TECHNICAL FIELD

This application relates to the field of communications technologies, and in particular, to a communications method, apparatus, and system.

BACKGROUND

A conventional communications system includes two parts: an access network and a core network. The access network is on edge of a mobile communications system, and is responsible for connecting terminal devices to the core network. The core network is responsible for connecting the terminal devices to different data networks (DNs), and implementing functions such as charging and mobility management. An access function of the access network is mainly implemented using a base station. The core network mainly includes the following core network devices: a mobility management network element, a session management network element, a user plane network element, and the like.

When a terminal device requests to access a data network, the core network establishes a session for the terminal device. In this way, the terminal device can transmit data to the data network based on the session, to implement communications service. When the core network establishes a session, the following procedure is performed.

First, the terminal device sends, to a base station, a request message requesting to establish a session or requesting a service, and the base station sends, to a mobility management network element, the request message sent by the terminal device. The mobility management network element determines a session management network element based on the request message, and sends a session request to the session management network element. After receiving the session request, the session management network element selects a user plane network element in a service area of the session management network element, and initiates a session establishment procedure to the user plane network element. Finally, a complete session is established.

In some scenarios, the session of the terminal device may relate to a plurality of user plane network elements, for example, an intermediate user plane network element connected to the base station and an anchor user plane network element connected to the DN. If the intermediate user plane network element and the anchor user plane network element are located in different service areas, a session management network element in a corresponding service area needs to manage the intermediate user plane network element or the anchor user plane network element respectively. In other words, an intermediate session management network element manages the intermediate user plane network element in a service area1in which the intermediate user plane network element is located, and an anchor session management network element manages the anchor user plane network element in a service area2in which the anchor user plane network element is located.

Due to mobility of the terminal device, the terminal device may move from the service area1to a service area3. In this case, in the core network, a new intermediate user plane network element in the service area3needs to be selected for re-establishing a session of the terminal device, to ensure service continuity of the terminal device. Therefore, in the core network, an intermediate session management network element in the service area3needs to manage the new intermediate user plane network element.

However, currently, there is no technical solution for implementing handover between session management network elements. Consequently, in the core network, the intermediate session management network element that manages the new intermediate user plane network element cannot be determined in the service area3. Consequently, a session cannot be re-established.

SUMMARY

This application provides a communications method, apparatus, and system, to implement handover between session management network elements.

According to a first aspect, an embodiment of this application provides a communications method, and the method may be performed by a session management network element or a chip in the session management network element. The session management network element may be a session management function (SMF) entity in 5thgeneration (5G) communication, and may be another entity having a session management function in future communication. The method includes the following steps: First, a target intermediate session management network element obtains information about a source session management network element, and then sends a first message to the source session management network element based on the information about the source session management network element. The source session management network element is a session management network element that controls a user plane network element communicatively connected with a source base station. The first message is used to establish a forwarding tunnel from a source intermediate user plane network element to a target intermediate user plane network element, the source intermediate user plane network element is a user plane network element that is controlled by the source session management network element and that is communicatively connected with the source base station, and the target intermediate user plane network element is a user plane network element that is controlled by the target intermediate session management network element and that is communicatively connected with a target base station.

According to the foregoing method, the forwarding tunnel from the source intermediate user plane network element to the target intermediate user plane network element is established, such that the source intermediate user plane network element can forward data to the target intermediate user plane network element through the forwarding tunnel, to implement handover from the target intermediate session management network element to the source session management network element, maintain a session of a terminal device, and ensure service continuity of the terminal device.

In a possible design, before the target intermediate session management network element sends the first message to the source session management network element based on the information about the source session management network element, the target intermediate session management network element may first obtain first indication information. The first indication information indicates the target intermediate session management network element to establish the forwarding tunnel.

According to the foregoing method, the target intermediate session management network element can determine, by obtaining the first indication information, that the forwarding tunnel needs to be established currently, and then establish the forwarding tunnel. This can improve flexibility and efficiency of establishing the forwarding tunnel.

In a possible design, the target intermediate session management network element obtains the first indication information in a plurality of manners, and two manners are listed.

Manner 1: The target intermediate session management network element may obtain the first indication information from the source session management network element. In this case, the target intermediate session management network element can directly interact with the source session management network element to obtain the first indication information.

Manner 2: The target intermediate session management network element obtains the first indication information from a mobility management network element.

