first receiving unit receives a handover or redirection message sent by the core network element of the second network.

In the embodiment of the present invention, after the first network is selected as the target network of the terminal, cell information and/or frequency information of the target network is determined.

In this embodiment of the present invention, after the terminal completes a voice service in the second network and completes bearer release, the first receiving unit receives an RRC release message sent by an access network element of the second network, releases an RRC connection to enter an idle state, performs cell reselection through an RFSP policy for radio resource management, and returns the cell reselection to the first network.

In this embodiment of the present invention, after the terminal completes a voice service in the second network and completes bearer release, the first receiving unit receives an RRC release message sent by a core network element of the second network, releases an RRC connection to enter an idle state, performs cell reselection through an RFSP policy for radio resource management, and returns the cell reselection to the first network.

The network returning device provided by the embodiment of the invention is applied to a network, and the device comprises:

a receiving unit, configured to receive, during a process of switching or redirecting a terminal from a first network to a second network, voice fallback indication information and/or a last used PLMN ID sent by the terminal;

a sending unit, configured to send a handover or redirection message to the terminal based on the voice fallback indication information and/or a last used PLMN ID after the terminal completes a voice service in the second network, so as to trigger the terminal to handover from the second network or redirect to the first network.

In the embodiment of the present invention, the receiving unit is configured to receive an AS parameter in an AS message and/or an NAS message sent by the terminal, where the AS parameter in the AS message and/or the NAS message carries voice fallback indication information and/or a last used PLMN ID; and acquiring the voice fallback indication information and/or the last used PLMN ID from the AS parameters in the AS message and/or the NAS message.

In the embodiment of the present invention, the receiving unit is configured to receive an NAS message sent by the terminal, where the NAS message carries the voice fallback indication information and/or the last used PLMN ID; and acquiring the voice fallback indication information and/or the last used PLMN ID from the NAS message, and sending the voice fallback indication information and/or the last used PLMN ID to an access network element of the second network.

In the embodiment of the present invention, the apparatus further includes:

a selecting unit, configured to select the first network as a target network of the terminal.

In the embodiment of the present invention, the apparatus further includes: a determining unit, configured to determine cell information and/or frequency information of the target network.

In this embodiment of the present invention, the selecting unit is configured to select the first network as a target network of the terminal based on the last used PLMN ID.

The computer storage medium provided by the embodiment of the invention stores computer executable instructions thereon, and the computer executable instructions realize the network returning method when being executed by a processor.

In the technical scheme of the embodiment of the invention, a terminal is switched or redirected from a first network to a second network, and voice service is carried out in the second network, wherein in the process of switching or redirecting the terminal from the first network to the second network, the reason value of the switching or redirection is determined to be voice fallback, the reason value is used for indicating that the switching or redirection is caused by the voice fallback, and voice fallback indication information and/or a last used PLMN ID are sent to the second network; and after the terminal completes the voice service in the second network, receiving a switching or redirection message sent by the second network, and switching or redirecting from the second network to the first network based on the switching or redirection message. By adopting the technical scheme of the embodiment of the invention, a judging and triggering mechanism is provided to realize that the terminal can quickly return to the 5G network after the voice of the terminal is finished on the 4G network, and the use experience of the terminal on the 5G network is ensured.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention. In the drawings:

FIG. 1 is a system architecture diagram of a 5G network according to an embodiment of the present invention;

FIG. 2 is a system architecture diagram of a 4G network according to an embodiment of the present invention;

fig. 3 is a schematic diagram of a Handover (HO) procedure according to an embodiment of the present invention;

fig. 4(a) is a first flowchart illustrating a network fallback according to an embodiment of the present invention;

fig. 4(b) is a second flowchart of a network fallback according to the embodiment of the present invention;

fig. 5 is a first flowchart of a network returning method according to an embodiment of the present invention;

fig. 6 is a second flowchart illustrating a network returning method according to an embodiment of the present invention;

fig. 7 is a first schematic structural diagram of a network returning apparatus according to an embodiment of the present invention;

fig. 8 is a schematic structural diagram of a network returning apparatus according to an embodiment of the present invention;

fig. 9 is a schematic structural diagram of a computer device according to an embodiment of the present invention.

Detailed Description

So that the manner in which the features and aspects of the embodiments of the present invention can be understood in detail, a more particular description of the embodiments of the invention, briefly summarized above, may be had by reference to the embodiments, some of which are illustrated in the appended drawings.

Fig. 1 is a system architecture diagram of a 5G network according to an embodiment of the present invention, and as shown in fig. 1, devices involved in the 5G network system include:

a terminal (UE), a Radio Access Network (RAN), a User Plane Function (UPF), a Data Network (DN), a Core Access and Mobility Management (AMF), a Session Management Function (SMF), a Policy Control Function (PCF), an Application Function (AF), an Authentication Server Function (AUSF), and a Unified Data Management (UDM).

Fig. 2 is a system architecture diagram of a 4G network according to an embodiment of the present invention, and as shown in fig. 2, devices involved in the 4G network system include:

a terminal (UE), an Evolved Universal Terrestrial Radio Access Network (E-UTRAN), a Mobility Management Entity (MME), a Serving GPRS Support Node (SGSN), a Home Subscriber Server (HSS), a Serving Gateway (Serving Gateway), a Packet Data Gateway (PDN Gateway), a Policy and Charging Rules Function (PCRF), a Policy and Charging Rules Function (Policy and Charging Rules Function).

The example of fig. 1 and fig. 2 is only one example of a network architecture for implementing the embodiment of the present invention, and the embodiment of the present invention is not limited to the network structure described in fig. 1 and fig. 2.

