CN112243300B - Connection establishment method and device - Google Patents

Abstract

The invention provides a connection establishment method and device, which belong to the technical field of wireless communication. A connection establishment method, applied to a terminal, where the terminal is located within the coverage of a network in a first communication mode and/or a network in a second communication mode, the method comprising: establishing a first session with a network-side device in a first communication mode; acquiring the Indication information of the network-side device in the first communication mode, where the indication information is used to instruct the terminal to establish a transport layer path with the network-side device in the second communication mode before the first session is interrupted; Before a session is interrupted, a transport layer path with the network-side device in the second communication mode is established. The technical solution of the present invention can solve the problem of service interruption due to the inability to maintain the IP address in a simple and independent core network configuration scenario.

Description

Connection establishment method and device

technical field

The present invention relates to the technical field of wireless communication, in particular to a method and device for establishing a connection.

Background technique

In some scenarios, in order to simplify configuration, two independent core networks (4G core network and 5G core network) are deployed on the core network, and there is no interface to communicate with each other. The two networks independently carry 4G and 5G services.

During data transmission, if the terminal moves from the 5G coverage area to the 4G coverage area, the terminal provides 5G PS data connection on 5G, the 5G wireless signal quality deteriorates, the New Radio (NR) link is released, and the bottom layer reports the 5G PS data connection to the upper layer. The Protocol Data Unit (PDU) session (Session) is interrupted. After the upper layer of the terminal perceives that the 5G PDU Session is interrupted, the upper layer decides to enable the 4G session based on its own capabilities and other current wireless connection status, and the upper layer of the terminal applies it to the newly created 4G session. Initiate reestablishment of previously interrupted application layer services. If the terminal moves from the 4G coverage area to the 5G coverage area, the quality of the 4G wireless signal deteriorates, the Long Term Evolution (LTE) link is released, and the bottom layer reports to the upper layer that the 4G session is interrupted. Capabilities and other current wireless connection status, it is decided to enable 5GPDU Session, and the terminal high-level application initiates reconstruction of previously interrupted application layer services on the newly created 5G PDU Session. In this process, due to the simple and independent core network configuration, the IP address of the session cannot be maintained. After the session is interrupted on one network, the application layer re-initiates the session establishment on another network. The problems caused by the reconstruction after this kind of session interruption are:

1. The session is interrupted, and the application layer has no session recovery mechanism, which directly affects the user experience;

2. The session is interrupted, and the application layer has a session recovery mechanism, but the delay introduced by the new transmission control protocol (Transmission Control Protocol, TCP) link of the new network, and the decrease in throughput caused by TCP slow start will directly lead to a decrease in user experience .

Contents of the invention

The technical problem to be solved by the present invention is to provide a method and device for establishing a connection, which can solve the problem of service interruption due to unmaintainable IP addresses in a simple and independent core network configuration scenario.

In order to solve the above technical problems, embodiments of the present invention provide technical solutions as follows:

An embodiment of the present invention provides a method for establishing a connection, which is applied to a terminal, and the terminal is located within the coverage of the first communication mode network and/or the second communication mode network, and the method includes:

Establish a first session with the network side device in the first communication mode;

Acquiring indication information of the network-side device in the first communication mode, where the indication information is used to instruct the terminal to establish a transport layer path with the network-side device in the second communication mode before the first session is interrupted;

Before the first session is interrupted, a transport layer path is established with the network side device in the second communication mode.

Optionally, the indication information indicates that the network in the first communication mode and the network in the second communication mode are independently networked and have no intercommunication with each other.

Optionally, the acquiring the indication information of the network side device in the first communication mode includes:

The indication information is acquired during the process of establishing the first session or during the process of attaching to the network in the first communication mode.

Optionally, establishing the first session with the network side device in the first communication mode, and obtaining the indication information during the establishment of the first session includes:

sending a session establishment request to the network side device in the first communication mode;

receiving a session establishment request response from the network side device in the first communication mode, where the session establishment request response carries the indication information.

Optionally, acquiring the indication information during the process of attaching to the first communication mode network includes:

sending an attach request to the network side device in the first communication mode;

receiving an attach request reply from the network side device in the first communication mode, where the attach request reply carries the indication information.

Optionally, before establishing the first session with the network side device in the first communication mode, the method further includes:

Sending a session establishment request to the network side device in the first communication mode, where the session establishment request indicates that the session mode is SSC1;

Receive a session establishment denial request from the network side device in the first communication mode, where the session establishment denial request carries a reason value or session mode SSC3;

Sending a session establishment request to the network side device in the first communication mode again, where the session establishment request indicates that the session mode is SSC3.

Optionally, the first session is an SSC3 session.

Optionally, before sending the session establishment request to the network side device in the first communication mode, the method further includes:

It is detected that the signal strength of the first communication mode network is greater than the signal strength of the second communication mode network.

Optionally, before the first session is interrupted, establishing a transport layer path with the network side device in the second communication mode includes:

detecting signal strengths of said first communication mode network and said second communication mode network;

When the signal strength of the network in the second communication mode is greater than the first threshold, establish a second session with the network side device in the second communication mode, and establish a transport layer path with the network side device in the second communication mode;

The first session is released when the signal strength of the network in the first communication mode is less than a second threshold, and the second threshold is less than the first threshold.

Optionally, the establishment of the transport layer path with the network side device in the second communication mode includes:

When the transport layer supports multi-path transmission, establish a new transmission subflow with the network side device in the second communication mode;

When the transport layer does not support multi-path transmission, establish a new TCP connection with the network side device in the second communication mode.

An embodiment of the present invention also provides a method for establishing a connection, which is applied to a network-side device in the first communication mode and/or the second communication mode, and the method includes:

Sending indication information to terminals within the coverage area, where the indication information is used to instruct the terminal to establish a connection with the network side device in the second communication mode before the first session with the network side device in the first communication mode is interrupted. Transport layer path.

Optionally, the sending the indication information to the terminals within the coverage includes:

The indication information is sent to the terminal during the session establishment process between the terminal and the network side device or during the attach process of the terminal.

Optionally, sending the indication information to the terminal during the session establishment process between the terminal and the network side device includes:

receiving a session establishment request from the terminal;

Sending a session establishment request response to the terminal, where the session establishment request response carries the indication information.

