A mobility management method and apparatus, device, communication system, and storage medium

Abstract

The application discloses a mobility management method and device, equipment, a communication system and a storage medium. The method comprises the following steps: sending a PDN connection request of a first communication network; wherein the PDN connection request comprises first PDU session information of a PDU session established by a terminal device on a second communication network; receiving a PDN connection response corresponding to the PDN connection request, and establishing a PDN connection on the first communication network; wherein the PDN connection response comprises second PDU session information determined according to the first PDU session information; and saving the second PDU session information. In this way, when the terminal device activates the PDN connection, the terminal device and the network share the PDU session information through the PDN connection request and the PDN connection response, and when the terminal device switches from the first communication network to the second communication network, the PDU session is directly established by using the saved second PDU session information, so that the modification process of the PDU session is not needed, and air interface resources are saved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mobile communication, and in particular to a mobility management method and device, equipment, a communication system, and a storage medium. BACKGROUND

[0002] Since the current fourth generation (4G) network coverage is already very comprehensive and can meet the needs of most people, operators now choose a mixed networking mode of fifth generation (5G) network and 4G network, which can meet people's daily life needs and gradually build 5G network under the condition of saving costs. From the current networking situation, 4G network and 5G network are a long-term coexistence process. In order to realize the smooth transition of services, the N26 interface is added between the 4G core network mobility management entity (MME) and the 5G core network access and mobility management function (AMF).

[0003] A protocol data unit (PDU) session is established between the terminal and the 5G network when there is data transmission, and a packet data network (PDN) connection is established between the terminal and the 4G network. In the scenario of the N26 interface between the 4G core network MME and the 5G core network AMF, the PDU session and the evolved packet system (EPS) bearer have a mutual mapping relationship. When the 5G establishes the PDU session, the mapped EPS bearer is allocated, and in the case of the 4G establishing the PDN connection, the PDU session related parameters are allocated. For the scenario with the N26 interface, when the 4G network goes to the 5G network, the terminal needs to initiate a modification process to synchronize the PDU session related parameters of the network and the terminal, which increases the waste of air interface resources. SUMMARY

[0004] Embodiments of the present application aim to provide a mobility management method and device, equipment, a communication system, and a storage medium.

[0005] The technical solution of the present application is implemented as follows:

[0006] In a first aspect, a mobility management method is provided, applied to a terminal device, comprising:

[0007] sending a PDN connection request of a first communication network; wherein the PDN connection request comprises first PDU session information of establishing a PDU session on a second communication network by the terminal device;

[0008] receiving a PDN connection response corresponding to the PDN connection request in response to the PDN connection request, and establishing a PDN connection on the first communication network; wherein the PDN connection response comprises second PDU session information determined according to the first PDU session information;

[0009] storing the second PDU session information.

[0010] In a second aspect, a mobility management method applied to a network device is provided,

[0011] receiving a PDN connection request of a first communication network; wherein the PDN connection request comprises first PDU session information of establishing a PDU session on a second communication network;

[0012] determining second PDU session information according to the first PDU session information;

[0013] generating a PDN connection response according to the second PDU session information;

[0014] sending the PDN connection response, and establishing a PDN connection on the first communication network.

[0015] In a third aspect, a mobility management apparatus applied to a terminal device is provided. The mobility management apparatus can be a terminal device or a chip applied to a terminal device. In the present application, the mobility management apparatus can realize the functions of multiple units in a manner of software, hardware, or a combination of software and hardware, so that the apparatus can perform the mobility management method provided in any one of the first aspect. The effects of the technical solutions in the second aspect can refer to the corresponding technical solutions in the first aspect, which will not be repeated here.

[0016] Exemplarily, the apparatus comprises:

[0017] The first communication unit is configured to send a PDN connection request of a first communication network; wherein the PDN connection request comprises first PDU session information of establishing a PDU session on a second communication network by the terminal device;

[0018] The first communication unit is further configured to receive a PDN connection response corresponding to the PDN connection request in response to the PDN connection request, and establish a PDN connection on the first communication network; wherein the PDN connection response comprises second PDU session information determined according to the first PDU session information;

[0019] The storage unit is configured to store the second PDU session information.

[0020] In a fourth aspect, a mobility management apparatus is provided, which can be applied to a network device or a chip applied to a terminal device. In the present application, the mobility management apparatus can realize the functions of multiple units in a manner of software, hardware, or a combination of software and hardware, so that the apparatus can perform the mobility management method provided in any one of the first aspect. The effects of the technical solutions in the second aspect can refer to the corresponding technical solutions in the first aspect, which will not be repeated here.

[0021] In an example, the apparatus includes:

[0022] The second communication unit is configured to receive a PDN connection request of the first communication network, wherein the PDN connection request includes first PDU session information for establishing a PDU session on the second communication network.

[0023] The processing unit is configured to determine second PDU session information according to the first PDU session information, and generate a PDN connection response according to the second PDU session information.

[0024] The second communication unit is further configured to send the PDN connection response and establish a PDN connection on the first communication network.

[0025] In a fifth aspect, a mobility management device is provided, which can be applied to a terminal device or a network device. The mobility management device can be a terminal device or a chip applied to a terminal device. The mobility management device includes a processor and a memory configured to store a computer program capable of running on the processor,

[0026] The processor is configured to execute the steps of the foregoing method when running the computer program.

[0027] In a sixth aspect, a communication system is provided, which includes a terminal device and a network device.

[0028] The terminal device is configured to send a PDN connection request of the first communication network to the network device, wherein the PDN connection request includes first PDU session information for establishing a PDU session on the second communication network by the terminal device.

[0029] The network device is configured to: receive a PDN connection request of a first communication network; determine second PDU session information according to the first PDU session information; generate a PDN connection response according to the second PDU session information; and send the PDN connection response to the terminal device, and establish a PDN connection with the terminal device on the first communication network.

[0030] The terminal device is further configured to: save the second PDU session information.