According to the foregoing method, the first indication information may be sent by different network elements to the target intermediate session management network element. Different manners of establishing the forwarding tunnel are provided and may be applied to different scenarios, to ensure a wider range of application scenarios.

In a possible design, after obtaining the first indication information, the target intermediate session management network element may indicate, according to the first indication information, the target intermediate user plane network element to establish the forwarding tunnel.

According to the foregoing method, the first indication information is used as an indication to establish the forwarding tunnel, such that the forwarding tunnel can be successfully established, and efficiency of establishing the forwarding tunnel can be improved.

In a possible design, the first message may include information used to identify the forwarding tunnel, for example, the first message includes forwarding tunnel information corresponding to the target intermediate user plane network element.

According to the foregoing method, the first message includes the forwarding tunnel information corresponding to the target intermediate user plane network element. As such, the target intermediate session management network element can conveniently and quickly establish the forwarding tunnel.

In a possible design, to enable the target intermediate session management network element to directly interact with the source session management network element, the target intermediate session management network element needs to obtain the information about the source session management network element. For example, the target intermediate session management network element obtains the information about the source session management network element from the mobility management network element.

According to the foregoing method, the target intermediate session management network element obtains the information about the source session management network element, such that the target intermediate session management network element can directly interact with the source session management network element. A manner in which the source session management network element directly interacts with the target intermediate session management network element is relatively quick and efficient, and efficiency of establishing the forwarding tunnel can be improved.

In a possible design, after establishing the forwarding tunnel, the target intermediate session management network element sets a forwarding tunnel release timer. When the forwarding tunnel release timer expires, the target intermediate session management network element indicates the intermediate user plane network element to release the forwarding tunnel.

According to the foregoing method, the forwarding tunnel release timer is set, such that tunnel resources can be saved. When the forwarding tunnel is to be released, only whether the forwarding tunnel release timer expires needs to be determined, and the target intermediate session management network element does not need to send other signaling, such that signaling resources can be effectively saved.

In a possible design, in addition to the forwarding tunnel, a tunnel between the target intermediate user plane network element and an anchor user plane network element may be further established. A process is as follows.

The target intermediate session management network element obtains session information from the source session management network element based on the information about the source session management network element; or the target intermediate session management network element receives the session information from the mobility management network element; and the target intermediate session management network element establishes the tunnel between the target intermediate user plane network element and the anchor user plane network element based on the session information.

The session information includes at least one of the following: uplink tunnel information of the anchor user plane network element or information about an anchor session management network element, where the anchor session management network element is a session management network element that controls the anchor user plane network element.

According to the foregoing method, data that needs to be transmitted between a data network and the terminal device may be transmitted through the tunnel between the target intermediate user plane network element and the anchor user plane network element. As such, the terminal device can receive and send data in a timely manner, thereby ensuring the service continuity of the terminal device.

In a possible design, the first indication information may be carried in the session information.

According to the foregoing method, the session information and the first indication information may be sent together, such that signaling resources can be effectively saved, and efficiency can be improved.

In a possible design, the information about the source session management network element may be carried in the session information.

According to the foregoing method, the session information and the information about the source session management network element may be sent together, such that signaling resources can be effectively saved, and efficiency can be improved.

According to a second aspect, an embodiment of this application provides a communications method, and the method may be performed by a session management network element or a chip in the session management network element. The session management network element may be an SMF entity in 5G communication, and may be another entity having a session management function in future communication. The method includes the following steps: First, a source session management network element receives a first message from a target intermediate session management network element, and then indicates, based on the first message, a source intermediate user plane network element to establish a forwarding tunnel.

The first message is used to establish a forwarding tunnel from the source intermediate user plane network element to a target intermediate user plane network element, and the source intermediate user plane network element is a user plane network element that is controlled by the source session management network element and that is communicatively connected with a source base station, and the target intermediate session management network element is a session management network element that controls the target intermediate user plane network element communicatively connected with a target base station.

According to the foregoing method, the forwarding tunnel from the source intermediate user plane network element to the target intermediate user plane network element is established, such that the source intermediate user plane network element can forward data to the target intermediate user plane network element through the forwarding tunnel, to implement handover from the target intermediate session management network element to the source session management network element, maintain a session, and ensure service continuity of a terminal device.