Optionally, sending the indication information to the terminal during the attach process of the terminal includes:

receiving an attach request from the terminal;

Sending an attach request response to the terminal, where the attach request response carries the indication information.

Optionally, the method also includes:

receiving a session establishment request from the terminal, where the session establishment request indicates that the session mode is SSC1;

Sending a session establishment rejection request to the terminal, where the session establishment denial request carries a reason value or session mode SSC3;

Receive a session establishment request sent again by the terminal, where the session establishment request indicates that the session mode is SSC3.

The embodiment of the present invention also provides a connection establishment device, which is applied to a terminal, and the terminal is located within the coverage of the first communication mode network and/or the second communication mode network, and the device includes a processor and a transceiver,

The processor is configured to establish a first session with a network side device in a first communication mode;

The transceiver is used to acquire indication information of the network-side device in the first communication mode, where the indication information is used to instruct the terminal to establish a connection with the network-side device in the second communication mode before the first session is interrupted. Transport layer path;

The processor is further configured to establish a transport layer path with the network side device in the second communication mode before the first session is interrupted.

Optionally, the indication information indicates that the network in the first communication mode and the network in the second communication mode are independently networked and have no intercommunication with each other.

Optionally, the transceiver is specifically configured to acquire the indication information during establishing the first session or attaching to the network in the first communication mode.

Optionally, the transceiver is specifically configured to send a session establishment request to the network side device in the first communication mode; receive a session establishment request response from the network side device in the first communication mode, and the session establishment request response carries There are instructions for that.

Optionally, the transceiver is specifically configured to send an attach request to the network side device in the first communication mode; receive an attach request response from the network side device in the first communication mode, and the attach request response carries the Instructions.

Optionally, the transceiver is further configured to send a session establishment request to the network side device in the first communication mode, where the session establishment request indicates that the session mode is SSC1; and receive a session establishment rejection from the network side device in the first communication mode request, the rejection session establishment request carries a reason value or session mode SSC3; and the session establishment request is sent to the network side device in the first communication mode again, and the session establishment request indicates that the session mode is SSC3.

Optionally, the first session is an SSC3 session.

Optionally, before the transceiver sends a session establishment request to the network side device in the first communication mode, the processor detects that the signal strength of the network in the first communication mode is greater than that of the network in the second communication mode strength.

Optionally, the processor is specifically configured to detect signal strengths of the first communication mode network and the second communication mode network; when the signal strength of the second communication mode network is greater than a first threshold, the The network-side device in the second communication mode establishes a second session, and establishes a transport layer path with the network-side device in the second communication mode; when the signal strength of the network in the first communication mode is less than a second threshold, release the second session For one session, the second threshold is smaller than the first threshold.

Optionally, the processor is specifically configured to establish a new transmission subflow with the network side device in the second communication mode when the transport layer supports multi-path transmission; when the transport layer does not support multi-path transmission, Establish a new TCP connection with the network side device in the second communication mode.

An embodiment of the present invention also provides a connection establishment device, which is applied to a network side device in the first communication mode and/or the second communication mode, and the device includes a processor and a transceiver,

The transceiver is configured to send indication information to terminals within coverage, where the indication information is used to instruct the terminal to establish a connection with the network in the second communication mode before the first session with the network side device in the first communication mode is interrupted. The transport layer path between side devices.

Optionally, the transceiver is specifically configured to send the indication information to the terminal during a session establishment process between the terminal and the network side device or during an attach process of the terminal.

Optionally, the transceiver is specifically configured to receive a session establishment request from the terminal; and send a session establishment request response to the terminal, and the session establishment request response carries the indication information.

Optionally, the transceiver is specifically configured to receive an attach request from the terminal; and send an attach request response to the terminal, where the attach request response carries the indication information.

Optionally, the transceiver is further configured to receive a session establishment request from the terminal, the session establishment request indicating that the session mode is SSC1; and sending a session establishment denial request to the terminal, the session establishment denial request carrying a reason value or session mode SSC3; receiving a session establishment request sent again by the terminal, where the session establishment request indicates that the session mode is SSC3.

An embodiment of the present invention also provides a communication device, including: a memory, a processor, and a computer program stored on the memory and operable on the processor. When the computer program is executed by the processor, the above-mentioned A step in a connection establishment method.

An embodiment of the present invention also provides a computer-readable storage medium, where a computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, the steps in the connection establishment method described above are implemented.

Embodiments of the present invention have the following beneficial effects:

In the above solution, the network side instructs the terminal to establish the underlying dual path for the service in advance before the single network session is interrupted, triggering the establishment of multipath at the transport layer, so as to provide the terminal with a service experience without reconnection delay in which the IP changes but the service is not interrupted , which solves the problem of service interruption due to IP address failure in a simple and independent core network configuration scenario.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings that need to be used in the description of the embodiments of the present invention. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention , for those skilled in the art, other drawings can also be obtained according to these drawings without paying creative labor.

Fig. 1 is the schematic diagram of the protocol stack of TCP;

Fig. 2 is the schematic diagram of the protocol stack of MPTCP;

FIG. 3 is a schematic diagram of MPTCP dual paths;

Figure 4 is a schematic diagram of the QUIC dual path;

FIG. 5 is a diagram of an intercommunication architecture with an N26 interface;

Figure 6 is an interworking architecture diagram without an N26 interface;

Figure 7 is a schematic diagram of an independent networking mode under simple configuration;

FIG. 8 is a schematic flowchart of a connection establishment method applied to a terminal according to an embodiment of the present invention;

FIG. 9 is a schematic flowchart of a connection establishment method applied to a network side device according to an embodiment of the present invention;

FIG. 10 is a schematic diagram of a terminal moving process according to Embodiment 1 of the present invention;

FIG. 11 is a schematic diagram of sending simplified configuration independent networking indication information by the network side according to Embodiment 1 of the present invention;

FIG. 12 is a schematic diagram of establishing a dual path according to an embodiment of the present invention;

FIG. 13 is a schematic diagram of session mode negotiation between the terminal and the network side in Embodiment 2 of the present invention;

Fig. 14 is a schematic diagram of the establishment of dual channels according to Embodiment 2 of the present invention;

FIG. 15 is a schematic diagram of a mobile process of a third terminal according to an embodiment of the present invention;

Fig. 16 and Fig. 17 are the schematic diagrams of the establishment of three pairs of channels according to the embodiment of the present invention;

FIG. 18 is a schematic diagram of a four-terminal mobile process according to an embodiment of the present invention;

FIG. 19 and FIG. 20 are schematic diagrams of establishing dual channels in Embodiment 4 of the present invention;

FIG. 21 is a structural block diagram of an apparatus for establishing a connection applied to a terminal according to an embodiment of the present invention;

Fig. 22 is a structural block diagram of an apparatus for establishing a connection applied to a network side device according to an embodiment of the present invention.