[0031] In a seventh aspect, a computer readable storage medium is provided, and the computer readable storage medium stores a computer program. When the computer program is executed by a processor, the steps of the foregoing method are implemented. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 A system architecture of a communication system according to an embodiment of the present application Figure 1 ;

[0033] Figure 2 A system architecture of a communication system according to an embodiment of the present application Figure 2 ;

[0034] Figure 3 A first flowchart of a mobility management method according to an embodiment of the present application

[0035] Figure 4 A format of a 5GSM capability information element according to an embodiment of the present application

[0036] Figure 5 A second flowchart of a mobility management method according to an embodiment of the present application

[0037] Figure 6 A PDU session establishment process according to an embodiment of the present application

[0038] Figure 7 A PDN connection establishment process according to an embodiment of the present application

[0039] Figure 8 A network mode switching process according to an embodiment of the present application

[0040] Figure 9 A session modification process according to an embodiment of the present application

[0041] Figure 10 A structure of a mobility management apparatus according to an embodiment of the present application Figure 1 ;

[0042] Figure 11 A structure of a mobility management apparatus according to an embodiment of the present applicationFigure 2 ;

[0043] Figure 12 is a schematic structural diagram of a mobility management device provided by an embodiment of the present application;

[0044] Figure 13 is a schematic structural diagram of a chip of an embodiment of the present application;

[0045] Figure 14 is a schematic block diagram of a communication system provided by an embodiment of the present application. DETAILED DESCRIPTION

[0046] In order to enable a person skilled in the art to more fully understand the features and technical contents of the embodiments of the present application, the implementation of the embodiments of the present application will be described in detail below with reference to the accompanying drawings, which are only used for reference and are not used to limit the embodiments of the present application.

[0047] Figure 1 is a schematic system architecture of a communication system of an embodiment of the present application Figure 1 . As shown in Figure 1 , the communication system 100 can include a terminal device 110 and a network device 120. The network device 120 can communicate with the terminal device 110 through an air interface. The terminal device 110 and the network device 120 support multi-service transmission.

[0048] It should be understood that the embodiments of the present application are only exemplarily described with the communication system 100, but the embodiments of the present application are not limited thereto. That is, the technical solutions of the embodiments of the present application can be applied to various communication systems, such as: a Long Term Evolution (LTE) system, an LTE Time Division Duplex (TDD), a Universal Mobile Telecommunication System (UMTS), an Internet of Things (IoT) system, a Narrow Band Internet of Things (NB-IoT) system, an enhanced Machine-Type Communications (eMTC) system, a 5G communication system (also referred to as a New Radio (NR) communication system), or a future communication system, etc.

[0049] In Figure 1In the illustrated communication system 100, the network device 120 can be an access network device that communicates with the terminal device 110. The access network device can provide communication coverage for a specific geographic area and can communicate with the terminal device 110 (e.g., UE) located within the coverage area.

[0050] The network device 120 can be an evolved node B (eNB or eNodeB) in a long term evolution (LTE) system, or a next generation radio access network (NG RAN) device, or a base station (gNB) in a NR system, or a radio controller in a cloud radio access network (CRAN), or a relay station, an access point, a vehicle-mounted device, a wearable device, a hub, a switch, a bridge, a router, or a network device in a future evolved public land mobile network (PLMN), etc.

[0051] The terminal device 110 can be any terminal device, including but not limited to a terminal device that uses wired or wireless connection with the network device 120 or other terminal devices.

[0052] For example, the terminal device 110 can refer to an access terminal, a user equipment (UE), a subscriber unit, a subscriber station, a mobile station, a mobile, a remote station, a remote terminal, a mobile device, a user terminal, a terminal, a wireless communication device, a user agent, or a user device. The access terminal can be a cellular phone, a cordless phone, a session initiation protocol (SIP) phone, an IoT device, a satellite handset, a wireless local loop (WLL) station, a personal digital assistant (PDA), a handheld device with wireless communication function, a computing device, or other processing device connected to a wireless modem, a vehicle-mounted device, a wearable device, a terminal device in a 5G network, or a terminal device in a future evolved network, etc.

[0053] The terminal device 110 can be used for device to device (D2D) communication.

[0054] The wireless communication system 100 can further include a core network device 130 in communication with the base station, which can be a 5G core network (5GC) device, e.g., an Access and Mobility Management Function (AMF), e.g., an Authentication Server Function (AUSF), e.g., a User Plane Function (UPF), e.g., a Session Management Function (SMF). Alternatively, the core network device 130 can also be an Evolved Packet Core (EPC) device of an LTE network, e.g., a Session Management Function + Core Packet Gateway (SMF + PGW-C) device. It should be understood that the SMF + PGW-C can implement the functions of both the SMF and the PGW-C. During the evolution of the network, the core network device can also be referred to as other names, or new network entities can be formed by dividing the functions of the core network, which is not limited by the embodiments of the present application.

[0055] The functional units in the communication system 100 can also communicate with each other through a next generation (NG) interface. For example, the terminal device establishes an air interface connection with the access network device through the NR interface, which is used to transmit user plane data and control plane signaling; the terminal device can establish a control plane signaling connection with the AMF through the NG interface 1 (N1 for short); the access network device, e.g., a next generation radio access base station (gNB), can establish a user plane data connection with the UPF through the NG interface 3 (N3 for short); the access network device can establish a control plane signaling connection with the AMF through the NG interface 2 (N2 for short); the UPF can establish a control plane signaling connection with the SMF through the NG interface 4 (N4 for short); the UPF can interact with the data network to transmit user plane data through the NG interface 6 (N6 for short); the AMF can establish a control plane signaling connection with the SMF through the NG interface 11 (N11 for short); the SMF can establish a control plane signaling connection with the PCF through the NG interface 7 (N7 for short).

[0056] It should be noted that, Figure 1The system to which the embodiments of the present application apply is exemplarily shown, and of course, the method shown in the embodiments of the present application can also be applied to other systems. In addition, the terms "system" and "network" are often used interchangeably in this document. The term "and / or" in this document is only used to describe the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B can represent the following three cases: A exists alone, A and B exist together, and B exists alone. In addition, the character " / " in this document generally represents an "or" relationship between the front and rear associated objects. It should also be understood that the "indication" mentioned in the embodiments of the present application can be direct indication or indirect indication, and can also mean having an associated relationship. For example, A indicates B can mean that B can be obtained by A directly, or A indicates C and B can be obtained by C indirectly, or A and B have an associated relationship. It should also be understood that the "corresponding" mentioned in the embodiments of the present application can mean that there is a direct or indirect corresponding relationship between the two, or there can be an associated relationship between the two, or it can mean the relationship of indication and being indicated, configuration and being configured, etc. It should also be understood that the "predefined" or "predefined rule" mentioned in the embodiments of the present application can be realized by pre-saving the corresponding code, table or other means that can be used to indicate the relevant information in the device (for example, including terminal device and network device), and the specific implementation manner of the present application is not limited. For example, the predefined can mean the definition in the protocol. It should also be understood that the "protocol" in the embodiments of the present application can mean the standard protocol in the communication field, which can include the LTE protocol, the NR protocol and the related protocol applied to the future communication system, and the present application is not limited thereto.

