Network access method, system and device of 5G core network and medium

Abstract

Disclosed are a network access method, system, device and medium for a 5G core network, which relate to the technical field of 5G core networks, comprising: an SMF for controlling a UPF to establish a user plane tunnel through an N4 interface in a PDU session establishment process initiated by a 5G terminal, interacting with a PGW packet data network gateway of a 4G core network through a GTP-Cv2 protocol, and establishing a data forwarding channel between the UPF and a PGW; and the UPF is used for carrying out GTP message format conversion between the 5G network and the 4G core network, converting the 5G GTP message from the 5G base station into a 4G GTP message format, sending the 4G GTP message format to the PGW, converting the 4G GTP message from the PGW into a 5G GTP message format, and sending the 5G GTP message format to the 5G base station. According to the invention, on the basis of not changing the existing 4G operator core network EPC, the 5G base station and the 5G terminal can be quickly accessed through the 5G core network.

Description

Technical Field

[0001] This invention relates to the field of 5G core network technology, and in particular to a network access method, system, device and medium for 5G core network. Background Technology

[0002] In many existing operator networks in Africa and Central Asia, 4G core network EPC equipment from numerous equipment vendors is used for data services.

[0003] Some operators have a need for 5G SA base station access. Building a new 5GC core network on top of the existing 4G core network would be very expensive. Furthermore, building a new 5G network requires interoperability with the 4G network, as well as smooth handover, unified billing, and lawful eavesdropping capabilities. This results in many new interfaces being added between the 5G core network and the existing 4G core network, making network configuration complex and hindering rapid capacity expansion during network access. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of the prior art by providing a network access method, system, device, and medium for a 5G core network, thereby solving the problems in the prior art.

[0005] The present invention specifically provides the following technical solution: A network access method for a 5G core network, wherein the network elements of the 5G core network include SMF and UPF, and the implementation method includes: 5G terminals send Packet Data Unit (PDU) session establishment requests to the core network equipment AMF via 5G base stations; The AMF sends a service interface message to the Session Management Function (SMF), and the SMF sends an N4 interface session establishment or modification request message to the User Plane Function (UPF). After establishing a session with the user plane, the SMF sends a GTPC-v2 message to the 4G gateway PGW network element to establish a session request message. After the PGW replies, a session response is established, completing the uplink channel establishment and uplink data transmission. The uplink data is sent to the UPF via the 5G base station. The UPF converts the 5G GTP packets in the uplink data into 4G GTP packet format and sends them to the PGW. It also converts the 4G GTP packets from the PGW into 5G GTP packet format and sends them to the 5G base station.

[0006] Preferably, the UPF converts the 5G GTP packets in the uplink data into 4G GTP packet format and sends them to the PGW, and converts the 4G GTP packets from the PGW into 5G GTP packet format and sends them to the 5G base station, specifically: When sending uplink data to the PGW, the PN flag in the 5G GTP header of the uplink data is set to 0, and the extension header part, including the Extension Header Length and Extension Header Content fields, is removed, and the data is converted into 4G GTP packet format. When sending 4G GTP message format data to a 5G base station, an extended header is added to the 4G GTP message according to the UE session information to form a 5G GTP message format containing a PDU Session Container.

[0007] Preferably, the step of establishing a session response after the PGW reply, completing the uplink channel establishment and uplink data transmission, specifically includes: PGW replies to SMF with a GTPC-v2 message to establish a session response message; The SMF replies to the AMF with the Namf_Communication_N1N2MessageTransfer message, and sends the N2 PDU Session Request message to the 5G base station gNB through the AMF; The gNB sends a PDU session establishment accept message to the UE. At this time, the 5G base station gNB replies with an N2 PDU session response message to the AMF, completing the uplink channel establishment and uplink data transmission.

[0008] Preferably, the 5G GTP header includes a fixed extended header structure, wherein the sequence number field and the next extended header type field are mandatory, and a PDU Session Container extended header is included; in the 4G GTP header, the sequence number, N-PDU number, and extended header are optional fields, and exist only when the corresponding flag bits are set.