Detailed ways

In order to make the technical problems, technical solutions and advantages to be solved by the embodiments of the present invention clearer, the following will describe in detail with reference to the drawings and specific embodiments.

Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the drawings, it should be understood that the invention may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided for more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

The terms "first", "second" and the like in the specification and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It is to be understood that the data so used are interchangeable under appropriate circumstances such that the embodiments of the application described herein can be practiced in sequences other than those illustrated or described herein. Furthermore, the terms "comprising" and "having", as well as any variations thereof, are intended to cover a non-exclusive inclusion, for example, a process, method, system, product or device comprising a sequence of steps or elements is not necessarily limited to the expressly listed instead, may include other steps or elements not explicitly listed or inherent to the process, method, product or apparatus. "And/or" in the specification and claims means at least one of the connected objects.

The techniques described herein are not limited to Long Term Evolution (LTE)/LTE-Advanced (LTE-A) systems, and can also be used in various wireless communication systems, such as Code Division Multiple Access (Code Division Multiple Access) Access, CDMA), Time Division Multiple Access (Time Division Multiple Access, TDMA), Frequency Division Multiple Access (Frequency Division Multiple Access, FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier Frequency Division Multiple Access Address (Single-carrier Frequency-Division Multiple Access, SC-FDMA) and other systems. The terms "system" and "network" are often used interchangeably. A CDMA system may implement radio technologies such as CDMA2000, Universal Terrestrial Radio Access (UTRA), and the like. UTRA includes Wideband CDMA (Wideband Code Division Multiple Access, WCDMA) and other CDMA variants. A TDMA system can implement a radio technology such as Global System for Mobile Communication (GSM). The OFDMA system can implement radios such as UltraMobile Broadband (UMB), Evolution-UTRA (Evolution-UTRA, E-UTRA), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM, etc. technology. UTRA and E-UTRA are part of Universal Mobile Telecommunications System (UMTS). LTE and LTE-Advanced (like LTE-A) are new UMTS releases that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described in documents from an organization named "3rd Generation Partnership Project" (3GPP). CDMA2000 and UMB are described in documents from an organization named "3rd Generation Partnership Project 2" (3GPP2). The techniques described herein may be used for the systems and radio technologies mentioned above as well as other systems and radio technologies. However, the following description describes NR systems for example purposes, and NR terminology is used in much of the following description, although the techniques are applicable to applications other than NR system applications as well.

The following description provides examples and does not limit the scope, applicability or configuration set forth in the claims. Changes may be made in the function and arrangement of elements discussed without departing from the spirit and scope of the disclosure. Various examples may omit, substitute, or add various procedures or components as appropriate. For example, the methods described may be performed in an order different from that described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

Multipath TCP (MultiPathTCP, MPTCP) allows TCP connections to use multiple paths to maximize channel resource usage. The core idea of MPTCP is to define a way to establish a connection between two hosts, not between two interfaces. In TCP, a connection is established between two IP addresses, and each TCP connection is identified by a four-tuple identifying the address and port of the source and destination. In view of this limitation, the application can only create one TCP connection through a single connection, so although multiple connections may be established between two hosts at the same time, only a single connection is used by an application at the same time, while Multipath TCP allows The connection uses multiple paths at the same time. To this end, MultipathTCP creates a TCP connection called subflow on each path that needs to be used. Figure 1 and Figure 2 are schematic diagrams of the protocol stacks of TCP and MPTCP respectively, and Figure 3 is the dual path of MPTCP schematic diagram.

Quick UDP Internet Connection (Quick UDP Internet Connection, QUIC) is a low-latency Internet transport layer protocol based on the User Datagram Protocol (User Datagram Protocol, UDP). QUIC is implemented through the connection ID of the QUIC header. Data packet aggregation supports multi-path. Figure 4 is a schematic diagram of QUIC dual-path.

Relevant communication standards define three session modes: session and service continuity (Session and Service continuity, SSC) 1, SSC2 and SSC3. The session mode is determined through negotiation between the terminal (User Equipment, UE) and the core network when the session is established. The UE provides the session mode, but the final determined session mode is determined by the session management function entity (SMF, Session Management Function).

The SSC1 session means that from the beginning to the end of the session, the UPF anchor point of the session does not change. For IPV4 or IPV6 services, the IP address can remain unchanged. SSC2 session means that the session can be released and then re-established. SSC3 session means to establish a new session before the old session is released, and then release the old session within a certain period of time.

As shown in Figure 5, in the interworking scenario defined by the relevant communication standards, the SMF of the 5G core network (5GC), the policy control function entity (PCF, Policy Control Function), the user plane function entity (UPF, User Plane Function), and the unified data Management (Unified Data Management, UDM) and 4G core network (Evolved Packet Core, EPC) public data network gateway control plane (PDN Gateway-C, PGW-C), policy and charging control entity (Policy and Charging Rules Function, PCRF ), the public data network gateway user plane (PDN Gateway-U, PGW-U), and the home subscriber server (Home Subscriber Server, HSS) are jointly established, but the mobility management entity (Mobility Management Entity, MME) and the mobility management functional entity The N26 interface between (AMF, Access and Mobility ManagementFunction) is optional.

In the N26 architecture scenario, the 4G and 5G core networks are tightly coupled, and the 5GC AMF and EPC MME communicate through the N26 interface; Switch UE context and session resources to the target side, maintaining IP address and business continuity.

In the interworking architecture scenario without N26 interface as shown in Figure 6, there is no interworking interface between 5GC and EPC. During the interoperability process, the core network on the target side obtains information such as the gateway address of the UE on the source side through the UE, and the UE Initiate the reconstruction of UE context and session resources on the target side, keeping the UE IP address unchanged.