[0057] Figure 2 Exemplarily, one base station, one core network device and two terminal devices are shown, optionally, the wireless communication system 100 can include a plurality of base station devices and each base station can include other number of terminal devices within the coverage range, and the embodiments of the present application are not limited thereto.

[0058] From the current networking situation, 4G network and 5G network are a long-term coexistence process. In order to realize the smooth transition of business, the N26 interface is added between the 4G core network mobility management entity (MME) and the 5G core network access and mobility management function (AMF) to realize the information interaction between 5GC and EPC. Whether the mobile network operator supports the N26 interface in the 4G network and the 5G network is optional. After the N26 interface is turned on, the terminal can exchange the mobility management (MM) and service session (SM) states between the source network and the target network when the terminal performs 4G and 5G interoperation. Through the N26 interface, the terminal switching between 4G and 5G and the registration information of the terminal can also be supported.

[0059] Figure 2 A system architecture diagram of a communication system according to an embodiment of the present application Figure 3 The core network device 130 includes a 5G core network (5GC) and a 4G core network (EPC), and the access network device includes a base station (gNB) in the NR system and a base station (eNB) in the LTE system. The 5GC at least includes an AMF device, mainly responsible for registration management, connection management and mobility management of the terminal. The EPC at least includes an MME device, mainly responsible for authentication, authorization, mobility management and session management of the terminal. The N26 interface is added between the AMF and the MME to realize the information interaction between the 5GC and the EPC.

[0060] In the scenario of the N26 interface between the 4G core network MME and the 5G core network AMF, the PDU session and the EPS bearer have a mutual mapping relationship. When the 5G establishes the PDU session, the corresponding EPS bearer will be allocated, and in the case of establishing the PDN connection in the 4G, the corresponding PDU session related parameters will be allocated.

[0061] Protocol data network (PDN) connection: a combination of a group of EPS bearers established on the terminal in the 4G network, the EPS bearers have the same IP address and access point name (APN), and the EPS bearer refers to a data transmission channel in the 4G network. In the terminal and the network side, an IP address and an APN are used to identify a PDN connection.

[0062] PDU session: refers to a process of communication between a user equipment (UE) and a data network (DN). After the PDU session is established, a data transmission channel between the UE and the DN is established. In a 5G network, a combination of a set of QoS flows established on a terminal, the QoS flows having the same IP address and data network name (DNN). The QoS flow refers to a data transmission channel in the 5G network. On the terminal and the network side, the PDU session is identified by the IP address and the DNN.

[0063] For the scenario with the N26 interface, when the 4G network is switched to the 5G network, the terminal needs to initiate a modification process to synchronize the PDU session related parameters of the network and the terminal, which increases the waste of air interface resources.

[0064] To facilitate understanding of the technical solutions of the embodiments of the present application, the related technologies of the embodiments of the present application are described below. The following related technologies can be combined with the technical solutions of the embodiments of the present application in any manner, and all of them belong to the protection scope of the embodiments of the present application.

[0065] Figure 3 A first flow diagram of the mobility management method in the embodiments of the present application is shown in FIG. 1, which is applied to a terminal device and can specifically include the following steps. Figure 4

[0066] Step 301: sending a PDN connection request of a first communication network; wherein the PDN connection request includes first PDU session information of the terminal device for establishing a PDU session on a second communication network;

[0067] Here, the first PDU session information can be understood as the PDU session information sent by the terminal device to the network device, which is used for PDU session negotiation with the network device to realize PDU session information sharing. The network device generates and sends the second PDU session information to the terminal device according to the first PDU session information, and the second PDU session information contains all the information of the PDU session establishment.

[0068] In some optional embodiments, the first PDU session information includes a first information element, which can be an information element sent by the terminal to the network device when initiating the modification process. For example, the first information element includes one of the following: the maximum number of supported packet filters, PDU session permanent online request, integrity protection maximum data rate, and PDU session management capability.

[0069] ​The integrity protection maximum data rate indicates a maximum data rate that the terminal device can support for uplink integrity protection. The terminal device requests a "PDU permanent online session" SMF to participate in determining whether a "PDU permanent online session" needs to be established. The number of data packet filters indicates the number of data packet filters supported by the protocol description signaling QoS rule. The PDU session management capability is used to indicate the UE capability related to PDU session management.

[0070] Exemplarily, Figure 4 A format diagram of the 5GSM capability information element in the embodiments of the present application is shown in FIG. 3. As shown in FIG. 3, the 5GSM capability information element includes 16 bytes. Byte 1 is a 5GSM capability information element flag bit. Byte 2 is the length of the 5GSM capability content. The lower five bits of byte 3 are the 5GSM capability content, and the upper three bits are reserved bits. Bytes 4-15 are reserved bits. Figure 5

[0071] In some optional embodiments, the first information element is a newly added information element in the first connection request; or the first information element is a newly added information element in the protocol configuration option (PCO) of the first connection request.

[0072] Step 302: receiving a PDN connection response corresponding to the PDN connection request, and establishing a PDN connection on the first communication network; wherein the PDN connection response includes second PDU session information determined according to the first PDU session information;

[0073] In some optional embodiments, the second PDU session information includes a second information element generated according to the first information element; and / or, an acknowledgement of the first information element.

[0074] Exemplarily, when the network device determines that the first information element is consistent with the PDU session reference information saved on the network side, the network device returns an acknowledgement; or directly issues the first information element to the terminal device as the second information element; or when the network device determines that the first information element is inconsistent with the PDU session reference information saved on the network side, the network device generates a second information element by modifying the first information element according to the saved PDU session reference information and issues the second information element to the terminal device; or, a part of the first information element returns an acknowledgement, and another part of the first information element returns an information element. The information sharing between the network and the terminal device is realized.

[0075] The second information element is a newly added information element in the first connection response; or the second information element is a newly added information element in the protocol configuration option of the first connection response.​

[0076] In some optional embodiments, the first PDU session information further includes a third information element, which includes at least one of the following: PDU session identifier, requested QoS rule, and requested QoS flow description.

[0077] The second PDU session information also includes a fourth information element generated based on the third information element. For example, the fourth information element includes at least one of the following: network slice parameters, QoS rules, maximum bit rate of session aggregation, PDU session address lifetime, QoS flow description, QoS rules with a length of two octets, and QoS flow description with a length of two octets.

[0078] Here, the third information element can be understood as a request message sent by the terminal to the network, requesting the network device to send the fourth information element.

[0079] Step 303: Save the second PDU session information.

[0080] In some optional embodiments, when switching from the first communication network to the second communication network, a PDU session is established on the second communication network based on the second PDU session information.