[0009] Preferably, the PDU Session Container extension header includes at least one of the following fields: PDUType, QFI, RQI, PPP / PPI parameters, and UL / DL Sending End Mark.

[0010] This invention provides a network access system for a 5G core network, comprising: The initial request module is used by 5G terminals to send Packet Data Unit (PDU) session establishment requests to the core network equipment AMF via 5G base stations; The uplink data module is used to send service interface messages to the session management function (SMF) through the AMF, and send N4 interface session establishment or modification request messages to the user plane function (UPF) through the SMF. After establishing a session with the user plane, the SMF sends a GTPC-v2 message to the 4G gateway PGW network element to establish a session request message. After the PGW replies, a session response is established to complete the uplink channel establishment and uplink data transmission. The data transmission module is used to send uplink data to the UPF via the 5G base station. The UPF converts the 5G GTP packets in the uplink data into 4G GTP packet format and sends them to the PGW. It also converts the 4G GTP packets from the PGW into 5G GTP packet format and sends them to the 5G base station.

[0011] The present invention provides a computer device, including a memory and a processor. The memory stores a program, and when the program is executed by the processor, the processor performs the steps of the above-described 5G core network network access method.

[0012] The present invention provides a storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the above-described network access method for a 5G core network.

[0013] Compared with the prior art, the present invention has the following significant advantages: This invention proposes a network access method for a 5G core network. By connecting to a 5G base station and terminal at the front end, and establishing a session with the user plane, the SMF (Software-Defined Network Provider) sends a GTPC-v2 message to the 4G PGW (Power Gateway) network element to request the establishment of a session. The data stream is ultimately transmitted back to the existing operator's 4G core network PGW, ensuring that the data anchor point remains unchanged during 4G to 5G handover. Furthermore, the billing process can be reused from the 4G core network PGW. This solution allows for the access of 5G base stations and 5G terminals through the 5G core network without altering the existing 4G operator's core network EPC (Engineering, Procurement, and Construction). Uplink data is sent from the 5G base station to the UPF (Uplink Provider Function). The UPF converts the 5G GTP packets in the uplink data into 4G GTP packet format before sending them to the PGW, and also converts the 4G GTP packets from the PGW into 5G GTP packet format before sending them to the 5G base station. This enables the data traffic to be imported into the existing EPC's PGW anchor point, billing system, and legitimate eavesdropping system, reducing investment in the original expensive network and facilitating rapid 5G SA network expansion. Attached Figure Description

[0014] Figure 1 This is a diagram of the existing 5G core network architecture in the embodiments of the present invention; Figure 2 This is a diagram of a prior art 4G core network in the embodiments of the present invention; Figure 3 This is a diagram of the 4G core network and 5G core network convergence architecture in an embodiment of the present invention; Figure 4 This is an architectural diagram of the technology of the present invention in an embodiment of the present invention; Figure 5 This is an overall flowchart of an embodiment of the present invention; Figure 6 This is an SMF diagram from an embodiment of the present invention; Figure 7 This is a diagram of the 4G (GTPv1-U) message header format in an embodiment of the present invention; Figure 8 This is a diagram of the 5G (GTP-U over 5GS) message header format in an embodiment of the present invention; Figure 9 A flowchart of a network access method for a 5G core network provided by the present invention. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0016] A device and communication method for a 5G core network (5GC) are proposed. By defining a new architecture, process, and network element functions, and based on the existing 4G core network EPC, methods and devices for 5G access and handover are supplemented. Figure 3 As shown, this method involves connecting to 5G base stations and 5G mobile phones at the front end, and then converting signaling and data into interfaces for the 4G core network EPC PGW at the back end. The signaling and data are then integrated into the 4G core network EPC interface, reusing existing 4G billing and lawful eavesdropping interfaces. This method requires minimal modification to the existing deployed core network architecture, reducing the cost of deploying a 5G SA network, and allows for rapid deployment by reusing existing network billing and lawful eavesdropping interfaces.