The intercommunication scenarios defined by relevant communication standards are limited to the tightly coupled 4G and 5G core networks. Whether the context is passed through the N26 or saved through the UE, it is because of the joint setup of the UPF and the PGW that the IP address remains unchanged. Purpose.

In some scenarios, in order to simplify the configuration, as shown in Figure 7, two independent core networks (LTE EPC and 5GC) are deployed on the core network, and there is no interface to communicate with each other. The two networks independently carry 4G and 5G services. In 4G LTE and 5G NR wireless networks, handover and network reselection are not configured.

During data transmission, if the terminal moves from the 5G coverage area to the 4G coverage area, the terminal is providing 5G PS data connection on 5G, the 5G wireless signal quality deteriorates, the NR link is released, the bottom layer reports to the upper layer that the 5G PDU Session is interrupted, and the upper layer of the terminal After sensing the interruption of the 5G PDU Session, the upper layer decides to enable the 4G session based on its own capabilities and other current wireless connection status, and the terminal upper layer application initiates reconstruction of the previously interrupted application layer service on the newly created 4G session. If the terminal moves from the 4G coverage area to the 5G coverage area, the quality of the 4G wireless signal deteriorates, the LTE link is released, and the bottom layer reports to the upper layer that the 4G session is interrupted. It is decided to enable 5G PDUSession, and the terminal high-level application initiates reconstruction of the previously interrupted application layer service on the newly created 5G PDU Session. In this process, due to the simple and independent core network configuration, the IP address of the session cannot be maintained. After the session is interrupted on one network, the application layer re-initiates the session establishment on another network. The problems caused by the reconstruction after such session interruption are:

1. The session is interrupted, and the application layer has no session recovery mechanism, which directly affects the user experience;

2. The session is interrupted, and the application layer has a session recovery mechanism, but the delay introduced by the new TCP connection of the new network, and the decrease in throughput caused by TCP slow start will directly lead to a decrease in user experience.

In order to solve the above problems, embodiments of the present invention provide a method and device for establishing a connection, which can solve the problem of service interruption caused by IP address failure in a simple and independent core network configuration scenario.

An embodiment of the present invention provides a method for establishing a connection, which is applied to a terminal, and the terminal is located within the coverage of the first communication mode network and/or the second communication mode network. As shown in FIG. 8 , the method includes:

Step 101: Establish a first session with a network side device in the first communication mode;

Step 102: Obtain indication information of the network-side device in the first communication mode, where the indication information is used to instruct the terminal to establish a transport layer with the network-side device in the second communication mode before the first session is interrupted path;

Step 103: Before the first session is interrupted, establish a transport layer path with the network side device in the second communication mode.

In this embodiment, the network side instructs the terminal to pre-establish the underlying dual path for the service before the single network session is interrupted, triggering the establishment of multipath at the transport layer, so that the terminal can be provided with a service without reconnection delay that does not interrupt the service due to IP changes experience, which solves the problem of service interruption due to IP address failure in a simple and independent core network configuration scenario.

Optionally, the indication information indicates that the network in the first communication mode and the network in the second communication mode are independently networked and have no intercommunication with each other.

Optionally, the acquiring the indication information of the network side device in the first communication mode includes:

The indication information is acquired during the process of establishing the first session or during the process of attaching to the network in the first communication mode.

In a specific embodiment, the establishment of the first session with the network side device in the first communication mode, and obtaining the indication information during the establishment of the first session includes:

sending a session establishment request to the network side device in the first communication mode;

receiving a session establishment request response from the network side device in the first communication mode, where the session establishment request response carries the indication information.

In another specific embodiment, acquiring the indication information during the process of attaching to the first communication mode network includes:

sending an attach request to the network side device in the first communication mode;

receiving an attach request reply from the network side device in the first communication mode, where the attach request reply carries the indication information.

Optionally, before establishing the first session with the network side device in the first communication mode, the method further includes:

Sending a session establishment request to the network side device in the first communication mode, where the session establishment request indicates that the session mode is SSC1;

Receive a session establishment denial request from the network side device in the first communication mode, where the session establishment denial request carries a reason value or session mode SSC3;

Sending a session establishment request to the network side device in the first communication mode again, where the session establishment request indicates that the session mode is SSC3.

If the SSC mode in the UE's session establishment request is SSC1, the SMF with simplified configuration and independent networking needs to reject the session establishment request with a cause value, or directly reply to SSC3, instructing the UE to consider whether to re-initiate the session establishment request through SSC3 mode.

Optionally, the first session is an SSC3 session.

Optionally, before sending the session establishment request to the network side device in the first communication mode, the method further includes:

It is detected that the signal strength of the first communication mode network is greater than the signal strength of the second communication mode network.

Optionally, before the first session is interrupted, establishing a transport layer path with the network side device in the second communication mode includes:

detecting signal strengths of said first communication mode network and said second communication mode network;

When the signal strength of the network in the second communication mode is greater than the first threshold, establish a second session with the network side device in the second communication mode, and establish a transport layer path with the network side device in the second communication mode;

The first session is released when the signal strength of the network in the first communication mode is less than a second threshold, and the second threshold is less than the first threshold.

Optionally, the establishment of the transport layer path with the network side device in the second communication mode includes:

When the transport layer supports multi-path transmission, establish a new transmission subflow with the network side device in the second communication mode;

When the transport layer does not support multi-path transmission, establish a new TCP connection with the network side device in the second communication mode.

Specifically, the first communication mode may be one of 4G and 5G, and the second communication mode may be the other of 4G and 5G. The terminal can detect the signal strength in real time according to the indication information obtained from the core network. When moving from a single coverage area to a 4G and 5G dual coverage area, and the signal reaches the set threshold, it will initiate a session on the new network for the session in the original network Established to form a dual pathway. After the UE establishes the underlying dual path for the session on 4G and 5G, it triggers the transport layer to initiate dual-stream establishment. If the transport layer supports multi-path transmission, it triggers a new transmission sub-flow. For example, MPTCP adds a TCP sub-flow, and QUIC adds a sub-path , if the transport layer does not support multipath, such as traditional TCP services, directly initiate a new TCP connection, wait for the application layer data to be delivered, and then use the newly created TCP to send data.

