Switching method and equipment

Abstract

The invention provides a switching method and equipment. The method comprises the following steps: a source base station informs a source core network of whether a direct data forwarding path is available or not; the source core network decides to adopt direct data forwarding or indirect data forwarding; the source core network informs the target core network of information of direct data forwarding, indirect data forwarding or impossible data forwarding; the target core network informs the target base station of information of direct data forwarding, indirect data forwarding or impossible data forwarding; and the destination base station allocates channel information of data forwarding.

Description

[0001] This application is a divisional application of the invention patent application with application number 201910245257.6, application date March 28, 2019, and invention name “Switching method and device”. Technical Field

[0002] The present application relates to wireless communication technology, and in particular to a switching method and device. Background Art

[0003] Modern mobile communications are increasingly tending to provide users with high-speed transmission of multimedia services, such as Figure 1 The following is a diagram of the system architecture of the System Architecture Evolution (SAE). User equipment (UE) 101 is a terminal device used to receive data. Evolved Universal Terrestrial Radio Access Network (E-UTRAN) 102 is a radio access network, which includes a macro base station (eNodeB / NodeB) that provides a wireless network interface for UE to access. Mobile management entity (MME) 103 is responsible for managing the mobility context, session context and security information of UE. Serving gateway (SGW) 104 mainly provides user plane functions, and MME 103 and SGW 104 may be in the same physical entity. Packet data network gateway (PGW) 105 is responsible for functions such as billing and lawful interception, and may also be in the same physical entity as SGW 104. Policy and charging rules function entity (PCRF) 106 provides quality of service (QoS) policy and charging criteria. General packet radio service support node (SGSN) 108 is a network node device that provides routing for data transmission in the universal mobile telecommunications system (UMTS). The Home Subscriber Server (HSS) 109 is the home subsystem of the UE and is responsible for protecting user information including the current location of the user equipment, the address of the serving node, user security information, and the packet data context of the user equipment.

[0004] The overall architecture of 5G is as follows Figure 2 As shown. User equipment (UE) 201 is a terminal device used to receive data. Next generation radio access network (NG-RAN) 202 is a radio access network, which includes a base station that provides a wireless network interface for UE to access. The base station here can be a gNB or an eNB connected to 5GC. The eNB connected to 5GC can also be called ng-eNB. The access control and mobility management function entity (AMF) 203 is responsible for managing the mobility context and security information of the UE. The user plane function entity (UPF) 204 mainly provides user plane functions. The session management function entity SMF205 is responsible for session management. The data network (DN) 206 includes services such as operators, Internet access and third-party services.

[0005] The interface between NG-RAN and AMF is NG-C or N2, and the interface between NG-RAN and UPF is NG-U or N3.

[0006] In the next generation network deployment, there are scenarios where LTE and 5G networks coexist. When the UE moves at the boundary between E-UTRAN and NG-RAN, in order to ensure service continuity, the technology of switching between different radio access technologies (inter-RAT) is still needed. In the EPS system, there is the concept of EPS bearer, but in the 5GS system, there is no concept of EPS bearer. There are two different solutions for data forwarding when switching between the two systems.

[0007] One solution is to use one data channel per PDU session between the NG-RAN node and the UPF. For handover from 5G to 4G, the UPF sends the data streams with different Qos flows received from each PDU session channel to the corresponding E-RAB channel to the SGW, which forwards the data to the eNB. For handover from 4G to 5G, the UPF sends the data received from each E-RAB channel to the corresponding PDU session channel, which is then sent to the NG-RAN node by the UPF.

[0008] Another solution is to establish a data channel for each E-RAB between the NG-RAN node and the UPF, so that data forwarding between the NG-RAN node and the eNB is carried out through each E-RAB channel between the NG-RAN and the UPF, between the UPF and the SGW, and between the SGW and the eNB. This data forwarding method can also forward data directly between the NG-RAN node and the eNB without going through the core network.

[0009] If these two data forwarding methods are adopted at the same time, how to ensure the coexistence and interoperability of the two data forwarding methods in the network has not been discussed yet.

[0010] During the handover process between EPS and 5GS, the allocation of data forwarding channels and the execution of data forwarding involve NG-RAN nodes, SMF, UPF, SGW and eNB. If two different data forwarding methods exist at the same time, the interoperability between different nodes is a problem that needs to be solved, especially when the above devices come from different manufacturers. If one device supports different data methods than another, data forwarding will not work properly. Summary of the invention

[0011] In view of the shortcomings of the existing methods, the present application proposes a method and device for supporting switching.