[0081] Using the above technical solution, when the terminal device activates the PDN connection, it can share PDU session information with the network through the PDN connection request and PDN connection response. When the terminal device switches from the first communication network to the second communication network, it can directly use the saved second PDU session information to establish a PDU session without having to perform the PDU session modification process, thus saving air interface resources.

[0082] like Figure 4 As shown, this method is applied to network devices and may specifically include:

[0083] Step 501: Receive a PDN connection request from the first communication network; wherein the PDN connection request includes first PDU session information for establishing a PDU session on the second communication network;

[0084] Here, the first PDU session information can be understood as the PDU session information sent by the terminal device to the network device, used to negotiate the PDU session and achieve PDU session information sharing. The network device generates and sends the second PDU session information to the terminal device based on the first PDU session information. The second PDU session information contains all the information for establishing the PDU session.

[0085] In some optional embodiments, the first PDU session information includes a first information element, which can be an information element sent to the network device when the terminal initiates a modification process. For example, the first information element includes one of the following: the maximum number of supported packet filters, a PDU session always-on request, a maximum data rate for integrity protection, and PDU session management capabilities.

[0086] The maximum data rate for integrity protection indicates the maximum data rate that the terminal device can support for uplink integrity protection. The terminal will request a "PDU Persistent Online Session," and the SMF will participate in deciding whether to establish such a session. The number of packet filters indicates the number of packet filters supported by the signaling notification QoS rules described in the protocol. PDU session management capabilities indicate the UE capabilities related to PDU session management.

[0087] For example, Figure 4 This is a schematic diagram of the format of the 5GSM capability information element in the embodiments of this application, such as... Figure 6 As shown, it includes 16 bytes. Byte 1 is the 5GSM capability information element flag bit, byte 2 is the 5GSM capability content length, the lower five bits of byte 3 are the 5GSM capability content, the higher three bits are reserved bits, and bytes 4-15 are reserved bits.

[0088] In some optional embodiments, the first information element is a newly added information element in the first connection request; or, the first information element is a newly added information element of the Protocol Configuration Option (PCO) in the first connection request.

[0089] Step 502: Determine the second PDU session information based on the first PDU session information;

[0090] In some optional embodiments, the second PDU session information generated based on the first PDU session information includes: obtaining PDU session reference information of the second communication network; and generating the second PDU session information based on the first PDU session information and the PDU session reference information.

[0091] Here, the PDU session reference information is PDU session related information that the network device of the first communication network obtains in advance, for example: PDU session ID, session type (IPv4, IPv6, IPv4v6, Ethenet, Unstructured), uplink and downlink rate, charging ID, roaming state information, IP information of the terminal, PCF information, Qos information, tunnel information, destination address, SMF identifier, slice information (if supported), default DRB information, data network name, AMF information, user location information, session management information, UPF ID, online charging identifier, offline charging identifier, and other related information.

[0092] In some optional embodiments, the obtaining the PDU session reference information of the second communication network comprises: obtaining the PDU session reference information sent by the network device corresponding to the second communication network through a connection interface between the network device corresponding to the second communication network. For example, the connection interface can be an N26 interface between a 4G core network MME and a 5G core network AMF, and the 4G core network MME obtains the PDU session reference information sent by the 5G core network AMF through the N26 interface.

[0093] In some optional embodiments, the obtaining the PDU session reference information of the second communication network comprises: obtaining the subscription information of the second communication network sent by the operator device; and obtaining the PDU session reference information from the subscription information of the second communication network.

[0094] That is, the PDU session reference information can be obtained from the network device corresponding to the second communication network, or from the subscription information of the second communication network sent by the operator device.

[0095] In some optional embodiments, the second PDU session information comprises a second information element generated according to the first information element; and / or, an acknowledgement response of the first information element.

[0096] For example, when the network device determines that the first information element is consistent with the PDU session reference information saved on the network side, an acknowledgement response is returned; or the first information element is directly sent to the terminal device as the second information element; or when the network device determines that the first information element is inconsistent with the PDU session reference information saved on the network side, the first information element is modified to generate the second information element according to the saved PDU session reference information and sent to the terminal device; or part of the information elements in the first information element returns an acknowledgement response, and the other part of the information elements returns an information element. The information sharing between the network and the terminal is realized.

[0097] The second information element is a newly added information element in the first connection response, or the second information element is a newly added information element in a protocol configuration option of the first connection response.

[0098] In some optional embodiments, the first PDU session information further includes a third information element, and the third information element includes at least one of a PDU session identifier, a requested QoS rule, and a requested QoS flow description.

[0099] The second PDU session information further includes a fourth information element generated according to the third information element, and the fourth information element includes at least one of a network slice parameter, a QoS rule, a session aggregate maximum bit rate, a PDU session address lifetime, a QoS flow description, a QoS rule with a length of two octets, and a QoS flow description with a length of two octets.

[0100] Here, the third information element can be understood as a request message sent by the terminal to the network, requesting the network device to issue the fourth information element.

[0101] Step 503: generating a PDN connection response according to the second PDU session information.

[0102] In some optional embodiments, an activate default EPS bearer context request is generated according to the PDN connection request, and a PDN connection response is generated according to the second PDU session information and the activate default EPS bearer context request. The network issues the activate default EPS bearer context request to establish a default EPS bearer context between the terminal and the network.

[0103] Step 504: sending the PDN connection response to establish a PDN connection on the first communication network.

[0104] In the embodiments of the present application, when the terminal device activates the PDN connection, the terminal and the network realize PDU session information sharing through the PDN connection request and the PDN connection response. When the terminal device switches from the first communication network to the second communication network, the second PDU session information is directly used to establish a PDU session, and the modification process of the PDU session is not needed, thereby saving air interface resources. The first communication network (for example, a 4G network) and the second communication network (for example, a 5G network) are different network systems, and the switching (Handover) / reselecting (Reselect) / redirecting (Redirect) and the like of the terminal device from the first communication network to the second communication network can include a cross-system process.

[0105] The application scenarios of the mobility management method of the embodiments of the present application are exemplarily described below.