[0017] A 5G core network is added to the existing 4G core network architecture, where the 4G core network architecture is as follows: Figure 2As shown, it is necessary to enable users to smoothly switch between 4G and 5G networks while maintaining consistent network billing. This requires integrating the various network elements of the 4G and 5G core networks into a single network. The 4G core network (EPC) adopts a flat design, connecting to the base station (eNodeB) via the S1 interface. Internal network elements interact through specific interfaces to achieve functions such as user access, mobility management, data forwarding, and policy control. Connection with the access network (E-UTRAN): eNodeB (base station): Connects to the core network via the S1 interface, divided into control plane (S1-MME) and user plane (S1-U); Core network internal element connections: Mobility Management Entity (MME) connects to the eNodeB via S1-MME, handling signaling such as user access, authentication, and tracking area updates; MME and SGSN (2G / 3G core network element) achieve cross-domain handover via S3 interface; MME and HSS obtain user subscription data (such as APN, QoS) via S6a interface; MME and S-GW transmit user context information via S11 interface. S-GW and P-GW forward data to external networks via S5 / S8 interface; P-GW and PCRF receive policy control commands via Gx interface; PCRF interacts with operator IP services (such as IMS, PSS) via Rx interface; P-GW interacts with operator IP services (such as IMS, PSS) via SGi.

[0018] Among them, the existing 5G core network architecture is as follows: Figure 1 As shown. The UE connects to the AMF via the N1 interface for access control and mobility management; it connects to the (R)AN radio access network via the N2 interface for radio signal transmission. The (R)AN, as a radio signal access node, communicates with the UE via the N2 interface and connects to the UPF via the N3 interface for data forwarding. The AMF interacts with the UE via the N1 interface and with the (R)AN via the N2 interface, and is responsible for access control and mobility management. The SMF interacts with the UPF via the N4 interface and with the UDM via the N11 interface, and is responsible for session management. The UPF interacts with the (R)AN via the N3 interface and with the DN (Data Network) via the N6 interface, and is responsible for data forwarding and QoS processing. The UDM interacts with the SMF via the N11 interface to store user subscription data. The PCF interacts with the SMF via the N14 interface to provide policy control rules. The AF (Application Function) interacts with the PCF via the N8 interface to define service policy requirements. The NEF (Network Open Function) allows external applications to access network capabilities. The NRF (Network Memory Function) is responsible for network function service registration and discovery. The NSSF (Network Slice Selection Function) is responsible for network slice selection.

[0019] The converged architecture of 4G core network and 5G core network is as follows Figure 3As shown. Because the handover between 4G and 5G is involved, the anchor point needs to remain unchanged during the handover process. Therefore, the UPF and PGW-U need to be co-located, and the 4G PGW equipment must also have UPF functionality. Among these, Figure 3 The specific relationships are as follows:

[0020] The UE accesses the network via E-UTRAN. E-UTRAN connects to the MME via the S1-MME interface. The MME connects to the SGW via the S11 interface. The SGW connects to the SMF+PGW-C (session management function + PDN gateway control plane, 4G / 5G convergence) via the S5-C interface. The MME connects to the HSS+UDM (home subscriber server + unified data management, 4G / 5G convergence) via the S6a interface. The MME connects to the AMF (4G and 5G core network) via the N26 interface, enabling interoperability between the 4G and 5G core networks. The SMF+PGW-C connects to the UPF+PGW-U (user plane function + PDN gateway user plane, 4G / 5G convergence) via the N4 (5G) interface and the S5-C interface (4G control plane). (G / 5G convergence) SMF+PGW-C connects to PCF (Policy Control Function, 5G) via N7 interface, and UPF+PGW-U connects to SWG via S5-U interface (4G user plane). Simultaneously, UE accesses via NG-RAN (5G Radio Access Network), which connects to UPF+PGW-U via N3 interface (user plane) and to AMF via N2 interface (control plane). UE communicates logically with AMF via N1 interface (NAS signaling). AMF connects to SMF+PGW-C via N11 interface, to HSS+UDM (Unified Data Management) via N8 interface, and to PCF via N15 interface.