[0012] In a first aspect, an embodiment of the present application provides a method for supporting switching, comprising the steps of: The source base station informs the source core network whether the direct data forwarding path is available; The source core network decides whether to use direct data forwarding or indirect data forwarding; The source core network notifies the destination core network of the information of direct data forwarding, indirect data forwarding or impossibility of data forwarding; The destination core network notifies the destination base station of the information of direct data forwarding, indirect data forwarding or impossibility of data forwarding; The destination base station allocates channel information for data forwarding.

[0013] Specifically, the destination base station allocates the corresponding data forwarding channel according to whether it is direct data forwarding or indirect data forwarding. If it is direct data forwarding, for the QoS flow that the destination base station accepts data forwarding or the E-RAB that accepts data forwarding, the destination base station allocates downlink data forwarding channel information to the corresponding E-RAB. If it is indirect data forwarding, for the QoS flow that the destination base station accepts data forwarding, the destination base station allocates downlink data forwarding channel information to the PDU session.

[0014] Specifically, the method further comprises the step that the destination base station sends the allocated data forwarding channel information to the destination core network.

[0015] Another embodiment of the present invention provides a method for supporting switching, comprising the following steps: The source base station sends a source base station identifier to the source core network; The source core network sends the source base station identifier to the destination core network; The destination core network sends the source base station identifier to the destination base station; The destination base station determines whether direct data forwarding is available, and the destination base station allocates a corresponding data forwarding channel.

[0016] Specifically, the method further comprises the step that the destination base station sends information that direct data forwarding is available to the destination core network.

[0017] Specifically, the method further comprises the step that the destination core network sends information that direct data forwarding is available to the source core network.

[0018] Another embodiment of the present invention provides a method for supporting switching, comprising the following steps: The source base station sends the data forwarding mode it supports to the source core network; The source core network allocates data forwarding channel information according to the data forwarding mode supported by the source base station; Specifically, the data forwarding mode includes data forwarding of a PDU session channel and / or data forwarding of an E-RAB channel.

[0019] Another embodiment of the present invention provides a method for supporting switching, comprising the following steps: UPF sends the data forwarding methods it supports to SMF; SMF sends the data forwarding method supported by UPF to AMF; AMF sends the data forwarding mode supported by UPF to the destination NG-RAN node The NG-RAN node allocates data forwarding channel information according to the data forwarding mode supported by the UPF; Specifically, the data forwarding mode includes data forwarding of a PDU session channel and / or data forwarding of an E-RAB channel.

[0020] The method for supporting switching in the present invention can solve the above-mentioned problems, thereby completely solving the problem of coexistence of different data forwarding methods when UE moves between LTE and 5G systems, avoiding data loss, ensuring business continuity, ensuring interoperability between equipment from different manufacturers, and reducing operator configuration. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which: Figure 1 The system architecture diagram for System Architecture Evolution (SAE); Figure 2 This is a schematic diagram of the initial overall architecture of 5G; Figure 3 A schematic diagram of method 1 for supporting switching according to the present invention; Figure 4 A schematic diagram of an embodiment 1 of the present invention supporting a switching method 1; Figure 5 It is a schematic diagram of Embodiment 2 of the present invention supporting the switching method 1; Figure 6 A schematic diagram of the second switching method supported by the present invention; Figure 7 A schematic diagram of the third switching method supported by the present invention; Figure 8 A schematic diagram of a fourth switching method supported by the present invention; Fig. 9 A schematic diagram of a fifth switching method supported by the present invention; Fig.10 It is a schematic diagram of the sixth switching method supported by the present invention. DETAILED DESCRIPTION The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be interpreted as limiting the present application.

[0022] Those skilled in the art will appreciate that, unless expressly stated otherwise, the singular forms "a", "an", "" and "the" used herein may also include the plural forms. It should be further understood that the term "comprising" used in the specification of the present application refers to the presence of features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that when we refer to an element as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other elements, or there may be intermediate elements. In addition, "connected" or "coupled" as used herein may include wireless connections or wireless couplings. The term "and / or" as used herein includes all or any unit and all combinations of one or more associated listed items.