[0106] Scenario one: PDU session establishment saves the corresponding mapping EPS bearer, carries the EPS bearer context in the process of PDU session establishment, and the terminal saves the corresponding EPS bearer context. As shown in Figure 7 , the PDU session establishment process specifically includes:

[0107] 1. The mobility management (MM) unit of the terminal device generates a registration request (REGISTRATION REQUEST) and sends it to the 5G network device (NET);

[0108] 2. The MM receives a registration acceptance (REGISTRATION ACCEPT) message;

[0109] 3. The MM sends a registration completion (REGISTRATION COMPLETE) message to the NET1;

[0110] 4. The session management (SM) unit of the terminal device generates a PDU session establishment request (SM_PDU_SESSION_EST_REQ) and sends it to the MM;

[0111] 5. The MM sends an uplink non-access layer transmission (UL NAS TRANSPORT) message including the PDU_SESSION_REQ to the NET;

[0112] 6. The PDU session establishment is successful, and the NET sends a downlink non-access layer transmission (DL NAS TRANSPORT) message including a PDU session establishment acceptance message (PDU_SESSION_ACCEPT) to the MM, wherein the PDU_SESSION_ACCEPT includes: mapped EPS bearer contexts (Mapped EPS bearer contexts);

[0113] 7. The MM sends a PDU session establishment acceptance indication (SM_PDU_SESSION_ACCEPT_IND) including the Mapped EPS bearer contexts to the SM, and the SM saves the Mapped EPS bearer contexts, which are used to establish a PDN connection according to the Mapped EPS bearer contexts when switching from the 5G network to the 4G network.

[0114] Scenario two: 4G PDN establishment saves the corresponding PDU session information, and the terminal device activates the 4G PDN connection, requests the PDU session information and saves it. As shown in Figure 8 , the PDN connection establishment process specifically includes:

[0115] 1. The SM generates a PDN CONNECTIVITY REQUEST and sends it to the MM, the PDN CONNECTIVITY REQUEST including first PDU session information in the terminal-to-network direction;

[0116] The first PDU session information includes:

[0117] - 001AH (PDU session ID), i.e., PDU session identification;

[0118] - 0023H (QoS rules with the length of two octets support indicator), i.e., request for QoS rules, specifically, a support indicator for QoS rules with a length of two octets;

[0119] - 0024H (QoS flow descriptions with the length of two octets support indicator), i.e., request for QoS flow descriptions, specifically, a support indicator for QoS flow descriptions with a length of two octets;

[0120] - Maximum number of supported packet filters, i.e., maximum number of supported data packet filters;

[0121] - Always-on PDU session requested, i.e., PDU session permanent online request;

[0122] - Integrity protection maximum data rate, i.e., integrity protection maximum data rate;

[0123] - 5GSM capability, i.e., PDU session management capability.

[0124] 2. The MM sends an ATTACH REQUEST including the PDN CONNECTIVITY REQUEST to a 4G network device (NET); the purpose of the PDN CONNECTIVITY REQUEST is to establish a default bearer between the terminal and the P-GW of the 4G network, and the default bearer remains connected until the terminal detaches from the LTE network.

[0125] 3. The NET sends an Attach Accept (ATTACH ACCEPT) including an Activate Default EPS Bearer Context Request (ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST); the Activate Default EPS Bearer Context Request includes second PDU session information in network-to-terminal direction;

[0126] wherein the second PDU session information includes:

[0127] -001BH (S-NSSAI), i.e. Single Network Slice Selection Assistance Information (S-NSSAI);

[0128] -001CH (QoS rules), i.e. QoS rules;

[0129] -001DH (Session-AMBR), i.e. session-aggregate maximum bit rate (Session-AMBR)

[0130] -001EH (PDU session address lifetime), i.e. PDU session address lifetime;

[0131] -001FH (QoS flow descriptions), i.e. QoS flow descriptions;

[0132] -0023H (QoS rules with the length of two octets), i.e. QoS rules with the length of two octets;

[0133] -0024H (QoS flow descriptions with the length of two octets), i.e. QoS flow descriptions with the length of two octets;

[0134] - Maximum number of supported packet filters, i.e. maximum number of supported packet filters,

[0135] - Always-on PDU session requested, i.e. PDU session permanent online request;

[0136] - Integrity protection maximum data rate, i.e. the maximum data rate for integrity protection;

[0137] - 5GSM capability, i.e. PDU session management capability.

[0138] 4. The MM sends an ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST to the SM;

[0139] 5. The SM saves the second PDU session information;

[0140] 6. The SM sends an ACTIVATE DEFAULT EPS BEARER CONTEXT ACCEPT to the MM;

[0141] 7. The MM sends an ATTACH COMPLETE including the ACTIVATE DEFAULT EPS BEARER CONTEXT ACCEPT to the NET.

[0142] Scenario three: 4G network to 5G network, 4G PDN establishment saves the corresponding PDU session information, when performing a cross-mode process such as handover, reselection, redirection, etc. from 4G to 5G, a PDN session is directly established according to the saved PDU session information, without the need to initiate a PDU session modification process, saving air interface resources. As shown in FIG. 3, 4G network to 5G network specifically includes: Figure 9

[0143] 1. When the terminal device activates a 4G PDN connection, request PDU session information and save.

[0144] 2. The access layer (Access Stratum, AS) of the terminal device generates a handover instruction (AS_NAS_IRAT_CHANGE_IND (4->5)) and sends it to the MM;

[0145] 3. The MM sends a PDP context query request (MM_SM_PDP_CONTEXT_QUREY_REQ) to the SM;

[0146] 4. The SM sends a PDP context query response (MM_SM_PDP_CONTEXT_QUREY_CNF) including the allowed PDU session status (Allowed PDU session status) to the MM;

[0147] ​4. The MM sends a registration request (REGISTRATION REQUEST) including allowed PDU session status to a 5G network device (NET);

[0148] 5. The NET sends a registration accept (REGISTRATION ACCEPT) including PDU session status to the MM;

[0149] 6. The MM sends a PDU session message (MM_SM_PDU_SESSION_NET_IND) including PDU session status to the SM, and the SM does not need to initiate a modification procedure.

[0150] As shown in Figure 9 the prior art, when the terminal currently normally camps on a 4G network, if a PDN connection is a newly activated 4G PDN connection and PDU session information is saved, when the terminal switches from the newly activated 4G PDN connection to 5G, the terminal needs to initiate a PDU session information modification procedure to obtain all PDU session information corresponding to the newly activated PDN connection. As shown in Figure 10 the prior art, the SM needs to initiate a modification procedure (mobile originate) to obtain information such as a maximum number of supported packet filters, a PDU session permanent online request, a maximum data rate for integrity protection, and 5G mobility management capabilities.