In addition, the UE may also determine whether to initiate the establishment of the SSC1 session or switch to the SSC3 session in the simplified configuration independent networking according to the interaction or configuration of the application layer.

The embodiment of the present invention also provides a method for establishing a connection, which is applied to a network-side device in the first communication mode and/or the second communication mode. As shown in FIG. 9, the method includes:

Step 201: Send indication information to terminals within coverage, where the indication information is used to instruct the terminal to establish a connection with the network side device in the second communication mode before the first session with the network side device in the first communication mode is interrupted. transport layer paths between them.

Optionally, the indication information indicates that the network in the first communication mode and the network in the second communication mode are independently networked and have no intercommunication with each other.

Optionally, the sending the indication information to the terminals within the coverage includes:

The indication information is sent to the terminal during the session establishment process between the terminal and the network side device or during the attach process of the terminal.

In a specific embodiment, sending the indication information to the terminal during the session establishment process between the terminal and the network side device includes:

receiving a session establishment request from the terminal;

Sending a session establishment request response to the terminal, where the session establishment request response carries the indication information.

In another specific embodiment, sending the indication information to the terminal during the attach process of the terminal includes:

receiving an attach request from the terminal;

Sending an attach request response to the terminal, where the attach request response carries the indication information.

Optionally, the method also includes:

receiving a session establishment request from the terminal, where the session establishment request indicates that the session mode is SSC1;

Sending a session establishment rejection request to the terminal, where the session establishment denial request carries a reason value or session mode SSC3;

Receive a session establishment request sent again by the terminal, where the session establishment request indicates that the session mode is SSC3.

Specifically, the first communication mode may be one of 4G and 5G, and the second communication mode may be the other of 4G and 5G. When the 5G session is established, the 5G core network sends indication information to the UE, instructing the UE to access the network to simplify the configuration of independent networking. The indication information is used for the UE to detect the strength of 4G and 5G signals in real time and initiate dual connections; When the UE is attached, the network that the UE accesses is indicated to simplify the configuration of independent networking, and the indication information is used for the UE to detect the strength of 4G and 5G signals in real time according to the indication, and initiate dual connection.

If the SSC mode in the UE's session establishment request is SSC1, the SMF with simplified configuration and independent networking needs to reject the session establishment request with a cause value, or directly reply to SSC3, instructing the UE to consider whether to re-initiate the session establishment request through SSC3 mode.

The technical solution of the present invention is further introduced below in conjunction with specific embodiments:

Embodiment one:

As shown in Figure 10, when the UE initiates session establishment at point A covered by 5G alone, as shown in Figure 11, the 5G core network carries indication information in the response to the session establishment request, indicating that the network accessed by the UE is simplified configuration independent Networking, UE can detect the strength of 4G and 5G signals in real time according to the instruction information, and initiate dual connection.

As shown in Figure 12, when the UE moves from point A covered by 5G alone to point B covered by 4G and 5G dual coverage, all sessions are unified to initiate session establishment on 4G, forming a dual path with the 5G session that has not been disconnected. The process is as follows:

Step 1. Establish a 5G session 1 between the UE and the 5G core network, and the IP address is IP1;

Step 2. The UE performs signal monitoring according to the indication information received from the network side, and detects that the 4G signal strength reaches a certain threshold

Step 3, UE initiates 4G session establishment, IP address is IP2;

Step 4, UE. Trigger the transport layer to initiate dual-stream establishment. If the transport layer supports multi-path transmission, trigger the creation of a new transmission sub-flow. For example, MPTCP adds a TCP sub-flow, and QUIC adds a sub-path. If the transport layer does not support multi-path , such as traditional TCP services, directly initiate a new TCP connection, wait for the application layer data to be delivered, and then use the newly created TCP to send data;

Step 5. When the UE detects that the 5G signal continues to weaken to the set threshold, the 5G session 1 is released.

Embodiment two:

In this embodiment, the judgment of the conversation mode is added. Because for the session mode of SSC1, the IP address will change anyway, so the UE can only switch to the session mode of SSC3, or if the UE continues to use the session mode of SSC1, the network can only provide best-effort service at present. For the session mode of SSC2, IP Address changes and session interruptions have little effect, so no special handling is required.

When the UE initiates session establishment at point A covered by 5G alone, if the SSC mode in the UE's session establishment request is SSC1, then the SMF with simplified configuration and independent networking needs to reject the session establishment request and carry the reason value, or directly reply to SSC3, Instructs the UE to consider whether to re-initiate the session establishment request in SSC3 mode. As shown in Figure 13, the specific process includes the following steps:

Step 1. The UE sends a session establishment request to the SMF, which carries the PDU session ID and indicates that the SSC mode is SSC1;

Step 2. SMF determines that the network where it is located cannot support SSC1 sessions, which is to simplify the configuration of independent networking;

Step 3. The SMF sends a request to the UE to reject the session establishment, which carries a reason value or replies to SSC3, instructing the UE to consider whether to re-initiate the session establishment request through the SSC3 mode;

Step 4, UE judges whether to terminate the session request or continue to request SSC1, or use SSC3 to establish a session;

Step 5a, the UE can send a session establishment request to the SMF, which carries a PDU session ID and indicates that the SSC mode is SSC1;

In step 5b, the UE may also send a session establishment request to the SMF, which carries a PDU sessionID and indicates that the SSC mode is SSC3.

As shown in Figure 10, the UE moves from point A where 5G is solely covered to point B where 4G and 5G are dually covered. At this time, the UE detects a 4G signal. When the signal strength reaches a certain threshold (which can be greater than or equal to the threshold set by 5G to 4G handover), the UE registers on 4G and determines all SSC3 mode sessions currently in the 5G network. , and then initiate session establishment on 4G for these SSC3 sessions, and form a dual path with the 5G sessions that have not been disconnected. When the 5G signal continues to weaken until the session is interrupted, because of the establishment of the 4G session, for the SSC3 session, although the IP address changes, the service is not interrupted. As shown in Figure 14, its process includes the following steps:

Step 1. Establish a 5G session 1 between the UE and the 5G core network, the session mode is SSC3, and the IP address is IP1;

Step 2. The UE performs signal monitoring and detects that the 4G signal strength reaches a certain threshold

Step 3, UE registers in 4G, and initiates 4G session establishment, IP address is IP2;

Step 4. The UE triggers the transport layer to initiate dual-stream establishment. If the transport layer supports multi-path transmission, it triggers a new transmission sub-flow. For example, MPTCP adds a new TCP sub-flow, and QUIC adds a new sub-path;

Step 5. When the UE detects that the 5G signal continues to weaken to the set threshold, the 5G session 1 is released.