[0023] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as generally understood by those skilled in the art to which this application belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless specifically defined as here.

[0024] It will be understood by those skilled in the art that the "terminal" and "terminal device" used herein include both devices with wireless signal receivers, which are devices with only wireless signal receivers without transmission capabilities, and devices with receiving and transmitting hardware, which are devices with receiving and transmitting hardware capable of two-way communication on a two-way communication link. Such devices may include: cellular or other communication devices, which have a single-line display or a multi-line display or a cellular or other communication device without a multi-line display; PCS (Personal Communications Service), which may combine voice, data processing, fax and / or data communication capabilities; PDA (Personal Digital Assistant), which may include a radio frequency receiver, a pager, Internet / intranet access, a web browser, a notepad, a calendar and / or a GPS (Global Positioning System) receiver; conventional laptop and / or palmtop computers or other devices, which have and / or include a conventional laptop and / or palmtop computer or other device with and / or including a radio frequency receiver. The "terminal" and "terminal device" used here can be portable, transportable, installed in a vehicle (air, sea and / or land), or suitable and / or configured to operate locally, and / or in a distributed form, at any other location on the earth and / or in space. The "terminal" and "terminal device" used here can also be a communication terminal, an Internet terminal, a music / video playback terminal, such as a PDA, a MID (Mobile Internet Device) and / or a mobile phone with music / video playback function, or a smart TV, a set-top box and other devices.

[0025] During the UE switching process between EPS and 5GS, there are three ways for the two data forwarding methods to coexist: Method 1: Method 1 is used for indirect data forwarding, that is, one data channel per PDU session is used between the NG-RAN node and the UPF. Method 2 is used for direct data forwarding, that is, direct data forwarding is performed between the NG-RAN node and the eNB through the E-RAB channel.

[0026] Method 2: The standard does not restrict when to use which data forwarding method. The specific data forwarding method supported depends on the implementation of the equipment manufacturer.

[0027] Method 3: Both data forwarding methods must be supported.

[0028] Direct data forwarding can only be performed when there is a direct interface or a secure connection between the eNB and the NG-RAN node. Corresponding to the above method 1, during the switching process from EPS to 5GS, if it is direct data forwarding, the target NG-RAN node needs to allocate data forwarding channel information for the E-RAB corresponding to the Qos flow that receives data forwarding and include it in the switching request confirmation message. If it is indirect data forwarding, the target NG-RAN node needs to allocate data forwarding channel information for the PDU session to which the Qos flow that receives data forwarding belongs and include it in the switching request confirmation message. However, in the prior art, the target NG-RAN node does not know whether the eNB and the NG-RAN node have a direct interface or a secure connection.

[0029] During the handover process from EPS to 5GS, if it is direct data forwarding, AMF directly sends the channel corresponding to each E-RAB allocated by the target NG-RAN node to MME, and then sends it to the source eNB through MME. If it is indirect data forwarding, AMF needs to send the data forwarding channel information corresponding to each PDU session allocated by the target NG-RAN node to UPF through SMF, and SMF or UPF allocates the data forwarding channel from SGW to UPF corresponding to each E-RAB. It can be seen that the behavior of UPF is different for the two data forwarding methods, but UPF does not know whether the eNB and NG-RAN nodes have a direct interface or a secure connection, so UPF does not know whether to allocate a data forwarding channel.

[0030] The method of the present invention supporting switching is as follows Figure 3 As shown. The method solves the above two problems, so that data forwarding in the switching process between different systems is successfully executed. Detailed description of steps not related to the present invention is omitted here. The method includes the steps of: Step 301, the source base station informs the source core network whether the direct data forwarding path is available. The source base station can determine whether the direct data forwarding path is available based on whether there is a direct interface or a secure interface between the source base station and the destination base station. The source base station can also consider other factors to determine whether direct data forwarding is available without affecting the main content of the present invention. The source base station informs the source core network whether the direct data forwarding path is available through a switching demand message.

[0031] The source base station proposes downlink data forwarding. The source base station proposes downlink data forwarding to the E-RAB.

[0032] Step 302: The source core network determines direct data forwarding or indirect data forwarding. The core network determines direct data forwarding or indirect data forwarding based on information received from the source base station about whether the direct data forwarding path is available. If direct data forwarding is not available, the source core network determines whether indirect data forwarding is feasible. If both direct data forwarding and indirect data forwarding are not feasible, data forwarding is impossible.