[0151] The embodiments of the present application also provide a mobility management device applied to a terminal device, Figure 1 is a structural composition of the mobility management device provided by the embodiments of the present application Figure 10 As shown in Figure 11 the mobility management device 1000 includes:

[0152] The first communication unit 1001 is configured to send a PDN connection request of a first communication network, wherein the PDN connection request includes first PDU session information of the terminal device for establishing a PDU session on a second communication network;

[0153] The first communication unit 1001 is further configured to receive a PDN connection response corresponding to the PDN connection request, and establish a PDN connection on the first communication network, wherein the PDN connection response includes second PDU session information determined according to the first PDU session information;

[0154] The storage unit 1002 is configured to save the second PDU session information.

[0155] In some optional embodiments, the first PDU session information includes a first information element, and the first information element includes one of the following: a maximum number of supported data packet filters, a PDU session permanent online request, an integrity protection maximum data rate, and a PDU session management capability.

[0156] In some optional embodiments, the first information element is a newly added information element in the first connection request; or the first information element is a newly added information element in a protocol configuration option of the first connection request.

[0157] In some optional embodiments, the second PDU session information includes a second information element generated according to the first information element; and / or an acknowledgement response of the first information element.

[0158] In some optional embodiments, the second information element is a newly added information element in the first connection response; or the second information element is a newly added information element in a protocol configuration option of the first connection response.

[0159] In some optional embodiments, the first PDU session information further includes a third information element, and the third information element includes at least one of the following: a PDU session identifier, a requested QoS rule, and a requested QoS flow description; and the second PDU session information further includes a fourth information element generated according to the third information element, and the fourth information element includes at least one of the following: a network slice parameter, a QoS rule, a session aggregate maximum bit rate, a PDU session address lifetime, a QoS flow description, a QoS rule with a length of two octets, and a QoS flow description with a length of two octets.

[0160] In some optional embodiments, the first communication unit 1001 is further configured to: when switching from the first communication network to the second communication network, establish a PDU session on the second communication network according to the second PDU session information.

[0161] Embodiments of the present application also provide a mobility management apparatus, applied to a network device, Figure 1 Figure 1 shows a structure of a mobility management apparatus provided by an embodiment of the present application Figure 11 As shown in Figure 1, the mobility management apparatus 1100 includes: Figure 12 The second communication unit 1101 is configured to: receive a PDN connection request of a first communication network; wherein the PDN connection request includes first PDU session information for establishing a PDU session on a second communication network;

[0162]

[0163] ​The processing unit 1102 is configured to: determine second PDU session information according to the first PDU session information; and generate a PDN connection response according to the second PDU session information.

[0164] The second communication unit 1101 is further configured to: send the PDN connection response, and establish a PDN connection on the first communication network.

[0165] The processing unit 1102 is configured to: obtain PDU session reference information of the second communication network.

[0166] The second PDU session information is generated according to the first PDU session information and the PDU session reference information.

[0167] In some optional embodiments, the second communication unit 1101 is further configured to: obtain the PDU session reference information sent by a network device corresponding to the second communication network through a connection interface between the network device and the second communication network; or, obtain subscription information of the second communication network sent by an operator device; and obtain the PDU session reference information from the subscription information of the second communication network.

[0168] In some optional embodiments, the first PDU session information includes a first information element, and the first information element includes one of the following: a maximum number of supported data packet filters, a PDU session permanent online request, an integrity protection maximum data rate, and a PDU session management capability.

[0169] In some optional embodiments, the first information element is a newly added information element in the first connection request; or, the first information element is a newly added information element in a protocol configuration option of the first connection request.

[0170] In some optional embodiments, the second PDU session information includes a second information element generated according to the first information element; and / or, an acknowledgement response of the first information element.

[0171] In some optional embodiments, the second information element is a newly added information element in the first connection response; or, the second information element is a newly added information element in a protocol configuration option of the first connection response.

[0172] In some optional embodiments, the first PDU session information further includes a third information element, and the third information element includes at least one of the following: a PDU session identifier, a requested QoS rule, and a requested QoS flow description; and the second PDU session information further includes a fourth information element generated according to the third information element, and the fourth information element includes at least one of the following: a network slice parameter, a QoS rule, a session aggregate maximum bit rate, a PDU session address lifetime, a QoS flow description, a QoS rule with a two-octet length, and a QoS flow description with a two-octet length.

[0173] Figure 12 Figure 1 is a schematic structural diagram of a mobility management device provided by an embodiment of the present application. The mobility management device can be a terminal device or a network device. Figure 12 The mobility management device 1200 shown in the figure includes a processor 1210, which can invoke and run a computer program from a memory to implement the method in the embodiments of the present application.

[0174] Optionally, as shown in the figure, the mobility management device 1200 can further include a memory 1220. The processor 1210 can invoke and run a computer program from the memory 1220 to implement the method in the embodiments of the present application. Figure 12

[0175] The memory 1220 can be a separate device independent of the processor 1210, or can be integrated in the processor 1210.

[0176] Optionally, as shown in the figure, the mobility management device 1200 can further include a transceiver 1230, and the processor 1210 can control the transceiver 1230 to communicate with other devices, specifically, to send information or data to other devices or receive information or data sent by other devices. Figure 13

[0177] The transceiver 1230 can include a transmitter and a receiver. The transceiver 1230 can further include an antenna, and the number of antennas can be one or more.

[0178] Optionally, the mobility management device 1200 can be a network device of the embodiments of the present application, and the mobility management device 1200 can implement the corresponding processes in the various methods of the embodiments of the present application implemented by the network device. For the sake of brevity, details are not repeated here.

[0179] ​​Optionally, the mobility management device 1200 can be a mobile terminal / terminal device of the embodiments of the present application, and the mobility management device 1200 can implement the corresponding processes implemented by the mobile terminal / terminal device in the various methods of the embodiments of the present application. For brevity, details are not repeated here.

[0180] The mobility management device can be a chip, Figure 13 is a schematic structural diagram of a chip of the embodiments of the present application. Figure 13 The chip 1300 shown includes a processor 1310, which can call and run a computer program from a memory to implement the method in the embodiments of the present application.

[0181] Optionally, as Figure 14 The chip 1300 shown can also include a memory 1320. The processor 1310 can call and run a computer program from the memory 1320 to implement the method in the embodiments of the present application.

[0182] The memory 1320 can be a separate device independent of the processor 1310, or can be integrated in the processor 1310.

[0183] Optionally, the chip 1300 can also include an input interface 1330. The processor 1310 can control the input interface 1330 to communicate with other devices or chips, and specifically, can obtain information or data sent by other devices or chips.

[0184] Optionally, the chip 1300 can also include an output interface 1340. The processor 1310 can control the output interface 1340 to communicate with other devices or chips, and specifically, can output information or data to other devices or chips.