In the 5G network, the terminal needs to register to the 5G network to perform the related 5G service. The registration process of the 5G network is different from the attach process of the 4G network, the registration process in the 5G network does not include the session establishment process, that is, the session establishment process may not be executed when the terminal registers, the AMF sends the N11_ Request message with the session related information (such as Non-independent Networking (NSA) information) through an N11 interface to the SMF, and the SMF determines whether to trigger the session establishment process. Fig. 3 is a schematic diagram of a Handover (HO) procedure according to an embodiment of the present invention, and the example of fig. 3 describes a process of Handover from a 5G network to a 4G network.

At the initial stage of 5G network deployment or under the condition of 5G network congestion, the 5G network may not support VoNR, and the 5G network needs to trigger a Handover procedure or a Redirection procedure of 5G → 4G (as shown in fig. 4(a) and 4 (b)), so as to enable the 4G network to execute VoLTE, thereby completing the request of the UE for voice establishment. For the 5G- > 4G Handover process or the Redirection process, the following three processes are included:

1) radio Access Handover (RAT Handover, Radio Access Technologies Handover)

Namely: the 5G core network is not changed, when UE needs to execute voice, RAT fall back is triggered, RAT access is changed from NR to LTE, and then VoLTE operation is executed.

2) Evolved Packet System switching (EPS Handover, Evolved Packet System Handover)

Namely: the 5G core network is handed over to the 4G core network while the RAT will also change from NR to LTE and then VoLTE operation is performed.

3) RRC Redirection (RRC Redirection)

The base station of the 5G network directly sends an RRC Connection Release message to the UE, and carries Cell information (Cell ID) and Frequency (Frequency Band) information of a target network (e.g., 4G network).

1), 2), 3) above are all triggered by the RAN on the 5G network side (i.e. NG-RAN).

During the fall back from the 5G network to the 4G network, the following three situations occur:

1) the 5G core network (5GC) is unchanged and the RAT does not change its AMF during the fall back.

In this case, the NG-RAN sends a reject indication to the AMF in step 5b shown in fig. 4(a), indicating that the reject is due to an ongoing HO. It is the responsibility of the AMF to trigger the establishment of a QCI ═ 1bearer immediately after the HO is completed.

2)5GC is unchanged, and the AMF of the RAT is changed during the fall back process.

In this case, the NG-RAN sends a reject indication to the AMF in step 5b shown in fig. 4(a), indicating that the reject is due to an ongoing HO. When AMF changes, AMF sends reject indication to SMF indicating that the 5QI ═ 1 flow just sent by SMF was not successfully established because HO was ongoing. The SMF is responsible for triggering the establishment of the QCI ═ 1bearer immediately after the HO is completed.

3)5GC → 4G core network (EPC) Fallback, and RAT is also handed over by NR → LTE (i.e., EPS Fallback).

In this case, during the inter-system handover, the SMF is a combined module of the SMF and the PGW-C (generally referred to as SMF + PGW-C), and the combined module is responsible for triggering QCI ═ 1bearer establishment immediately after the inter-system handover is completed.

The technical scheme of the embodiment of the invention provides a judging and triggering mechanism to realize that a terminal can quickly return to a 5G network after finishing voice on the 4G network, in the 5G network, a registration flow and a session establishment flow are the most basic and important flows of Mobile Management (MM) and Session Management (SM), the embodiment of the invention adds a voice support identification to UE in the registration flow, reports the voice support identification to the network, sends the voice support identification to SMF through NAS-SM information, adds the voice support identification to UDM, sends the voice support identification to SMF through a Subscription data response (Subscription data response) information in the session establishment flow, and judges when the SMF falls back to the 4G by the 5G.

Fig. 5 is a first schematic flowchart of a network returning method according to an embodiment of the present invention, and as shown in fig. 5, the network returning method includes the following steps:

step 501: the method comprises the steps that a terminal is switched or redirected from a first network to a second network, voice service is carried out under the second network, wherein in the process that the terminal is switched or redirected from the first network to the second network, the reason value of the switching or redirection is determined to be voice fallback, the reason value is used for indicating that the switching or redirection is caused by the voice fallback, and voice fallback indication information and/or a last used PLMN ID are sent to the second network.

In one embodiment, the first network is a 5G network and the second network is a 4G network.

In the embodiment of the invention, how the terminal knows the executed switching or redirection is based on the voice fallback triggering is realized by the following modes:

the first method is as follows: in the case where the terminal is handed over from the first network to the second network: the terminal receives a switching command sent by the first network, wherein the switching command carries voice fallback indication information; the terminal determines that the reason value of the switching is voice fallback based on the switching command, and the reason value is used for indicating that the switching is caused by the voice fallback.

Here, the UE adds a "voice fallback" indication to the Handover Command message on the 5G network, and the indication lets the UE know that the triggered Handover is caused by voice fallback.

In the embodiment of the present invention, the terminal is switched from the first network to the second network, and has the following two switching manners:

1) RAT handover, namely: the terminal is switched from the first access network to the second access network and maintains the connection with the first core network.

2) EPS handover, namely: the terminal is handed over from the first access network to the second access network and from the first core network to the second core network.

The second method comprises the following steps: in case the terminal is redirected from the first network to the second network: the terminal receives a redirection message sent by the first network, wherein the redirection message carries voice fallback indication information; the terminal determines that a reason value of the redirection is voice fallback based on the redirection message, and the reason value is used for indicating that the redirection is caused by the voice fallback.

In an embodiment, the redirection message is an N2 request message or an RRC connection release message.

For example, the UE adds a "voice fallback" indication in the RRC Connection Release message on the 5G network, which lets the UE know that the triggered redirection is due to voice fallback.

The third method comprises the following steps: after the terminal sends the SIP invitation message, if a switching command or an RRC connection release message sent by the first network is received within a first time period, determining that the reason value for switching or redirection is voice fallback, wherein the reason value is used for indicating that the switching or redirection is caused by the voice fallback.