[0021] In actual operator networks, many operators in Africa and Central Asia have purchased core network EPCs from numerous existing operators. If they want to add 5G SA base stations, they need to purchase a lot of 5GC core network equipment such as AMF, SMF, and UPF, which is expensive and requires very complex configuration with the existing network EPCs. Even upgrading 4G PGW equipment to have UPF functionality requires a lot of money. The high cost is the main reason hindering local operators from developing 5G.

[0022] like Figure 4 As shown, this invention proposes a method and strategy for a 5G core network (5GC). By connecting to 5G base stations and 5G terminals at the front end, the back end converts 5G processes and data packets into 4G signaling processes and data packets, enabling seamless integration with the existing 4G core network EPC. This solution is simple to configure and does not require upgrading existing EPC equipment, thus incurring no additional upgrade costs.

[0023] The newly defined SMF and UPF are key innovations.

[0024] New interface added: The interface between the 5G core network element SMF and the 4G core network element PGW: uses the GTPC-v2 message format, see 3GPP TS29274 (previously there was no interface between SMF and PGW).

[0025] The interface between the 5G core network element UPF and the 4G core network element PGW uses GTP message forwarding.

[0026] The GTP messages of the PGW (Packet Data Network Gateway in 4G EPC) and the GTP messages of the UPF (User Plane Function in 5GC) have different encapsulation formats, requiring GTP message encapsulation format conversion in the UPF. The PGW of the 4G core network element transmits data with the SGW in the 4G EPC using the GTPC-v2 message format. The PGW connects to the Policy and Charging Rules Function Unit (PCRF) and sends information to the Internet via the SGI communication protocol. The SGW connects to the MME and the 4G base station eNB.

[0027] Existing technologies: 4G (GTPv1-U) is based on GTPv1 (TS 29.060), while 5G (GTP-U over 5GS) is based on the newer GTPv1 (TS 29.281, 38.415). In 4G, the TEID header is the core, with other information added as needed. The 5G GTP header has a fixed sequence number and extension header mechanism, and mandates the inclusion of a PDU session container extension header containing key information such as QFI, to flexibly support advanced 5G features. The mentioned "Next extension header type" and "Extension header (PDUSession container)" embody this mandatory extension header structure in 5G.

[0028] like Figure 5 and Figure 9 As shown, this invention provides a network access method for a 5G core network, wherein the network elements of the 5G core network include SMF and UPF, and the implementation method includes the following steps: Step S1: The 5G terminal UE sends a Packet Data Unit (PDU) Session Establishment Request to the core network equipment AMF through the 5G base station gNB.

[0029] Step S2: Send a service interface message to the Session Management Function (SMF) through the AMF, and send an N4 interface session establishment or modification request message to the User Plane Function (UPF) through the SMF. After establishing a session with the user plane, the SMF sends a GTPC-v2 message to the 4G gateway PGW network element to establish a session request message. After the PGW replies, a session response is established, completing the uplink channel establishment and uplink data transmission.

[0030] Step S2 is as follows: AMF sends an Nsmf_PDUSession_CreateSMContext Request message to SMF, which is a RESTful HTTP service interface message.

[0031] SMF sends an N4 Session Establishment / Modification Request message to UPF.

[0032] UPF responds to the N4 interface session establishment / modification response message.

[0033] The SMF needs to send a GTPC-v2 message to the 4G PGW network element again to establish a session request (Create SessionRequest) to notify the PGW and UPF to establish a data forwarding channel.

[0034] The PGW replies to the SMF with a GTPC-v2 Create Session Response message.

[0035] SMF replies to AMF with the Namf_Communication_N1N2MessageTransfer message.

[0036] AMF sends an N2 PDU Session Request (NAS msg) message to the 5G base station gNB.

[0037] The gNB sends a PDU Session Establishment Accept message to the UE.

[0038] The 5G base station gNB replies to the AMF with an N2 PDU Session Response message.

[0039] At this point, the uplink channel is established, and the first uplink data can be sent to the UPF via the UE and gNB. The UPF then converts the GTP data packet format and sends it to the 4G PGW network element. The PGW removes the GTP header from the data packet and sends it to the internet via the SGI communication protocol.