[0185] Optionally, the chip can be applied to the network device in the embodiments of the present application, and the chip can implement the corresponding processes implemented by the network device in the various methods of the embodiments of the present application. For brevity, details are not repeated here.

[0186] Optionally, the chip can be applied to the mobile terminal / terminal device in the embodiments of the present application, and the chip can implement the corresponding processes implemented by the mobile terminal / terminal device in the various methods of the embodiments of the present application. For brevity, details are not repeated here.

[0187] It should be understood that the chip mentioned in the embodiments of the present application can also be referred to as a system-level chip, a system chip, a chip system, or a system-on-chip chip, etc.

[0188] Figure 14 is a schematic block diagram of a communication system provided by the embodiments of the present application. As ​As shown, the communication system 1400 includes a terminal device 1410 and a network device 1420.

[0189] The terminal device 1410 can be configured to implement the corresponding functions of the terminal device in the above method, and the network device 1420 can be configured to implement the corresponding functions of the network device in the above method. For brevity, details are not repeated here.

[0190] It should be understood that the processor of the embodiments of the present application can be an integrated circuit chip having a signal processing capability. In the implementation process, each step of the above method embodiments can be completed by integrated logic circuits or instructions in the form of software in the processor. The processor described above can be a general processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic device, a discrete hardware component. Each method, step and logic block disclosed in the embodiments of the present application can be implemented or executed. The general processor can be a microprocessor or the processor can be any conventional processor. The steps of the method disclosed in conjunction with the embodiments of the present application can be directly embodied as a hardware code processor for execution, or a combination of hardware and software modules in the code processor for execution. The software module can be located in a random access memory, a flash memory, a read only memory, a programmable read only memory or an electrically erasable programmable memory, a register or other mature storage medium in the art. The storage medium is located in the memory, and the processor reads the information in the memory, and combines the hardware to complete the steps of the above method.

[0191] It is to be understood that the memory in the embodiments of the present application can be a volatile memory or a nonvolatile memory, or can include both volatile and nonvolatile memory. Among them, the nonvolatile memory can be a read-only memory (Read-Only Memory, ROM), a programmable read-only memory (Programmable ROM, PROM), an erasable programmable read-only memory (Erasable PROM, EPROM), an electrically erasable programmable read-only memory (Electrically EPROM, EEPROM) or a flash memory. The volatile memory can be a random access memory (Random Access Memory, RAM) used as an external cache. By way of example, but not limitation, many forms of RAM are available, such as static random access memory (Static RAM, SRAM), dynamic random access memory (Dynamic RAM, DRAM), synchronous dynamic random access memory (Synchronous DRAM, SDRAM), double data rate synchronous dynamic random access memory (Double Data Rate SDRAM, DDR SDRAM), enhanced synchronous dynamic random access memory (Enhanced SDRAM, ESDRAM), synchronous link dynamic random access memory (Synchlink DRAM, SLDRAM) and direct memory bus random access memory (Direct Rambus RAM, DR RAM). It should be noted that the memory of the system and method described herein is intended to include, but not limited to, these and any other suitable types of memory.

[0192] It should be understood that the above-mentioned memory is exemplary but not limiting, for example, the memory in the embodiments of the present application can also be static random access memory (static RAM, SRAM), dynamic random access memory (dynamic RAM, DRAM), synchronous dynamic random access memory (synchronous DRAM, SDRAM), double data rate synchronous dynamic random access memory (double data rate SDRAM, DDR SDRAM), enhanced synchronous dynamic random access memory (enhanced SDRAM, ESDRAM), synchronous link dynamic random access memory (synch link DRAM, SLDRAM) and direct memory bus random access memory (Direct Rambus RAM, DR RAM) and the like. That is, the memory in the embodiments of the present application is intended to include, but not limited to, these and any other suitable types of memory.

[0193] The embodiment of the present application further provides a computer readable storage medium for storing the computer program.

[0194] Optionally, the computer readable storage medium can be applied to the network device in the embodiment of the present application, and the computer program makes the computer execute the corresponding process realized by the network device in the various methods of the embodiment of the present application, which will not be repeated here for the sake of brevity.

[0195] Optionally, the computer readable storage medium can be applied to the mobile terminal / terminal device in the embodiment of the present application, and the computer program makes the computer execute the corresponding process realized by the mobile terminal / terminal device in the various methods of the embodiment of the present application, which will not be repeated here for the sake of brevity.

[0196] The embodiment of the present application further provides a computer program product comprising computer program instructions.

[0197] Optionally, the computer program product can be applied to the network device in the embodiment of the present application, and the computer program instructions make the computer execute the corresponding process realized by the network device in the various methods of the embodiment of the present application, which will not be repeated here for the sake of brevity.

[0198] Optionally, the computer program product can be applied to the mobile terminal / terminal device in the embodiment of the present application, and the computer program instructions make the computer execute the corresponding process realized by the mobile terminal / terminal device in the various methods of the embodiment of the present application, which will not be repeated here for the sake of brevity.

[0199] The embodiment of the present application further provides a computer program.

[0200] Optionally, the computer program can be applied to the network device in the embodiment of the present application, and when the computer program runs on the computer, makes the computer execute the corresponding process realized by the network device in the various methods of the embodiment of the present application, which will not be repeated here for the sake of brevity.

[0201] Optionally, the computer program can be applied to the mobile terminal / terminal device in the embodiment of the present application, and when the computer program runs on the computer, makes the computer execute the corresponding process realized by the mobile terminal / terminal device in the various methods of the embodiment of the present application, which will not be repeated here for the sake of brevity.

[0202] Those skilled in the art can clearly understand that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be realized by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0203] Those skilled in the art can clearly understand that, for the convenience and brevity of the description, the specific working processes of the above-described system, device and unit can refer to the corresponding processes in the foregoing method embodiments, which will not be repeated here.

[0204] In several embodiments provided in the present application, it should be understood that the disclosed system, device and method can be implemented in other ways. For example, the above-described device embodiments are merely schematic, for example, the division of the units is only a logical function division, and actual implementation can have another division manner, for example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units shown or discussed can be indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0205] The units described as separate components can or can not be physically separated, and the components shown as units can or can not be physical units, that is, they can be located in one place, or can be distributed on multiple network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the embodiment.

[0206] In addition, each functional unit in each embodiment of the present application can be integrated into a processing unit, or each unit can exist physically independently, or two or more units can be integrated into one unit.

[0207] If the functions are implemented in the form of software function units and sold or used as independent products, they can be stored in a computer readable storage medium. Based on this understanding, the technical solutions of the present application or the parts of the technical solutions that essentially contribute to the prior art or the parts of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present application. The aforementioned storage medium includes a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, and various media that can store program codes.