In a possible design, before the source session management network element receives the first message from the target intermediate session management network element, the source session management network element may first determine that the forwarding tunnel needs to be established, and then send the first indication information to the target intermediate session management network element or a mobility management network element. The first indication information indicates the target intermediate session management network element to establish the forwarding tunnel.

According to the foregoing method, when determining that the forwarding tunnel needs to be established, the source session management network element sends the first indication information, to indicate the target intermediate session management network element to establish the forwarding tunnel. This can improve flexibility and efficiency of establishing the forwarding tunnel.

In a possible design, the source session management network element may determine, in a plurality of manners, that the forwarding tunnel needs to be established. When the source session management network element or the source intermediate user plane network element has downlink data to be sent to the terminal device, the source session management network element may determine that the forwarding tunnel needs to be established.

According to the foregoing method, the forwarding tunnel is established when the downlink data needs to be sent to the terminal device. The source session management network element or the source intermediate user plane network element may send the downlink data to the terminal device through the forwarding tunnel, such that the terminal device can receive the data in a timely manner.

In a possible design, the first message may include information used to identify the forwarding tunnel, for example, the first message includes forwarding tunnel information corresponding to the target intermediate user plane network element.

According to the foregoing method, the first message includes the forwarding tunnel information corresponding to the target intermediate user plane network element, such that the target intermediate session management network element can conveniently and quickly establish the forwarding tunnel.

In a possible design, after establishing the forwarding tunnel, the source session management network element may set a forwarding tunnel release timer; and when the forwarding tunnel release timer expires, the source session management network element indicates the source intermediate user plane network element to release the forwarding tunnel.

According to the foregoing method, the forwarding tunnel release timer is set, such that tunnel resources can be saved. When the forwarding tunnel is to be released, only whether the forwarding tunnel release timer expires needs to be determined, and the source session management network element does not need to send other signaling, such that signaling resources can be effectively saved.

In a possible design, in addition to the forwarding tunnel, a tunnel between the target intermediate user plane network element and an anchor user plane network element may be further established. A process is as follows.

The source session management network element sends session information to the target intermediate session management network element, such that the target intermediate session management network element establishes the tunnel between the target intermediate user plane network element and the anchor user plane network element; or the source session management network element sends session information to the mobility management network element, such that the mobility management network element sends the session information to the target intermediate session management network element.

The session information includes at least one of the following: uplink tunnel information of the anchor user plane network element or information about an anchor session management network element, where the anchor session management network element is a session management network element that controls the anchor user plane network element.

According to the foregoing method, data that needs to be transmitted between a data network and the terminal device may be transmitted through the tunnel between the target intermediate user plane network element and the anchor user plane network element. As such, the terminal device can receive and send data in a timely manner, thereby ensuring the service continuity of the terminal device.

In a possible design, the first indication information may be carried in the session information.

According to the foregoing method, the session information and the first indication information may be sent together, such that signaling resources can be effectively saved, and efficiency can be improved.

In a possible design, the information about the source session management network element may be carried in the session information.

According to the foregoing method, the session information and the information about the source session management network element may be sent together, such that signaling resources can be effectively saved, and efficiency can be improved.

According to a third aspect, an embodiment of this application provides a communications method, and the method may be performed by a mobility management entity or a chip in the mobility management entity. The mobility management entity may be an access and mobility management function (AMF) entity in 5G communication, and may be another entity having a session management function in future communication. The method includes the following steps: A mobility management network element obtains information about a target intermediate session management network element. The mobility management network element sends information about a source session management network element to the target intermediate session management network element based on the information about the target intermediate session management network element, where the source session management network element is a session management network element that controls a user plane network element communicatively connected with a source base station, and the target intermediate session management network element is a session management network element that controls a target intermediate user plane network element communicatively connected with a target base station.

According to the foregoing method, the target intermediate session management network element obtains the information about the source session management network element, such that the target intermediate session management network element can directly interact with the source session management network element.

In a possible design, the mobility management network element sends first indication information to the target intermediate session management network element. The first indication information indicates the target intermediate session management network element to establish a forwarding tunnel from a source intermediate user plane network element to the target intermediate user plane network element, and the source intermediate user plane network element is a user plane network element that is controlled by the source session management network element and that is communicatively connected with the source base station.

According to the foregoing method, the mobility management network element indicates, by sending the first indication information, the target intermediate session management network element to establish the forwarding tunnel, such that flexibility and efficiency of establishing the forwarding tunnel can be improved.