[0040] Step S3: The uplink data is sent to the UPF via the 5G base station. The UPF converts the 5G GTP packets in the uplink data into 4G GTP packet format and sends them to the PGW. The UPF also converts the 4G GTP packets from the PGW into 5G GTP packet format and sends them to the 5G base station.

[0041] Step S3 is as follows: AMF sends an Nsmf_PDUSession_UpdateSMContext Request message to SMF.

[0042] SMF sends an N4 Session Modification Request message to UPF.

[0043] UPF replies to SMF with an N4 Session Modification Response message.

[0044] SMF needs to send a GTPC-v2 message to the 4G PGW network element again to notify the PGW and UPF to update the data forwarding channel.

[0045] The PGW replies to the SMF with a GTPC-v2 message, "Modify Bearer Response".

[0046] Once the downlink channel is established, the first downlink data can be sent via a 4G PGW to the UPF via a GTP message. The UPF then converts the data format to meet 5G GTP message requirements and sends it to the gNB and UE.

[0047] SMF sends an Nsmf_PDUSession_UpdateSMContext Response message to AMF.

[0048] The innovative aspects of the above process are: SMF is as follows: Figure 6As shown: For SMF processing, in addition to supporting the PFCP message interface with the UPF, the SMF also needs to add an interface with the 4G PGW. The new interfaces are as follows: the SMF's GTPC, UDP, IP, L2, and L1 correspond one-to-one with the 4G PGW's GTPC, UDP, IP, L2, and L1.

[0049] SMF signaling logic: Upon receiving the AMF's Nsmf_PDUSession_CreateSMContext Request message, in addition to following the existing procedure of using FPCP messages to instruct the UPF to establish a tunnel, it also needs to interact with the 4G core network's PGW using the GTPC-v2 protocol via Create Session Request / Response. This instructs the UPF and PGW to transmit data.

[0050] UPF: It needs to convert GTP messages and forward them to the 4G PGW.

[0051] 5G GTP message format: The GTP message header contains Flags, Message Type, Length, TEID, Nextextension header type, and Extension header (PDU Session container).

[0052] 4G GTP message format: The GTP message header contains Flags, Message Type, Length, and TEID.

[0053] The UPF receives 5G GTP data packets from the gNB, needs to convert them into 4G GTP data packet format, and then send them to the PGW. Simultaneously, the UPF receives 4G GTP data packets from the PGW, needs to convert them into 5G GTP data packet format, and then send them to the 5G base station gNB.

[0054] In existing technologies, 5G GTP-U headers have introduced an extended header mechanism to support more new functions (such as reflection QoS, network slicing, etc.), making them more complex than 4G GTP-U headers.

[0055] like Figure 7 As shown, the 4G (GTPv1-U) message header format is as follows: This is the GTP-U protocol version (GTPv1-U) used for user plane data transmission in 4G EPC. Its standard message header structure is as follows:

[0056] Field Explanation: Flags (8 bits): Version (3 bits): Fixed at 1. PT (1 bit): Protocol type. 1 indicates GTP, 0 indicates GTP'. * (1 bit): Reserved bit. E (1 bit): Extension header flag. 1 indicates the presence of an extension header. S (1 bit): Sequence number flag. 1 indicates the presence of a sequence number. PN (1 bit): N-PDU number flag. 1 indicates the presence of an N-PDU number. Message Type (8 bits): Message type. For user plane data, it is usually 0xFF (T-PDU). Length (16 bits): Length of the remaining part of the message (excluding the first 8 bytes of fixed header). TEID (32 bits): Tunnel endpoint identifier, used to uniquely identify a GTP tunnel. Sequence Number (16 bits): Optional field, used for message ordering and duplicate detection. N-PDU Number (8 bits): Optional field, used to support cross-system handover. Next ExtensionHeader Type (8 bits): Optional field. If an extension header is present (E flag=1), this field indicates the type of the next extension header. If it does not exist, the value is 0.