Here, after the UE sends the SIP Invite message, if the network side triggers a Handover or RRC Connection Release message within a specific time (a timer may be introduced), the UE considers that the Handover or redirection is caused by a voice fallback.

In the embodiment of the present invention, how the second network knows that the UE is a "voice fallback" UE is implemented by the following manner:

the first method is as follows: and the terminal sends the AS message and/or the AS parameter in the NAS message to the second network, wherein the AS parameter in the AS message and/or the AS parameter in the NAS message carries the voice fallback indication information and/or the PLMN ID used last.

In one embodiment, the AS message includes at least one of: RRC connection request message, handover complete message, RRC connection setup complete message.

In an embodiment, the AS parameter in the NAS message includes at least one of: the AS parameter in the attach request message and the AS parameter in the tracking area update request message.

Based on this, the access network element of the second network obtains the voice fallback indication information and/or the last used PLMN ID from the AS parameter in the AS message and/or the NAS message.

For example, the UE carries the voice fallback indication information and/or the last used PLMN ID in the AS parameter in the AS message and/or the NAS message of the 4G network, and identifies that the connection establishment with the 4G network is caused by voice fallback, and the AS message is implemented, for example: RRC Connection request (RRC Connection request), Handover complete (Handover complete), RRC Connection setup complete (RRC Connection setup complete); the AS parameters in the NAS message are implemented, for example: AS parameters in an Attach Request (Attach Request), AS parameters in a tracking area update Request (TAU Request), and the 4G base station (eNodeB) knows that the UE is a "voice fallback" UE and knows a last used PLMN ID through the AS parameters in the AS message and/or the NAS message.

The second method comprises the following steps: and the terminal sends an NAS message to the second network, wherein the NAS message carries the voice fallback indication information and/or the PLMN ID used last.

In one embodiment, the NAS message includes at least one of: NAS message in attach request message, NAS message in tracking area update request message.

Based on this, the core network element of the second network acquires the voice fallback indication information and/or the last used PLMN ID from the NAS message, and sends the voice fallback indication information and/or the last used PLMN ID to the access network element of the second network.

Here, the core network element of the second network sends the voice fallback indication information and/or the last used PLMN ID to the access network element of the second network through a bearer setup or release message; or, the core network element of the second network sends the voice fallback indication information and/or the last used PLMN ID to the access network element of the second network through the initial context setup request message.

Here, the UE carries the voice fallback indication information and/or the last used PLMN ID in the NAS message of the 4G network, and identifies that the connection establishment with the 4G network is caused by voice fallback, and the NAS message is implemented, for example: and adding voice fallback indication information and/or a last used PLMN ID in an NAS message of the Attach Request message, and carrying the voice fallback indication information and/or the last used PLMN ID in an NAS message of the TAU Request message.

The MME of the 4G network, upon receiving the indication, passes the indication to the eNodeB over the S1 interface in a subsequent message. For example: 1) voice fallback indication information and/or a last used PLMN ID may be carried in a QCI ═ 1Bearer Setup or release message to the eNodeB, and 2) voice fallback indication information and/or a last used PLMN ID may also be carried in an "Initial Context Setup Request" message to the eNodeB.

The third method comprises the following steps: and the core network element of the second network receives the voice fallback indication information and/or the last used PLMN ID sent by the core network element of the first network, and sends the voice fallback indication information and/or the last used PLMN ID to the access network element of the second network.

Here, the core network element of the second network is an MME, the core network element of the first network is an AMF, and the access network element of the second network is an eNodeB, for example: the AMF informs the MME of the voice fallback indication information and/or the last used PLMN ID over an N26 interface (interface between AMF and MME), after which the MME of the 4G network receives the indication and passes it to the eNodeB over an S1 interface in a subsequent message. For example: 1) voice fallback indication information and/or a last used PLMN ID may be carried in a QCI ═ 1Bearer Setup or release message to the eNodeB, and 2) voice fallback indication information and/or a last used PLMN ID may also be carried in an "InitialContext Setup Request" message to the eNodeB.

Here, the core network element of the first network is an AMF, and the access network element of the first network is a gnnodeb.

Step 502: and after the terminal completes the voice service in the second network, receiving a switching or redirection message sent by the second network, and switching or redirecting from the second network to the first network based on the switching or redirection message.

In the embodiment of the invention, how to trigger the network side to quickly return to the 5G network after the UE voice service is completed is realized by the following modes:

the first method is as follows: 1) after the terminal completes the voice service in the second network, the access network element of the second network completes the bearer release, and the terminal receives the switching or redirection message sent by the second network. Or, 2) after the terminal completes the voice service in the second network, the core network element of the second network completes bearer release, and the terminal receives a handover or redirection message sent by the core network element of the second network.

Optionally, after the second network sends a handover or redirection message, the first network is selected as the target network of the terminal.

Further, cell information and/or frequency information of the target network is determined.

Optionally, the first network is selected as a target network of the terminal based on the last used PLMN ID.

For example: after the UE finishes the call, the eNodeB or the MME finishes the QCI (1-specific load) Release, and then sends a Handover or RRC Release message to the UE, selects a target side access network, determines the Cell ID and the Frequency Band of the target network (5G), and the selection of the target side network can be realized according to the Last used PLMN ID.

The second method comprises the following steps: 1) and after the terminal completes the voice service in the second network and the bearer release, the terminal receives an RRC release message sent by an access network element of the second network, releases the RRC connection to enter an idle state, performs cell reselection through a radio resource management (RFSP) strategy, and returns to the first network. Or, 2) after the terminal completes the voice service in the second network and completes bearer release, the terminal receives an RRC release message sent by a core network element of the second network, releases an RRC connection to enter an idle state, performs cell reselection through a radio resource management RFSP policy, and returns to the first network.