Embodiment three:

As shown in Figure 15, when the UE is in the 4G and 5G dual coverage area, such as point C, and creates a new session, the optional methods are as follows:

Method 1: The UE initiates session establishment in 4G and 5G at the same time, preventing the UE from moving from point C in the 4G and 5G dual coverage area to point D in the 4G single coverage area or from point C in the 4G and 5G dual coverage area to point E in the 5G single coverage area When the point is moved, the session is interrupted.

Method 2: UE is in the 4G and 5G dual coverage area, such as point C. When creating a new session, judge the signal strength. If the 5G signal is strong, establish a session on 5G. When point D in the 4G single coverage area moves, the 4G signal strength is detected, and when a certain threshold is reached, session establishment is initiated on 4G, as shown in Figure 16, and the process includes the following steps:

Step 0, the UE detects that the 5G signal strength is greater than the 4G signal;

Step 1. A 5G session is established between the UE and the 5G core network, and the IP address is IP1;

Step 2. The UE performs signal monitoring according to the indication information received from the network side, and detects that the 4G signal strength reaches a certain threshold

Step 3, UE registers in 4G, and initiates 4G session establishment, IP address is IP2;

Step 4. The UE triggers the transport layer to initiate dual-stream establishment. If the transport layer supports multi-path transmission, it triggers a new transmission sub-flow. For example, MPTCP adds a TCP sub-flow, and QUIC adds a sub-path. If the transport layer does not support multi-path, For traditional TCP services, directly initiate a new TCP connection, wait for the application layer data to be delivered, and then use the newly created TCP to send data;

Step 5. When the UE detects that the 5G signal continues to weaken to the set threshold, the 5G session 1 is released.

If the 4G signal is strong, establish a session on 4G. When the UE moves from point C in the 4G and 5G dual coverage area to point E in the 4G single coverage area, the 5G signal strength is detected. When a certain threshold is reached, the session establishment is initiated on 5G. As shown in Figure 17, its process includes the following steps:

Step 0, the UE detects that the 4G signal strength is greater than the 5G signal strength;

Step 1. Establish a 4G session 1 between the UE and the 4G core network, and the IP address is IP1;

Step 2. The UE performs signal monitoring and detects that the 5G signal strength reaches a certain threshold

Step 3, UE initiates 5G session establishment, IP address is IP2;

Step 4. The UE triggers the transport layer to initiate dual-stream establishment. If the transport layer supports multi-path transmission, it triggers a new transmission sub-flow. For example, MPTCP adds a TCP sub-flow, and QUIC adds a sub-path. If the transport layer does not support multi-path, For traditional TCP services, directly initiate a new TCP connection, wait for the application layer data to be delivered, and then use the newly created TCP to send data;

Step 5. When the UE detects that the 4G signal continues to weaken to the set threshold, the 4G session 1 is released.

Embodiment four:

As shown in Figure 18, when the UE initiates session establishment at point F of 4G independent coverage, the core network carries indication information in the response to the UE in the attach (Attach) process, indicating that the network that the UE accesses is a simplified configuration independent networking, It is used for the UE to detect the strength of 4G and 5G signals in real time according to the instructions, and initiate a dual connection, as shown in Figure 19. The process includes the following steps:

Step 1. The UE initiates an Attach process to the MME;

Step 2, GW determines the network where it is located, which is to simplify the configuration of independent networking;

Step 3: The MME sends indication information to the UE, indicating that the network the UE accesses is a simplified configuration independent networking.

As shown in Figure 18, when the UE is in the 4G single coverage area, such as point F, and moves to point G with 4G and 5G dual coverage, the UE detects that the 5G signal strength reaches a certain threshold according to the indication information sent by the network. All sessions of the UE in the 4G network initiate session establishment on 5G, and form a dual path with the 4G sessions that have not been disconnected. As shown in Figure 20, its process includes the following steps:

Step 1. Establish a 4G session 1 between the UE and the 4G core network;

Step 2. The UE performs signal monitoring according to the indication information received from the network side, and detects that the 5G signal strength reaches a certain threshold

Step 3. The UE registers on the 5G network and initiates the establishment of a 5G session with the IP address being IP2;

Step 4. The UE triggers the transport layer to initiate dual-stream establishment. If the transport layer supports multi-path transmission, it triggers a new transmission sub-flow. For example, MPTCP adds a TCP sub-flow, and QUIC adds a sub-path. If the transport layer does not support multi-path, For traditional TCP services, directly initiate a new TCP connection, wait for the application layer data to be delivered, and then use the newly created TCP to send data;

Step 5. When the UE detects that the 4G signal continues to weaken to the set threshold, the 4G session 1 is released.

The embodiment of the present invention also provides a connection establishment device, which is applied to a terminal, and the terminal is located within the coverage of the first communication mode network and/or the second communication mode network. As shown in FIG. 21 , the device includes a processor 31 and transceiver 32,

The processor 31 is configured to establish a first session with the network side device in the first communication mode;

The transceiver 32 is used to obtain indication information of the network-side device in the first communication mode, and the indication information is used to instruct the terminal to establish a connection with the network-side device in the second communication mode before the first session is interrupted. The transport layer path between;

The processor 31 is further configured to establish a transport layer path with the network side device in the second communication mode before the first session is interrupted.

In this embodiment, the network side instructs the terminal to pre-establish the underlying dual path for the service before the single network session is interrupted, triggering the establishment of multipath at the transport layer, so that the terminal can be provided with a service without reconnection delay that does not interrupt the service due to IP changes experience, which solves the problem of service interruption due to IP address failure in a simple and independent core network configuration scenario.

Optionally, the indication information indicates that the network in the first communication mode and the network in the second communication mode are independently networked and have no intercommunication with each other.

Optionally, the transceiver 32 is specifically configured to acquire the indication information during establishing the first session or attaching to the network in the first communication mode.