[0057] Key point: In 4G, the serial number, N-PDU number, and extension header are all optional and will only appear when the corresponding flag bit is set.

[0058] like Figure 8 As shown, the 5G (GTP-U over 5GS) message header format: The 5G system adopts an updated version of the GTP-U protocol (based on 3GPP TS 29.281 and TS 38.415). Its message header has been redesigned to support the new features of the 5G core network.

[0059] Key differences and explanations: 1. Fixed extension header structure: In 5G, the serial number field and the next extension header type field are mandatory. This means that the S flag is always set to 1 in 5G GTP-U.

[0060] The PN (N-PDU Number) flag is not used in 5G; this field has been redefined as Spare.

[0061] 2. New Extension Header: 5G introduces the PDU Session Container as a mandatory extension header. It carries crucial information in the 5G user plane.

[0062] The PDU session container contains the following key fields: PDU Type (3 bits): Indicates the type of PDU (e.g., DL PDU SESSION INFORMATION, UL PDU SESSION INFORMATION, etc.). QFI (6 bits): QoS Flow Identifier, which is the core of the 5G QoS model and is used to identify different QoS flows. RQI (1 bit): Reflective QoS Indicator, used for reflecting QoS. PPP (1 bit) / PPI (3 bits): QoS-related parameters. UL / DL Sending End Mark: Used to mark the end of uplink or downlink data.

[0063] UPF conversion process: When the UPF of the 5G core network sends a GTP message to the PGW of the 4G core network, it modifies PN=0 and removes ExtensionHeader Length and Extension Header Content, converting the 5G (GTP-U over 5GS) message header format into the 4G (GTPv1-U) message header format before sending it to the PGW of the 4G core network.

[0064] When the 5G core network's UPF receives a GTP message from the 4G core network's PGW, it will supplement the UE's information with Extension Header Length and Extension Header Content, forming a 5G (GTP-U over 5GS) message header format, and then send it to the 5G base station gNB.

[0065] Explanation of the technology's application products and terminology: ENB - Evolved Node B; or Evolved Access Point. EPC - Evolved Packet Core. PLMN - Public Land Mobile Network. MME - Mobility Management Entity. CPE - Customer Premises Equipment. UE - User Equipment. PGW - Packet Data Network Gateway. 3GPP - 3rd Generation Partnership Project. eNodeB - Evolved Node B. SGW - Radio Resource Control. NAS - Non-Access Stratum. S1AP - S1 Application Protocol.

[0066] Based on the above statements, the present invention also provides a network access system for a 5G core network, wherein the network elements of the 5G core network include SMF and UPF, and the system includes: The initial request module is used by the 5G terminal to send a Packet Data Unit (PDU) session establishment request to the core network equipment AMF through the 5G base station; the uplink data module is used to send a service interface message to the Session Management Function (SMF) through the AMF, and send an N4 interface session establishment or modification request message to the User Plane Function (UPF) through the SMF. After establishing a session with the user plane, the SMF sends a GTPC-v2 message to the 4G gateway PGW network element to establish a session request message. After the PGW replies, a session response is established, completing the uplink channel establishment and uplink data transmission; the data transmission module is used to send uplink data to the UPF through the 5G base station. The UPF converts the 5G GTP packets in the uplink data into 4G GTP packet format and sends them to the PGW, and converts the 4G GTP packets from the PGW into 5G GTP packet format and sends them to the 5G base station.

[0067] The present invention also provides a computer device, including a memory and a processor, wherein the memory stores a program, and when the program is executed by the processor, the processor performs the steps of a network access method for a 5G core network.

[0068] According to the disclosed embodiments, the computer device can communicate with one or more external devices (e.g., keyboard, pointing device, Bluetooth communication, etc.) or with any device that enables the computing device to communicate with one or more other computing devices (e.g., router, demodulator, etc.).

[0069] The present invention also provides a storage medium storing a computer program thereon, wherein the computer program, when executed by a processor, implements the steps of a network access method for a 5G core network.