For example: after the UE finishes the call and finishes the QCI (quaternary ammonium chloride) < 1 > dedicated load Release, the eNodeB or the MME sends an RRC Connection Release message to the UE to trigger the UE to Release RRC Connection, so that the UE quickly returns to an Idle (Idle) state, and the UE performs cell reselection to return to the 5G network through a radio resource management (RFSP) strategy.

Fig. 6 is a schematic flowchart of a second network returning method according to an embodiment of the present invention, and as shown in fig. 6, the network returning method includes the following steps:

step 601: in the process of switching or redirecting the terminal from the first network to the second network, the second network receives the voice fallback indication information and/or the last used PLMN ID sent by the terminal.

In the embodiment of the present invention, the second network receives the voice fallback indication information and/or the last used PLMN ID sent by the terminal, and the method is implemented as follows:

the first method is as follows: the second network receives an AS parameter in an AS message and/or an NAS message sent by the terminal, wherein the AS parameter in the AS message and/or the NAS message carries voice fallback indication information and/or a PLMN ID used last; and the access network element of the second network acquires the voice fallback indication information and/or the last used PLMN ID from the AS parameters in the AS message and/or the NAS message.

In an embodiment, the access network element of the second network obtains the voice fallback indication information and/or the last used PLMN ID from the AS parameter in the AS message and/or the NAS message.

The second method comprises the following steps: the second network receives an NAS message sent by the terminal, wherein the NAS message carries voice fallback indication information and/or a last used PLMN ID; and the core network element of the second network acquires the voice fallback indicating information and/or the last used PLMN ID from the NAS message, and sends the voice fallback indicating information and/or the last used PLMN ID to an access network element of the second network.

In an embodiment, the core network element of the second network obtains the voice fallback indication information and/or the last used PLMN ID from the NAS message, and sends the voice fallback indication information and/or the last used PLMN ID to the access network element of the second network.

In an embodiment, a core network element of the second network sends the voice fallback indication information and/or a last used PLMN ID to an access network element of the second network through a bearer setup or release message; or, the core network element of the second network sends the voice fallback indication information and/or the last used PLMN ID to the access network element of the second network through the initial context setup request message.

In an embodiment, the core network element of the second network receives the voice fallback indication information and/or the last used PLMN ID sent by the core network element of the first network, and the core network element of the second network sends the voice fallback indication information and/or the last used PLMN ID to the access network element of the second network.

Step 602: after the terminal completes the voice service in the second network, the second network sends a switching or redirection message to the terminal based on the voice fallback indication information and/or the last used PLMN ID, so as to trigger the terminal to switch from the second network or redirect to the first network.

In an embodiment, after the terminal completes the voice service in the second network, the access network element of the second network completes bearer release, and sends a handover or redirection message to the terminal.

In an embodiment, after the terminal completes the voice service in the second network, the core network element of the second network completes bearer release, and sends a handover or redirection message to the terminal.

And after the second network sends a switching or redirection message, selecting the first network as a target network of the terminal.

In an embodiment, the method further comprises: determining cell information and/or frequency information of the target network.

In an embodiment, the first network is selected as the target network for the terminal based on the last used PLMN ID.

In an embodiment, after the terminal completes a voice service in the second network and completes bearer release, the access network element of the second network sends an RRC release message to the terminal, so that the terminal releases an RRC connection to enter an idle state, performs cell reselection through an RFSP policy, and returns to the first network.

In an embodiment, after the terminal completes the voice service in the second network and completes bearer release, the core network element of the second network sends an RRC release message to the terminal, so that the terminal releases an RRC connection to enter an idle state, performs cell reselection through an RFSP policy, and returns to the first network.

Fig. 7 is a schematic structural diagram of a network returning apparatus according to an embodiment of the present invention, where the apparatus of this embodiment is applied to a terminal, and as shown in fig. 7, the network returning apparatus includes:

a first network changing unit 701, configured to switch or redirect from a first network to a second network, and perform a voice service in the second network;

a determining unit 702, configured to determine, in a process of switching or redirecting the terminal from the first network to the second network, that a cause value of the switching or redirecting is voice fallback, where the cause value is used to indicate that the switching or redirecting is caused by the voice fallback;

a first sending unit 703, configured to send, by the second network, voice fallback indication information and/or a last used PLMN ID;

a first receiving unit 704, configured to receive a handover or redirection message sent by the second network after completing a voice service in the second network;

a second network changing unit 705, configured to switch or redirect from the second network to the first network based on the handover or redirection message.

In one embodiment, in the case where the terminal is handed over from the first network to the second network:

the device further comprises: a second receiving unit 706, configured to receive a handover command sent by the first network, where the handover command carries voice fallback indication information;

the determining unit 702 is configured to determine, based on the handover command, that a cause value of the handover is a voice fallback, where the cause value is used to indicate that the handover is caused by the voice fallback.

In an embodiment, the first network changing unit 701 is configured to switch from a first access network to a second access network, and maintain a connection with a first core network.

In one embodiment, the first network changing unit 701 switches from a first access network to a second access network and switches from a first core network to a second core network.

In an embodiment, in case the terminal is redirected from the first network to the second network:

the device further comprises: a third receiving unit 707, configured to receive a redirection message sent by the first network, where the redirection message carries voice fallback indication information;

the determining unit 702 is configured to determine, based on the redirection message, that a cause value of the redirection is a voice fallback, where the cause value is used to indicate that the redirection is caused by the voice fallback.