Optionally, the transceiver 32 is specifically configured to send a session establishment request to the network side device in the first communication mode; receive a session establishment request reply from the network side device in the first communication mode, and the session establishment request reply carry the indication information.

Optionally, the transceiver 32 is specifically configured to send an attach request to the network-side device in the first communication mode; receive an attach request response from the network-side device in the first communication mode, where the attach request response carries the instructions described above.

Optionally, the transceiver 32 is also configured to send a session establishment request to the network side device in the first communication mode, where the session establishment request indicates that the session mode is SSC1; and receive a session rejection from the network side device in the first communication mode Establishing a request, wherein the rejecting session establishment request carries a reason value or session mode SSC3; sending a session establishment request to the network side device in the first communication mode again, the session establishment request indicating that the session mode is SSC3.

Optionally, the first session is an SSC3 session.

Optionally, before the transceiver 32 sends a session establishment request to the network side device in the first communication mode, the processor detects that the signal strength of the network in the first communication mode is greater than that of the network in the second communication mode. signal strength.

Optionally, the processor 31 is specifically configured to detect the signal strengths of the first communication mode network and the second communication mode network; when the signal strength of the second communication mode network is greater than a first threshold, and The network-side device in the second communication mode establishes a second session, and establishes a transport layer path with the network-side device in the second communication mode; when the signal strength of the network in the first communication mode is less than a second threshold, release the In the first session, the second threshold is smaller than the first threshold.

Optionally, the processor 31 is specifically configured to establish a new transmission subflow with the network side device in the second communication mode when the transport layer supports multi-path transmission; when the transport layer does not support multi-path transmission , establishing a new TCP connection with the network-side device in the second communication mode.

The embodiment of the present invention also provides an apparatus for establishing a connection, which is applied to a network-side device in the first communication mode and/or the second communication mode. As shown in FIG. 22 , the apparatus includes a processor 41 and a transceiver 42,

The transceiver 42 is configured to send indication information to terminals within the coverage area, where the indication information is used to instruct the terminal to establish communication with the second communication mode before the first session with the network side device in the first communication mode is interrupted. The transport layer path between devices on the network side of the mode.

Optionally, the transceiver 42 is specifically configured to send the indication information to the terminal during a session establishment process between the terminal and the network side device or during an attach process of the terminal.

Optionally, the transceiver 42 is specifically configured to receive a session establishment request from the terminal; and send a session establishment request response to the terminal, and the session establishment request response carries the indication information.

Optionally, the transceiver 42 is specifically configured to receive an attach request from the terminal; and send an attach request response to the terminal, and the attach request response carries the indication information.

Optionally, the transceiver 42 is also configured to receive a session establishment request from the terminal, the session establishment request indicating that the session mode is SSC1; and sending a session establishment denial request to the terminal, the session establishment denial request carrying Cause value or session mode SSC3; receiving a session establishment request sent again by the terminal, where the session establishment request indicates that the session mode is SSC3.

An embodiment of the present invention also provides a communication device, including: a memory, a processor, and a computer program stored on the memory and operable on the processor. When the computer program is executed by the processor, the above-mentioned A step in a connection establishment method.

An embodiment of the present invention also provides a computer-readable storage medium, where a computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, the steps in the connection establishment method described above are implemented.

It should be understood that the embodiments described herein may be implemented by hardware, software, firmware, middleware, microcode or a combination thereof. For hardware implementation, the processing unit can be implemented in one or more application specific integrated circuits (Application Specific Integrated Circuits, ASIC), digital signal processor (Digital Signal Processing, DSP), digital signal processing device (DSP Device, DSPD), programmable logic Device (Programmable LogicDevice, PLD), Field-Programmable Gate Array (Field-Programmable Gate Array, FPGA), general-purpose processor, controller, microcontroller, microprocessor, other electronic units for performing the functions described in this application or a combination thereof.

For a software implementation, the techniques described herein can be implemented through modules (eg, procedures, functions, and so on) that perform the functions described herein. Software codes can be stored in memory and executed by a processor. Memory can be implemented within the processor or external to the processor.

Each embodiment in this specification is described in a progressive manner, each embodiment focuses on the difference from other embodiments, and the same and similar parts of each embodiment can be referred to each other.

Those skilled in the art should understand that the embodiments of the present invention may be provided as methods, devices, or computer program products. Accordingly, embodiments of the invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, embodiments of the invention may take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein.

Embodiments of the present invention are described with reference to flowcharts and/or block diagrams of methods, user terminal devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each procedure and/or block in the flowchart and/or block diagram, and a combination of procedures and/or blocks in the flowchart and/or block diagram can be realized by computer program instructions. These computer program instructions may be provided to a general-purpose computer, a special purpose computer, an embedded processor, or a processor of other programmable data processing user terminal equipment to produce a machine so that the computer or other programmable data processing user terminal equipment may execute The instructions generate means for realizing the functions specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions may also be stored in a computer readable memory capable of directing a computer or other programmable data processing user terminal equipment to operate in a specific manner, such that the instructions stored in the computer readable memory produce an article of manufacture comprising instruction means, The instruction means implements the functions specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions can also be loaded on a computer or other programmable data processing user terminal equipment, so that a series of operation steps are executed on the computer or other programmable user terminal equipment to produce computer-implemented processing, so that the computer or other programmable data processing The instructions executed on the user terminal equipment provide steps for realizing the functions specified in one or more procedures of the flow chart and/or one or more blocks of the block diagram.

Having described preferred embodiments of embodiments of the present invention, additional changes and modifications to these embodiments can be made by those skilled in the art once the basic inventive concept is appreciated. Therefore, the appended claims are intended to be construed to cover the preferred embodiment and all changes and modifications which fall within the scope of the embodiments of the present invention.

It should also be noted that in this article, relational terms such as first and second etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that these entities or operations Any such actual relationship or order exists between. Moreover, the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article or user terminal equipment comprising a series of elements includes not only those elements, but also includes not expressly other elements listed, or also include elements inherent to such a process, method, article, or user terminal equipment. Without further limitations, an element defined by the statement "comprising a..." does not exclude the existence of another same element in the process, method, article, or user terminal device that includes the element.

What has been described above is a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, some improvements and modifications can also be made without departing from the principles described in the present invention. within the scope of protection of the invention.