[0070] According to the disclosed embodiments, the storage medium can be a non-volatile computer-readable storage medium, such as, but not limited to: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof. In this invention, the storage medium can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device.

[0071] The above description, in conjunction with specific preferred embodiments, provides a more detailed explanation of the present invention. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered to fall within the scope of protection of the present invention.

Claims

1. A network access method for a 5G core network, characterized in that, include: 5G terminals send Packet Data Unit (PDU) session establishment requests to the core network equipment AMF via 5G base stations; The AMF sends a service interface message to the Session Management Function (SMF), and the SMF sends an N4 interface session establishment or modification request message to the User Plane Function (UPF). After establishing a session with the user plane, the SMF sends a GTPC-v2 message to the 4G gateway PGW network element to establish a session request message. After the PGW replies, a session response is established, completing the uplink channel establishment and uplink data transmission. The uplink data is sent to the UPF via the 5G base station. The UPF converts the 5G GTP packets in the uplink data into 4G GTP packet format and sends them to the PGW. It also converts the 4G GTP packets from the PGW into 5G GTP packet format and sends them to the 5G base station.

2. The network access method for a 5G core network as described in claim 1, characterized in that, The UPF converts the 5G GTP packets in the uplink data into 4G GTP packet format and sends them to the PGW, and converts the 4G GTP packets from the PGW into 5G GTP packet format and sends them to the 5G base station. Specifically: When sending uplink data to the PGW, the PN flag in the 5G GTP header of the uplink data is set to 0, and the extension header part, including the Extension Header Length and Extension Header Content fields, is removed, and the data is converted into 4G GTP packet format. When sending 4G GTP message format data to a 5G base station, an extended header is added to the 4G GTP message according to the UE session information to form a 5G GTP message format containing a PDU Session Container.

3. The network access method for a 5G core network as described in claim 1, characterized in that, The process of establishing a session response after the PGW reply, completing the uplink channel establishment and uplink data transmission, specifically involves: PGW replies to SMF with a GTPC-v2 message to establish a session response message; The SMF replies to the AMF with the Namf_Communication_N1N2MessageTransfer message, and sends the N2 PDU Session Request message to the 5G base station gNB through the AMF; The gNB sends a PDU session establishment accept message to the UE. At this time, the 5G base station gNB replies with an N2 PDU session response message to the AMF, completing the uplink channel establishment and uplink data transmission.

4. A network access method for a 5G core network as described in claim 1, characterized in that, The 5G GTP header contains a fixed extended header structure, in which the sequence number field and the next extended header type field are mandatory, and a PDUssion Container extended header is included; in the 4G GTP header, the sequence number, N-PDU number and extended header are optional fields, and they only exist when the corresponding flag bits are set.

5. A network access method for a 5G core network as described in claim 4, characterized in that, The PDU SessionContainer extension header contains at least one of the following fields: PDU Type, QFI, RQI, PPP / PPI parameters, and UL / DLSending End Mark.

6. A network access system for a 5G core network as described in claim 1, characterized in that, include: The initial request module is used by 5G terminals to send Packet Data Unit (PDU) session establishment requests to the core network equipment AMF via 5G base stations; The uplink data module is used to send service interface messages to the session management function (SMF) through the AMF, and send N4 interface session establishment or modification request messages to the user plane function (UPF) through the SMF. After establishing a session with the user plane, the SMF sends a GTPC-v2 message to the 4G gateway PGW network element to establish a session request message. After the PGW replies, a session response is established to complete the uplink channel establishment and uplink data transmission. The data transmission module is used to send uplink data to the UPF via the 5G base station. The UPF converts the 5G GTP packets in the uplink data into 4G GTP packet format and sends them to the PGW. It also converts the 4G GTP packets from the PGW into 5G GTP packet format and sends them to the 5G base station.

7. A computer device, characterized in that, The device includes a memory and a processor, wherein the memory stores a program, and when the program is executed by the processor, the processor performs the steps of a network access method for a 5G core network as described in any one of claims 1-5.

8. A storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of a network access method for a 5G core network as described in any one of claims 1-5.

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