In one embodiment, the apparatus further comprises: a second sending unit 708, configured to send a SIP invite message;

the determining unit 702 is configured to determine, after sending the SIP invite message, that a cause value of the handover or redirection is a voice fallback if a handover command or an RRC connection release message sent by the first network is received within a first time period, where the cause value is used to indicate that the handover or redirection is caused by the voice fallback.

In an embodiment, the first sending unit 703 is configured to send an AS parameter in an AS message and/or an NAS message to the second network, where the AS parameter in the AS message and/or the NAS message carries the voice fallback indication information and/or the last used PLMN ID.

In an embodiment, the first sending unit 703 is configured to send a NAS message to the second network, where the NAS message carries voice fallback indication information and/or a last used PLMN ID.

In an embodiment, the sending, by a core network element of the second network, the voice fallback indication information and/or a last used PLMN ID to an access network element of the second network includes:

In an embodiment, a core network element of the first network sends a request message for establishing a voice QoS flow to an access network element of the first network, and receives a reject message sent by the access network element of the first network, where the reject message carries a cause value, and the cause value is used to indicate that the reject message is caused by the voice fallback; if the core network element of the first network receives the handover request message sent by the access network element of the first network within a first time period, the core network element of the first network determines that the reason for the handover request message is caused by the voice fallback.

In an embodiment, after the terminal completes the voice service in the second network, the access network element of the second network completes bearer release, and the first receiving unit 704 receives a handover or redirection message sent by the access network element of the second network.

In an embodiment, after the terminal completes the voice service in the second network, the core network element of the second network completes bearer release, and the first receiving unit 704 receives a handover or redirection message sent by the core network element of the second network.

In an embodiment, after the second network sends a handover or redirection message, the first network is selected as a target network of the terminal.

In an embodiment, after the first network is selected as the target network of the terminal, cell information and/or frequency information of the target network is determined.

In an embodiment, after the terminal completes the voice service in the second network and completes bearer release, the first receiving unit 704 receives an RRC release message sent by an access network element of the second network, releases an RRC connection to enter an idle state, performs cell reselection through an RFSP policy, and returns the cell reselection to the first network.

In an embodiment, after the terminal completes the voice service in the second network and completes bearer release, the first receiving unit 704 receives an RRC release message sent by a core network element of the second network, releases an RRC connection to enter an idle state, performs cell reselection through an RFSP policy, and returns the cell reselection to the first network.

Those skilled in the art will understand that the implementation functions of each unit in the network returning device shown in fig. 7 can be understood by referring to the related description of the network returning method. The functions of the units in the network returning apparatus shown in fig. 7 may be implemented by a program running on a processor, or may be implemented by specific logic circuits.

Fig. 8 is a schematic structural diagram of a network returning apparatus according to an embodiment of the present invention, where the apparatus according to the embodiment is applied to a network, and as shown in fig. 8, the network returning apparatus includes:

a receiving unit 801, configured to receive, during a handover or redirection process of a terminal from a first network to a second network, voice fallback indication information and/or a last used PLMN ID sent by the terminal;

a sending unit 802, configured to send a handover or redirection message to the terminal based on the voice fallback indication information and/or the last used PLMN ID after the terminal completes a voice service in the second network, so as to trigger the terminal to handover from the second network or redirect to the first network.

In an embodiment, the receiving unit 801 is configured to receive an AS parameter in an AS message and/or an NAS message sent by the terminal, where the AS parameter in the AS message and/or the NAS message carries voice fallback indication information and/or a last used PLMN ID; and acquiring the voice fallback indication information and/or the last used PLMN ID from the AS parameters in the AS message and/or the NAS message.

In an embodiment, the receiving unit 801 is configured to receive an NAS message sent by the terminal, where the NAS message carries voice fallback indication information and/or a last used PLMN ID; and acquiring the voice fallback indication information and/or the last used PLMN ID from the NAS message, and sending the voice fallback indication information and/or the last used PLMN ID to an access network element of the second network.

In one embodiment, the apparatus further comprises:

a selecting unit 803, configured to select the first network as a target network of the terminal.

In one embodiment, the apparatus further comprises: a determining unit 804, configured to determine cell information and/or frequency information of the target network.

In an embodiment, the selecting unit 803 is configured to select the first network as a target network of the terminal based on the last used PLMN ID.

In an embodiment, the handover or redirection message sent by the sending unit 802 to the terminal carries cell information and/or frequency information of the first network.

Those skilled in the art will understand that the implementation functions of each unit in the network returning device shown in fig. 8 can be understood by referring to the related description of the network returning method. The functions of the units in the network returning apparatus shown in fig. 8 may be implemented by a program running on a processor, or may be implemented by specific logic circuits.

The network returning device according to the embodiment of the present invention may be stored in a computer-readable storage medium if it is implemented in the form of a software function module and sold or used as an independent product. Based on such understanding, the technical solutions of the embodiments of the present invention may be essentially implemented or a part contributing to the prior art may be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the methods described in the embodiments of the present invention. And the aforementioned storage medium includes: various media capable of storing program codes, such as a usb disk, a removable hard disk, a Read Only Memory (ROM), a magnetic disk, or an optical disk. Thus, embodiments of the invention are not limited to any specific combination of hardware and software.

Accordingly, the embodiment of the present invention further provides a computer storage medium, in which computer executable instructions are stored, and when the computer executable instructions are executed by a processor, the network return method of the embodiment of the present invention is implemented.

Fig. 9 is a schematic structural diagram of a computer device according to an embodiment of the present invention, where the computer device may be a terminal or a network device. As shown in fig. 9, the computer device 100 may include one or more processors 1002 (only one of which is shown in the figure), the processors 1002 may include, but are not limited to, a processing device such as a Microprocessor (MCU) or a Programmable logic device (FPGA), a memory 1004 for storing data, and a transmission device 1006 for communication functions. It will be understood by those skilled in the art that the structure shown in fig. 9 is only an illustration and is not intended to limit the structure of the electronic device. For example, computer device 100 may also include more or fewer components than shown in FIG. 9, or have a different configuration than shown in FIG. 9.