Claims (17)

1. A connection establishment method applied to a terminal, wherein the terminal is located in a coverage area of a first communication mode network and/or a second communication mode network, the method comprising:

establishing a first session with a first communication mode network side device;

acquiring indication information of the first communication mode network side equipment, wherein the indication information is used for indicating the terminal to establish a transmission layer path between the terminal and second communication mode network side equipment before the first session is interrupted;

before the first session is interrupted, establishing a transmission layer path between the first session and the network side equipment in the second communication mode;

before the first session is established with the first communication mode network side device, the method further comprises:

sending a session establishment request to the first communication mode network side equipment, wherein the session establishment request indicates that a session mode is SSC1;

receiving a session establishment rejection request of the first communication mode network side equipment, wherein the session establishment rejection request carries a cause value or a session mode SSC3;

and sending a session establishment request again to the first communication mode network side equipment, wherein the session establishment request indicates that the session mode is SSC3.

2. The connection establishing method according to claim 1, wherein the indication information indicates that the first communication mode network and the second communication mode network are independently networked and do not interface with each other.

3. The method according to claim 1, wherein the obtaining the indication information of the first communication mode network side device comprises:

and acquiring the indication information in the process of establishing the first session or attaching the first communication mode network.

4. The connection establishing method according to claim 3, wherein the establishing a first session with the first communication mode network side device, and the obtaining the indication information in the first session establishing process comprises:

sending a session establishment request to the first communication mode network side equipment;

and receiving a session establishment request response of the first communication mode network side equipment, wherein the session establishment request response carries the indication information.

5. The method according to claim 3, wherein acquiring the indication information during the attaching of the first communication mode network comprises:

sending an attachment request to the first communication mode network side equipment;

and receiving an attach request response of the first communication mode network side equipment, wherein the attach request response carries the indication information.

6. The connection establishment method of claim 1, wherein the first session is an SSC3 session.

7. The connection establishing method according to claim 4, wherein before sending the session establishment request to the first communication mode network side device, the method further comprises:

detecting that the signal strength of the first communication mode network is greater than the signal strength of the second communication mode network.

8. The connection establishing method according to claim 1, wherein establishing a transport layer path with a second communication mode network side device before the first session is interrupted comprises:

detecting signal strengths of the first communication mode network and the second communication mode network;

when the signal intensity of the second communication mode network is greater than a first threshold value, establishing a second session with the second communication mode network side equipment, and establishing a transmission layer path between the second communication mode network side equipment and the second communication mode network side equipment;

releasing the first session when the signal strength of the first communication mode network is less than a second threshold, the second threshold being less than the first threshold.

9. The method according to claim 1, wherein the establishing the transport layer path with the second communication mode network side device comprises:

when the transmission layer supports multi-path transmission, establishing a new transmission sub-flow between the second communication mode network side equipment and the transmission layer;

and when the transport layer does not support multipath transmission, establishing a new TCP connection between the second communication mode network side equipment and the second communication mode network side equipment.

10. A connection establishment method is applied to a network side device in a first communication mode and/or a second communication mode, and comprises the following steps:

sending indication information to a terminal in a coverage range, wherein the indication information is used for indicating the terminal to establish a transmission layer path between the terminal and a second communication mode network side device before a first session between the terminal and the first communication mode network side device is interrupted;

the method further comprises the following steps:

receiving a session establishment request of the terminal, wherein the session establishment request indicates that a session mode is SSC1;

sending a session establishment rejection request to the terminal, wherein the session establishment rejection request carries a cause value or a session mode SSC3;

and receiving a session establishment request sent again by the terminal, wherein the session establishment request indicates that the session mode is SSC3.

11. The connection establishing method according to claim 10, wherein the sending the indication information to the terminals within the coverage area comprises:

and sending the indication information to the terminal in a session establishment process between the terminal and the network side equipment or an attachment process of the terminal.

12. The connection establishing method according to claim 11, wherein sending the indication information to the terminal in a session establishment procedure between the terminal and the network-side device comprises:

receiving a session establishment request of the terminal;

and sending a session establishment request response to the terminal, wherein the session establishment request response carries the indication information.

13. The connection establishing method according to claim 11, wherein sending the indication information to the terminal during the terminal's attach procedure comprises:

receiving an attachment request of the terminal;

and sending an attachment request response to the terminal, wherein the attachment request response carries the indication information.

14. A connection set-up device for a terminal, the terminal being located within the coverage of a first communication mode network and/or a second communication mode network, the device comprising a processor and a transceiver,

the processor is used for establishing a first session with a first communication mode network side device;

the transceiver is configured to acquire indication information of the first communication mode network side device, where the indication information is used to indicate that the terminal establishes a transport layer path with a second communication mode network side device before the first session is interrupted;

the processor is further configured to establish a transport layer path with a second communication mode network side device before the first session is interrupted;

the transceiver is further configured to send a session establishment request to the first communication mode network side device, where the session establishment request indicates that a session mode is SSC1; receiving a session establishment rejection request of the first communication mode network side equipment, wherein the session establishment rejection request carries a cause value or a session mode SSC3; and sending a session establishment request again to the first communication mode network side equipment, wherein the session establishment request indicates that the session mode is SSC3.

15. A connection establishment apparatus, characterized in that, a network side device applied to a first communication mode and/or a second communication mode, the apparatus comprises a processor and a transceiver,

the transceiver is used for sending indication information to a terminal in a coverage range, and the indication information is used for indicating the terminal to establish a transmission layer path between the terminal and a second communication mode network side device before a first session between the terminal and the first communication mode network side device is interrupted;

the transceiver is further configured to receive a session establishment request of the terminal, where the session establishment request indicates that a session mode is SSC1; sending a session establishment rejection request to the terminal, wherein the session establishment rejection request carries a cause value or a session mode SSC3; and receiving a session establishment request sent again by the terminal, wherein the session establishment request indicates that the session mode is SSC3.

16. A communication device, comprising: memory, processor and computer program stored on the memory and executable on the processor, which computer program, when executed by the processor, carries out the steps in the connection establishment method according to any one of claims 1 to 13.

17. A computer-readable storage medium, having stored thereon a computer program which, when being executed by a processor, carries out the steps of a method for establishing a connection as claimed in any one of claims 1 to 13.

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