In a possible design, before the mobility management network element sends the first indication information to the target intermediate session management network element, the mobility management network element may first determine that the forwarding tunnel needs to be established. Alternatively, the mobility management network element may obtain the first indication information from the source session management network element.

According to the foregoing method, the mobility management network element may determine the first indication information in different manners, and different manners of establishing the forwarding tunnel are provided and may be applied to different scenarios, to ensure a wider range of application scenarios.

In a possible design, if the mobility management network element receives, from the source session management network element, a message used to trigger a service request procedure, the mobility management network element determines that the forwarding tunnel needs to be established.

According to the foregoing method, when the service request procedure needs to be triggered, the forwarding tunnel is established. The source session management network element may establish a session using the forwarding tunnel, to ensure that a terminal device can receive data in a timely manner.

In a possible design, the mobility management network element may obtain the information about the target intermediate session management network element in a plurality of manners. The following lists two manners.

Manner 1: The mobility management network element first obtains location information of the terminal device, and then selects the information about the target intermediate session management network element based on the location information of the terminal device.

Manner 2: The mobility management network element receives the information about the target intermediate session management network element from the source session management network element.

According to the foregoing method, the information about the target intermediate session management network element is obtained in different manners, and a plurality of manners of establishing the forwarding tunnel are provided. As such, the communications method is applied to more scenarios.

In a possible design, in addition to the forwarding tunnel, a tunnel between the target intermediate user plane network element and an anchor user plane network element may be further established. A process is as follows.

The mobility management network element receives session information from the source session management network element, and the mobility management network element sends the session information to the target intermediate session management network element. As such, the target intermediate session management network element establishes the tunnel between the target intermediate user plane network element and the anchor user plane network element.

The session information includes at least one of the following: uplink tunnel information of the anchor user plane network element or information about an anchor session management network element, where the anchor session management network element is a session management network element that controls the anchor user plane network element.

According to the foregoing method, data that needs to be transmitted between a data network and the terminal device may be transmitted through the tunnel between the target intermediate user plane network element and the anchor user plane network element. As such, the terminal device can receive and send data in a timely manner, thereby ensuring the service continuity of the terminal device.

In a possible design, the first indication information may be carried in the session information.

According to the foregoing method, the session information and the first indication information may be sent together. As such, signaling resources can be effectively saved, and efficiency can be improved.

In a possible design, the information about the source session management network element may be carried in the session information.

According to the foregoing method, the session information and the information about the source session management network element may be sent together. As such, signaling resources can be effectively saved, and efficiency can be improved.

According to a fourth aspect, an embodiment of the present disclosure provides a communications system. For beneficial effects, refer to the descriptions of the first aspect and the second aspect. Details are not described herein again. The communications system includes a target intermediate session management network element and a source session management network element.

The target intermediate session management network element is configured to obtain information about the source session management network element, and send a first message to the source session management network element based on the information about the source session management network element. The source session management network element is configured to receive the first message from the target intermediate session management network element, and indicate, based on the first message, the source intermediate user plane network element to establish the forwarding tunnel.

The first message is used to establish a forwarding tunnel from the source intermediate user plane network element to a target intermediate user plane network element, where the source intermediate user plane network element is a user plane network element that is controlled by the source session management network element and that is communicatively connected with a source base station. The target intermediate user plane network element is a user plane network element that is controlled by the target intermediate session management network element and that is communicatively connected with a target base station.

In a possible design, before receiving the first message from the target intermediate session management network element, the source session management network element determines that the forwarding tunnel needs to be established, and sends first indication information to the target intermediate session management network element. The first indication information indicates the target intermediate session management network element to establish the forwarding tunnel.

In a possible design, the target intermediate session management network element obtains the first indication information from the source session management network element, and then indicates, according to the first indication information, the target intermediate user plane network element to establish the forwarding tunnel.

In a possible design, the source session management network element sends session information to the target intermediate session management network element, where the session information includes at least one of the following: uplink tunnel information of an anchor user plane network element or information about an anchor session management network element, where the anchor session management network element is a session management network element that controls the anchor user plane network element.

In a possible design, the target intermediate session management network element may further obtain the session information from the source session management network element based on the information about the source session management network element, and then establish tunnel between the target intermediate user plane network element and the anchor user plane network element based on the session information.

In a possible design, the communications system further includes a mobility management network element, and the mobility management network element determines that the forwarding tunnel needs to be established. Optionally, the first indication information is sent to the target intermediate session management network element. The first indication information indicates the target intermediate session management network element to establish the forwarding tunnel.