The memory 1004 can be used for storing software programs and modules of application software, such as program instructions/modules corresponding to the method in the embodiment of the present invention, and the processor 1002 executes various functional applications and data processing by running the software programs and modules stored in the memory 1004, so as to implement the method described above. The memory 1004 may include high-speed random access memory, and may also include non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some examples, the memory 1004 may further include memory located remotely from the processor 1002, which may be connected to the computer device 100 via a network. Examples of such networks include, but are not limited to, the internet, intranets, local area networks, mobile communication networks, and combinations thereof.

The transmission device 1006 is used for receiving or sending data via a network. Specific examples of such networks may include wireless networks provided by the communications provider of the computer device 100. In one example, the transmission device 1006 includes a Network adapter (NIC) that can be connected to other Network devices through a base station so as to communicate with the internet. In one example, the transmission device 1006 can be a Radio Frequency (RF) module, which is used for communicating with the internet in a wireless manner.

The technical schemes described in the embodiments of the present invention can be combined arbitrarily without conflict.

In the embodiments provided in the present invention, it should be understood that the disclosed method and intelligent device may be implemented in other ways. The above-described device embodiments are merely illustrative, for example, the division of the unit is only a logical functional division, and there may be other division ways in actual implementation, such as: multiple units or components may be combined, or may be integrated into another system, or some features may be omitted, or not implemented. In addition, the coupling, direct coupling or communication connection between the components shown or discussed may be through some interfaces, and the indirect coupling or communication connection between the devices or units may be electrical, mechanical or other forms.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, that is, may be located in one place, or may be distributed on a plurality of network units; some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, all the functional units in the embodiments of the present invention may be integrated into one second processing unit, or each unit may be separately regarded as one unit, or two or more units may be integrated into one unit; the integrated unit can be realized in a form of hardware, or in a form of hardware plus a software functional unit.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention.

Claims

1. A network return method, the method comprising:

a terminal redirects from a first network to a second network, and performs voice service in the second network, wherein in the process of redirecting from the first network to the second network, the terminal receives a redirection message sent by the first network, and the redirection message carries voice fallback indication information; the terminal determines that a reason value of the redirection is voice fallback based on the redirection message, wherein the reason value is used for indicating that the redirection is caused by the voice fallback, and sends voice fallback indication information and/or a last used public land mobile network identity (PLMN ID) to the second network;

after the terminal completes voice service in the second network, the terminal receives a redirection message sent by the second network, and redirects the terminal from the second network to the first network based on the redirection message;

the terminal sending the voice fallback indication information and/or the last used PLMN ID to the second network, including:

and the terminal sends the AS parameters in the AS message and/or the NAS message to the second network, wherein the AS parameters in the AS message and/or the NAS message carry the voice fallback indication information and/or the PLMN ID used last.

2. The method of claim 1, wherein the redirection message is an N2 request message, or an RRC connection release message.

3. The method of claim 1, wherein the terminal determines that a cause value of the redirection is a voice fallback, the cause value indicating that the redirection is due to the voice fallback, comprising:

after the terminal sends a Session Initiation Protocol (SIP) invitation message, if a handover command or a Radio Resource Control (RRC) connection release message sent by the first network is received within a first time period, determining that a reason value of the redirection is voice fallback, wherein the reason value is used for indicating that the redirection is caused by the voice fallback.

4. The method of claim 1, wherein the AS message comprises at least one of: RRC connection request message, handover complete message, RRC connection setup complete message.

5. The method of claim 1, wherein the AS parameters in the NAS message comprise at least one of: the AS parameter in the attach request message and the AS parameter in the tracking area update request message.

6. The method according to any of claims 1 to 5, wherein an access network element of the second network obtains the voice fallback indication information and/or the last used PLMN ID from AS parameters in the AS message and/or NAS message.

7. A method according to any of claims 1 to 3, wherein the terminal sending the voice fallback indication information and/or the last used PLMN ID to the second network comprises:

8. The method of claim 7, wherein the NAS message comprises at least one of: NAS message in attach request message, NAS message in tracking area update request message.

9. The method according to claim 7, wherein a core network element of the second network obtains the voice fallback indication information and/or the last used PLMN ID from the NAS message, and sends the voice fallback indication information and/or the last used PLMN ID to an access network element of the second network.

10. The method of claim 9, wherein the sending, by the core network element of the second network, the voice fallback indication information and/or the last used PLMN ID to the access network element of the second network comprises:

11. The method according to any one of claims 1 to 3, wherein a core network element of the second network receives the voice fallback indication information and/or the last used PLMN ID sent by the core network element of the first network, and the core network element of the second network sends the voice fallback indication information and/or the last used PLMN ID to an access network element of the second network.

12. The method of claim 1, wherein after the terminal completes the voice service in the second network, an access network element of the second network completes bearer release, and the terminal receives a redirection message sent by the second network.

13. The method of claim 1, wherein after the terminal completes the voice service in the second network, a core network element of the second network completes bearer release, and the terminal receives a redirection message sent by the second network element.

14. A method according to claim 12 or 13, wherein the second network selects the first network as the target network for the terminal after sending a redirect message.

15. The method of claim 14, wherein the method further comprises: determining cell information and/or frequency information of the target network.

16. The method of claim 12, wherein the first network is selected as a target network for the terminal based on the last used PLMN ID.