[0208] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A mobility management method applied to a terminal device, characterized in that, The method includes: Send a PDN connection request to the first communication network; wherein, the PDN connection request includes first PDU session information for the terminal device to establish a PDU session on the second communication network; The system receives a PDN connection response corresponding to the PDN connection request and establishes a PDN connection on the first communication network. The PDN connection response includes second PDU session information determined based on the first PDU session information. The second PDU session information includes a fourth information element, which includes at least one of the following: network slice parameters, QoS rules, maximum bit rate of session aggregation, PDU session address lifetime, QoS flow description, QoS rules with a length of two octets, and QoS flow description with a length of two octets. Save the second PDU session information.

2. The method according to claim 1, characterized in that, The first PDU session information includes a first information element, which includes one of the following: the maximum number of supported packet filters, the PDU session always-on request, the maximum data rate for integrity protection, and PDU session management capabilities.

3. The method according to claim 2, characterized in that, The first information element is a newly added information element in the PDN connection request of the first communication network; Alternatively, the first information element may be a newly added information element in the protocol configuration options of the PDN connection request of the first communication network.

4. The method according to claim 2, characterized in that, The second PDU session information includes a second information element generated based on the first information element; and / or, an acknowledgment response to the first information element.

5. The method according to any one of claims 2-4, characterized in that, The first PDU session information also includes a third information element, which includes at least one of the following: PDU session identifier, request QoS rule, request QoS flow description; The fourth information element included in the second PDU session information is generated based on the third information element; The second PDU session information also includes: the maximum number of supported packet filters, PDU session persistent online requests, maximum data rate for integrity protection, and PDU session management capabilities.

6. The method according to claim 1, characterized in that, The method further includes: When switching from the first communication network to the second communication network, a PDU session is established on the second communication network based on the second PDU session information.

7. A mobility management method applied to network devices, characterized in that, Receive a PDN connection request from a first communication network; wherein, the PDN connection request includes first PDU session information for establishing a PDU session on a second communication network; The second PDU session information is determined based on the first PDU session information; the second PDU session information includes a fourth information element, which includes at least one of the following: network slice parameters, QoS rules, maximum bit rate of session aggregation, PDU session address lifetime, QoS flow description, QoS rules with a length of two octets, and QoS flow description with a length of two octets. Generate a PDN connection response based on the second PDU session information; Send the PDN connection response to establish a PDN connection on the first communication network.

8. The method according to claim 7, characterized in that, Determining the second PDU session information based on the first PDU session information includes: Obtain PDU session reference information from the second communication network; The second PDU session information is generated based on the first PDU session information and the PDU session reference information.

9. The method according to claim 8, characterized in that, The step of obtaining the PDU session reference information of the second communication network includes: The PDU session reference information sent by the network device corresponding to the second communication network is obtained through the connection interface between the network device and the second communication network. Alternatively, obtain the subscription information of the second communication network sent by the operator's equipment; and obtain the PDU session reference information from the subscription information of the second communication network.

10. The method according to claim 7, characterized in that, The first PDU session information includes a first information element, which includes one of the following: the maximum number of supported packet filters, the PDU session always-on request, the maximum data rate for integrity protection, and PDU session management capabilities.

11. The method according to claim 10, characterized in that, The first information element is a newly added information element in the PDN connection request of the first communication network; Alternatively, the first information element may be a newly added information element in the protocol configuration options of the PDN connection request of the first communication network.

12. The method according to claim 10, characterized in that, The second PDU session information includes a second information element generated based on the first information element; or, an acknowledgment response to the first information element.

13. The method according to any one of claims 10-12, characterized in that, The first PDU session information also includes a third information element, which includes at least one of the following: PDU session identifier, request QoS rule, request QoS flow description; The fourth information element included in the second PDU session information is generated based on the third information element; The second PDU session information also includes: the maximum number of supported packet filters, PDU session persistent online requests, maximum data rate for integrity protection, and PDU session management capabilities.

14. A mobility management device, applied to a terminal device, characterized in that, The device includes: The first communication unit is configured to: send a PDN connection request for a first communication network; wherein the PDN connection request includes first PDU session information for the terminal device to establish a PDU session on a second communication network; The first communication unit is further configured to: receive a PDN connection response corresponding to the PDN connection request, and establish a PDN connection on the first communication network; wherein the PDN connection response includes second PDN session information determined based on the first PDU session information; the second PDU session information includes a fourth information element, the fourth information element including at least one of the following: network slice parameters, QoS rules, maximum bit rate of session aggregation, PDU session address lifetime, QoS flow description, QoS rules with a length of two octets, and QoS flow description with a length of two octets; The storage unit is used to store the session information of the second PDU.

15. A mobility management device, applied to network equipment, characterized in that, The device includes: The second communication unit is configured to: receive a PDN connection request from the first communication network; wherein the PDN connection request includes first PDU session information for establishing a PDU session on the second communication network; The processing unit is configured to: determine second PDU session information based on the first PDU session information; generate a PDN connection response based on the second PDU session information; the second PDU session information includes a fourth information element, the fourth information element including at least one of the following: network slice parameters, QoS rules, maximum bit rate of session aggregation, PDU session address lifetime, QoS flow description, QoS rules with a length of two octets, and QoS flow description with a length of two octets. The second communication unit is further configured to: send the PDN connection response and establish a PDN connection on the first communication network.

16. A mobility management device, characterized in that, include: The processor and memory configured to store computer programs that can run on the processor. Wherein, when the processor is configured to run the computer program, it causes the mobility management device to perform the steps of the method according to any one of claims 1 to 13.

17. A communication system, characterized in that, The communication system includes: terminal equipment and network equipment; The terminal device is configured to: send a PDN connection request for a first communication network to the network device; wherein the PDN connection request includes first PDU session information for the terminal device to establish a PDU session on a second communication network; The network device is configured to: receive a PDN connection request from a first communication network; determine second PDN session information based on the first PDU session information; generate a PDN connection response based on the second PDU session information; send the PDN connection response to the terminal device, and establish a PDN connection with the terminal device on the first communication network; the second PDU session information includes a fourth information element, which includes at least one of the following: network slice parameters, QoS rules, maximum bit rate of session aggregation, PDU session address lifetime, QoS flow description, QoS rules with a length of two octets, and QoS flow description with a length of two octets; The terminal device is also used to: store the second PDU session information.

18. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a computer, it causes the computer to perform the steps of the method described in any one of claims 1 to 13.

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