In a possible design, if the mobility management network element receives, from the source session management network element, a message used to trigger a service request procedure, the mobility management network element determines that the forwarding tunnel needs to be established.

It should be understood that names of the target intermediate session management network element, the source session management network element, and the mobility management network element in the communications system constitute no limitation on devices. In another network, the target intermediate session management network element, the source session management network element, and the mobility management network element may also be other network elements having corresponding functions.

According to a fifth aspect, an embodiment of this application further provides a communications apparatus. The apparatus is applied to a session management network element. For beneficial effects, refer to the descriptions of the first aspect. Details are not described herein again. The apparatus has functions of implementing actions in the method instance of the first aspect. The functions may be implemented by hardware, or may be implemented by hardware executing corresponding software. The hardware or the software includes one or more modules corresponding to the foregoing functions. In a possible design, a structure of the apparatus includes a processing unit and a transceiver unit. These units can execute corresponding functions in the foregoing method example of the first aspect. For details, refer to the detailed descriptions of the method example. Details are not described herein again.

According to a sixth aspect, an embodiment of this application further provides a communications apparatus. The apparatus is applied to a session management network element. For beneficial effects, refer to the descriptions of the second aspect. Details are not described herein again. The apparatus has functions of implementing actions in the method instance of the second aspect. The functions may be implemented by hardware, or may be implemented by hardware executing corresponding software. The hardware or the software includes one or more modules corresponding to the foregoing functions. In a possible design, a structure of the apparatus includes a processing unit and a transceiver unit. These units can execute corresponding functions in the foregoing method example of the second aspect. For details, refer to the detailed descriptions of the method example. Details are not described herein again.

According to a seventh aspect, an embodiment of this application further provides a communications apparatus. The apparatus is applied to a mobility management network element. For beneficial effects, refer to the descriptions of the third aspect. Details are not described herein again. The apparatus has functions of implementing actions in the method instance of the third aspect. The functions may be implemented by hardware, or may be implemented by hardware executing corresponding software. The hardware or the software includes one or more modules corresponding to the foregoing functions. In a possible design, a structure of the apparatus includes a processing unit and a transceiver unit. These units can execute corresponding functions in the foregoing method example of the third aspect. For details, refer to the detailed descriptions of the method example. Details are not described herein again.

According to an eighth aspect, an embodiment of this application further provides an apparatus. The apparatus is applied to a session management network element. For beneficial effects, refer to the descriptions of the first aspect. Details are not described herein again. A structure of the communications apparatus includes a processor and a memory. The processor is configured to support the apparatus in performing a corresponding function in the method of the first aspect. The memory is coupled to the processor, and stores a program instruction and data that are necessary for the terminal. A structure of the communications apparatus further includes a communications interface configured to communicate with another device.

According to a ninth aspect, an embodiment of this application further provides an apparatus. The apparatus is applied to a session management network element. For beneficial effects, refer to the descriptions of the second aspect. Details are not described herein again. A structure of the communications apparatus includes a processor and a memory. The processor is configured to support the apparatus in performing a corresponding function in the method of the second aspect. The memory is coupled to the processor, and stores a program instruction and data that are necessary for the terminal. A structure of the communications apparatus further includes a communications interface configured to communicate with another device.

According to a tenth aspect, an embodiment of this application further provides an apparatus. The apparatus is applied to a mobility management network element. For beneficial effects, refer to the descriptions of the third aspect. Details are not described herein again. A structure of the communications apparatus includes a processor and a memory. The processor is configured to support the apparatus in performing a corresponding function in the method of the third aspect. The memory is coupled to the processor, and stores a program instruction and data that are necessary for the terminal. A structure of the communications apparatus further includes a communications interface configured to communicate with another device.

According to an eleventh aspect, this application further provides a computer-readable storage medium. The computer-readable storage medium stores an instruction, and when the instruction is run on a computer, the computer is enabled to perform the methods according to the foregoing aspects.

According to a twelfth aspect, this application further provides a computer program product including an instruction. When the instruction is run on a computer, the computer is enabled to perform the methods according to the foregoing aspects.

According to a thirteenth aspect, this application further provides a computer chip. The chip is connected to a memory. The chip is configured to read and execute a software program stored in the memory, to perform the methods according to the foregoing aspects.