17. The method according to any one of claims 1 to 5, wherein after the terminal completes the voice service in the second network and completes bearer release, the terminal receives an RRC release message sent by an access network element of the second network, releases an RRC connection to enter an idle state, performs cell reselection through a radio resource management, RFSP, policy, and returns to the first network.

18. The method according to any one of claims 1 to 5, wherein after the terminal completes the voice service in the second network and completes bearer release, the terminal receives an RRC release message sent by a core network element of the second network, releases an RRC connection to enter an idle state, performs cell reselection through a radio resource management, RFSP, policy, and returns to the first network.

19. A network return method, the method comprising:

in the process that the terminal is redirected from a first network to a second network, the second network receives voice fallback indication information and/or a last used PLMN ID sent by the terminal;

after the terminal completes voice service in the second network, the second network sends a redirection message to the terminal based on the voice fallback indication information and/or the last used PLMN ID so as to trigger the terminal to redirect from the second network to the first network;

wherein, the second network receiving the voice fallback indication information and/or the last used PLMN ID sent by the terminal includes:

20. The method of claim 19, wherein the AS message comprises at least one of: RRC connection request message, handover complete message, RRC connection setup complete message.

21. The method of claim 19, wherein the AS parameters in the NAS message comprise at least one of: the AS parameter in the attach request message and the AS parameter in the tracking area update request message.

22. The method according to any of claims 19 to 21, wherein an access network element of the second network obtains the voice fallback indication information and/or the last used PLMN ID from AS parameters in the AS message and/or NAS message.

23. The method of claim 19, wherein the second network receiving the voice fallback indication information and/or the last used PLMN ID sent by the terminal comprises:

24. The method of claim 23, wherein the NAS message comprises at least one of: NAS message in attach request message, NAS message in tracking area update request message.

25. The method according to claim 23 or 24, wherein a core network element of the second network obtains the voice fallback indication information and/or the last used PLMN ID from the NAS message, and sends the voice fallback indication information and/or the last used PLMN ID to an access network element of the second network.

26. The method of claim 25, wherein the sending, by the core network element of the second network, the voice fallback indication information and/or the last used PLMN ID to the access network element of the second network comprises:

27. The method according to any one of claims 19 to 21, wherein a core network element of the second network receives the voice fallback indication information and/or the last used PLMN ID sent by the core network element of the first network, and the core network element of the second network sends the voice fallback indication information and/or the last used PLMN ID to an access network element of the second network.

28. The method of claim 19, wherein after the terminal completes the voice service in the second network, an access network element of the second network completes bearer release and sends a redirection message to the terminal.

29. The method of claim 19, wherein after the terminal completes the voice service in the second network, a core network element of the second network completes bearer release and sends a redirection message to the terminal.

30. A method according to claim 28 or 29, wherein the second network selects the first network as the target network for the terminal after sending a redirect message.

31. The method of claim 30, wherein the method further comprises: determining cell information and/or frequency information of the target network.

32. The method of claim 30, wherein the first network is selected as a target network for the terminal based on the last used PLMN ID.

33. The method according to any one of claims 19 to 21, wherein after the terminal completes a voice service in the second network and completes bearer release, an access network element of the second network sends an RRC release message to the terminal, so that the terminal releases an RRC connection to enter an idle state, performs cell reselection through an RFSP policy, and returns to the first network.

34. The method according to any one of claims 19 to 21, wherein after the terminal completes a voice service in the second network and completes bearer release, a core network element of the second network sends an RRC release message to the terminal, so that the terminal releases an RRC connection to enter an idle state, performs cell reselection through an RFSP policy, and returns to the first network.

35. A network returning device applied to a terminal, the device comprising:

a first network changing unit, configured to redirect from a first network to a second network, and perform a voice service in the second network;

a third receiving unit, configured to receive a redirection message sent by the first network in a process that the terminal redirects from the first network to the second network, where the redirection message carries voice fallback indication information;

a determining unit, configured to determine, based on the redirection message, that a cause value of the redirection is a voice fallback, where the cause value is used to indicate that the redirection is caused by the voice fallback;

a first sending unit, configured to send voice fallback indication information and/or a last used PLMN ID to the second network;

a first receiving unit, configured to receive a redirection message sent by the second network after completing a voice service in the second network;

a second network changing unit configured to redirect from the second network to the first network based on the redirection message;

the first sending unit is configured to send an AS parameter in an AS message and/or an NAS message to the second network, where the AS parameter in the AS message and/or the NAS message carries voice fallback indication information and/or a last used PLMN ID.

36. The apparatus of claim 35, wherein the redirection message is an N2 request message, or an RRC connection release message.

37. The apparatus of claim 35, wherein the apparatus further comprises: a second sending unit, configured to send an SIP invite message;

the determining unit is configured to determine that a cause value of the redirection is a voice fallback if a handover command or an RRC connection release message sent by the first network is received within a first time period after the SIP invite message is sent, where the cause value is used to indicate that the redirection is caused by the voice fallback.

38. The apparatus of claim 35, wherein the AS message comprises at least one of: RRC connection request message, handover complete message, RRC connection setup complete message.

39. The apparatus of claim 35, wherein AS parameters in the NAS message comprise at least one of: the AS parameter in the attach request message and the AS parameter in the tracking area update request message.

40. The apparatus according to any of claims 35 to 39, wherein an access network element of the second network obtains the voice fallback indication information and/or the last used PLMN ID from AS parameters in the AS message and/or NAS message.

41. The apparatus according to any one of claims 35 to 37, wherein the first sending unit is configured to send a NAS message to the second network, where the NAS message carries voice fallback indication information and/or a last used PLMN ID.

42. The apparatus of claim 41, wherein the NAS message comprises at least one of: NAS message in attach request message, NAS message in tracking area update request message.

