Network handover method and apparatus of voice service

A first mobility management network element in a first network for handing over a voice service of a terminal device, wherein the first mobility management network element is an access and mobility management function (AMF) network element, wherein the first network is a fifth-generation (5G) network, and wherein the first mobility management network element comprises:

• a memory configured to store computer program instructions;
• and
• a processor coupled to the memory and configured to execute the computer program instructions to cause the first mobility management network element to:
• receive first information from an access network device in the first network, wherein the first information indicates a handover of the terminal device from the first network to a second network, wherein the handover is a single radio voice call continuity (SRVCC) handover, and wherein the second network is a second-generation (2G) network or a third-generation (3G) network;
• skip, based on the first information, an operation of sending a session management context request to a session management network element in the first network, wherein the first information comprises at least one of a first identifier of a voice handover from the first network to the second network or a target identifier of the second network;
• and
• send, based on the first information, second information to a second mobility management network element in a third network,
• wherein the second information instructs the second mobility management network element to send a handover request to a mobile switching network element in the second network,
• wherein the handover request is a packet-switched to circuit-switched request message,
• wherein the handover request requests handing over the voice service to the second network,
• wherein the second mobility management network element is a mobility management entity (MME) network element,
• wherein the third network is an Evolved Packet System (EPS) network, and
• wherein the mobile switching network element is a mobile switching center (MSC) network element.

A computer program product comprising computer-executable instructions that are stored on a non-transitory computer-readable medium and that, when executed by a processor, cause a first mobility management network element in a first network to:

• receive first information from an access network device in the first network, wherein the first information indicates a handover of a terminal device from the first network to a second network, wherein the handover is a single radio voice call continuity (SRVCC) handover, wherein the second network is a second-generation (2G) network or a third-generation (3G) network, wherein the first mobility management network element is an access and mobility management function (AMF) network element, and wherein the first network is a fifth-generation (5G) network;
• skip, based on the first information, an operation of sending a session management context request to a session management network element in the first network, wherein the first information comprises at least one of a first identifier of a voice handover from the first network to the second network or a target identifier of the second network;
• and
• send, based on the first information, second information to a second mobility management network element in a third network,
• wherein the second information instructs the second mobility management network element to send a handover request to a mobile switching network element in the second network,
• wherein the handover request is a packet-switched to circuit-switched request message,
• wherein the handover request requests handing over a voice service of the terminal device to the second network,
• wherein the second mobility management network element is a mobility management entity (MME) network element,
• wherein the third network is an Evolved Packet System (EPS) network, and
• wherein the mobile switching network element is a mobile switching center (MSC) network element.

A network handover method of a voice service of a terminal device, wherein the network handover method comprises:

• receiving, by a first mobility management network element in a first network, first information from an access network device in the first network, wherein the first mobility management network element is an access and mobility management function (AMF) network element, wherein the first network is fifth-generation (5G) network, wherein the first information indicates a handover of the terminal device from the first network to a second network, wherein the handover is a single radio voice call continuity (SRVCC) handover, and wherein the second network is a second-generation (2G) network or a third-generation (3G) network;
• skipping, by the first mobility management network element based on the first information, an operation of sending a session management context request to a session management network element in the first network, wherein the first information comprises at least one of a first identifier of a voice handover from the first network to the second network or a target identifier of the second network;
• sending, by the first mobility management network element based on the first information, second information to a second mobility management network element in a third network, wherein the second information instructs the second mobility management network element to send a handover request to a mobile switching network element in the second network, wherein the handover request is a packet-switched to circuit-switched request message, wherein the handover request requests handing over the voice service to the second network, wherein the second mobility management network element is a mobility management entity (MME) network element, wherein the third network is an Evolved Packet System (EPS) network, and wherein the mobile switching network element is a mobile switching center (MSC) network element;
• determining, by the first mobility management network element, that the handover of the terminal device from the first network to the second network is completed;
• sending, by the first mobility management network element, a session deletion request to the session management network element in the first network;
• and
• deleting, by the session management network element, stored session management context information of the terminal device in the first network.

A system comprising:

• a session management network element in a first network, wherein the first network is a fifth-generation (5G) network;
• and
• a first mobility management network element in the first network, wherein the first mobility management network element is an access and mobility management function (AMF) network element and configured to:
• receive first information from an access network device in the first network, wherein the first information indicates a handover of a terminal device from the first network to a second network, wherein the handover is a single radio voice call continuity (SRVCC) handover, and wherein the second network is a second-generation (2G) network or a third-generation (3G) network;
• skip, based on the first information, a session management context operation with the session management network element in the first network, wherein the first information comprises at least one of a first identifier of a voice handover from the first network to the second network or a target identifier of the second network;
• and
• send, based on the first information, second information to a second mobility management network element in a third network,
• wherein the second information instructs the second mobility management network element to send a handover request to a mobile switching network element in the second network,
• wherein the handover request is a packet-switched to circuit-switched request message,
• wherein the handover request requests handing over a voice service of the terminal device to the second network,
• wherein the second mobility management network element is a mobility management entity (MME) network element,
• wherein the third network is an Evolved Packet System (EPS) network, and
• wherein the mobile switching network element is a mobile switching center (MSC) network element.