43. The apparatus of claim 41, wherein a core network element of the second network obtains the voice fallback indication information and/or the last used PLMN ID from the NAS message and sends the voice fallback indication information and/or the last used PLMN ID to an access network element of the second network.

44. The apparatus of claim 43, wherein the sending, by the core network element of the second network, the voice fallback indication information and/or the last used PLMN ID to the access network element of the second network comprises:

45. The apparatus according to any one of claims 35 to 37, wherein a core network element of the second network receives the voice fallback indication information and/or the last used PLMN ID sent by the core network element of the first network, and the core network element of the second network sends the voice fallback indication information and/or the last used PLMN ID to an access network element of the second network.

46. The apparatus of claim 35, wherein after the terminal completes the voice service in the second network, the access network element of the second network completes bearer release, and the first receiving unit receives a redirection message sent by the access network element of the second network.

47. The apparatus of claim 35, wherein after the terminal completes the voice service in the second network, the core network element of the second network completes bearer release, and the first receiving unit receives a redirection message sent by the core network element of the second network.

48. The apparatus of claim 46 or 47, wherein the second network selects the first network as a target network for the terminal after sending a redirect message.

49. The apparatus of claim 48, wherein the selection of the first network as a target network for the terminal is followed by a determination of cell information and/or frequency information for the target network.

50. The apparatus of claim 46, wherein the first network is selected as a target network for the terminal based on the last used PLMN ID.

51. The apparatus of any one of claims 35 to 39, wherein after the terminal completes a voice service in the second network and completes bearer release, the first receiving unit receives an RRC release message sent by an access network element of the second network, releases an RRC connection to enter an idle state, performs cell reselection through a radio resource management (RFSP) policy, and returns to the first network.

52. The apparatus according to any one of claims 35 to 39, wherein after the terminal completes a voice service in the second network and completes bearer release, the first receiving unit receives an RRC release message sent by a core network element of the second network, releases an RRC connection to enter an idle state, performs cell reselection through a radio resource management (RFSP) policy, and returns to the first network.

53. A network return apparatus applied to a network, the apparatus comprising:

a receiving unit, configured to receive, in a process of redirecting a terminal from a first network to a second network, voice fallback indication information and/or a last used PLMN ID sent by the terminal;

a sending unit, configured to send, after the terminal completes a voice service in the second network, a redirection message to the terminal based on the voice fallback indication information and/or a last used PLMN ID, so as to trigger the terminal to redirect from the second network to the first network;

the receiving unit is configured to receive an AS parameter in an AS message and/or an NAS message sent by the terminal, where the AS parameter in the AS message and/or the NAS message carries voice fallback indication information and/or a last used PLMN ID; and acquiring the voice fallback indication information and/or the last used PLMN ID from the AS parameters in the AS message and/or the NAS message.

54. The apparatus of claim 53, wherein the AS message comprises at least one of: RRC connection request message, handover complete message, RRC connection setup complete message.

55. The apparatus of claim 53, wherein the AS parameters in the NAS message comprise at least one of: the AS parameter in the attach request message and the AS parameter in the tracking area update request message.

56. The apparatus according to any of claims 53 to 55, wherein an access network element of the second network obtains the voice fallback indication information and/or the last used PLMN ID from AS parameters in the AS message and/or NAS message.

57. The apparatus of claim 53, wherein the receiving unit is configured to receive a NAS message sent by the terminal, where the NAS message carries voice fallback indication information and/or a last used PLMN ID; and acquiring the voice fallback indication information and/or the last used PLMN ID from the NAS message, and sending the voice fallback indication information and/or the last used PLMN ID to an access network element of the second network.

58. The apparatus of claim 57, wherein the NAS message comprises at least one of: NAS message in attach request message, NAS message in tracking area update request message.

59. The apparatus of claim 57, wherein a core network element of the second network obtains the voice fallback indication information and/or a last used PLMN ID from the NAS message, and sends the voice fallback indication information and/or the last used PLMN ID to an access network element of the second network.

60. The apparatus of claim 59, wherein the sending, by the core network element of the second network, the voice fallback indication information and/or the last used PLMN ID to the access network element of the second network comprises:

61. The apparatus according to any one of claims 53 to 55, wherein a core network element of the second network receives the voice fallback indication information and/or the last used PLMN ID sent by the core network element of the first network, and the core network element of the second network sends the voice fallback indication information and/or the last used PLMN ID to an access network element of the second network.

62. The apparatus of claim 53, wherein after the terminal completes the voice service in the second network, an access network element of the second network completes bearer release and sends a redirection message to the terminal.

63. The apparatus of claim 53, wherein after the terminal completes the voice service in the second network, a core network element of the second network completes bearer release and sends a redirection message to the terminal.

64. The apparatus of claim 62 or 63, wherein the apparatus further comprises:

65. The apparatus of claim 64, wherein the apparatus further comprises: a determining unit, configured to determine cell information and/or frequency information of the target network.

66. The apparatus of claim 64, wherein the selection unit is configured to select the first network as a target network for the terminal based on the last used PLMN ID.

67. The apparatus according to any one of claims 53 to 55, wherein after the terminal completes a voice service in the second network and completes bearer release, the access network element of the second network sends an RRC release message to the terminal, so that the terminal releases an RRC connection to enter an idle state, performs cell reselection through an RFSP policy, and returns to the first network.

68. The apparatus according to any one of claims 53 to 55, wherein after the terminal completes a voice service in the second network and completes bearer release, a core network element of the second network sends an RRC release message to the terminal, so that the terminal releases an RRC connection to enter an idle state, performs cell reselection through an RFSP policy, and returns to the first network.

69. A computer storage medium having stored thereon computer-executable instructions which, when executed by a processor, perform the method steps of any one of claims 1 to 18, or the method steps of any one of claims 19 to 34.