[0033] Step 303: The source core network informs the destination core network of the information of direct data forwarding and indirect data forwarding. The source core network may also inform the destination core network of the information that data forwarding is not feasible. Step 304: The destination core network informs the destination base station of the direct data forwarding, indirect data forwarding or data forwarding impossibility. The destination core network informs the destination base station of the direct data forwarding, indirect data forwarding or data forwarding impossibility through a handover request message.

[0034] Step 305, the destination base station allocates channel information for data forwarding. If the destination base station accepts the downlink data forwarding proposed by the source base station, the destination base station allocates channel information for downlink data forwarding. The destination base station allocates corresponding data forwarding channels according to whether it is direct data forwarding or indirect data forwarding. If it is direct data forwarding, for the Qos flow that the destination base station accepts data forwarding or the E-RAB that accepts data forwarding, the destination base station allocates downlink data forwarding channel information to the corresponding E-RAB. If it is indirect data forwarding, for the Qos flow that the destination base station accepts data forwarding, the destination base station allocates downlink data forwarding channel information to the PDU session. If data forwarding is not feasible, the destination base station does not need to allocate data forwarding channel information.

[0035] The destination base station knows whether to forward data directly or indirectly according to the switching request message received from the destination core network.

[0036] Step 306: The destination base station sends the allocated data forwarding channel information to the destination core network. For different data forwarding methods in step 305, the data forwarding channel information may be for each PDU session or for each E-RAB. The data forwarding channel information includes downlink data forwarding channel information and / or uplink data forwarding channel information.

[0037] Step 307: For direct data forwarding, the destination core network sends the data forwarding channel information allocated by the destination base station to the source core network. For indirect data forwarding, the destination core network allocates the data forwarding channel information between the source core network and the destination core network and sends it to the source core network.

[0038] Step 308: For direct data forwarding, the source core network sends the data forwarding channel information received from the destination core network to the source base station. For indirect data forwarding, the source core network allocates data forwarding channel information between the source base station and the source core network and sends it to the source base station.

[0039] The source base station forwards data according to the received data forwarding channel information. The destination base station receives the forwarded data. The destination base station first sends the forwarded data to the UE, and then sends the new data received from the destination core network.

[0040] So far, the description of switching method 1 of the present invention is completed. This method can completely solve the problem of coexistence of different data forwarding methods when the UE moves between the EPS and 5GS systems, avoid data loss, ensure business continuity, ensure interoperability between equipment from different manufacturers, and reduce the configuration of operators.

[0041] The present invention supports the switching method 1 as follows: Figure 4 As shown. In this method, SMF or AMF sends information about direct data forwarding or indirect data forwarding to the destination base station, so that the destination base station decides how to allocate data forwarding channel information. This method solves the above two problems, so that data forwarding during the switching process is successfully executed, and the various entities in the network coordinate their work to ensure the successful data forwarding. Detailed descriptions of steps not related to the present invention are omitted here. This embodiment is used for switching from EPS to 5GS, and includes the steps of: Step 400: E-UTRAN decides to handover the UE to NG-RAN.

[0042] The E-UTRAN here can be an eNB connected to the EPC. The NG-RAN can be a gNB or an eNB connected to the 5GC or a centralized unit CU in the gNB. The eNB connected to the 5GC can also be called an ng-eNB.

[0043] The user plane path before switching is PGW-U+UPF (UPF has PGW user plane function, hereinafter referred to as UPF), SGW to E-UTRAN. SGW needs to support the interface with PGW-U+UPF. UE has one or more PDU sessions in progress. Each PDU session contains one or more EPS bearers. During the PDU session establishment or EPS bearer establishment process, the EPS bearer is allocated QoS information and / or QoS flow identifier of the mapped QoS flow. The default EPS bearer is mapped to the non-guaranteed service rate (non-GBR) QoS flow. The QoS information and / or QoS flow identifier of the QoS flow mapped by the EPS bearer can be allocated by the PCC or PGW control plane function. In order to support switching between different systems, the PGW control plane function can also have SMF function. In the scenario of PCC deployment, the policy control and charging function (PCRF) provides the QoS and / or QoS flow identifier of the QoS flow mapped by the EPS bearer to the SMF. In order to support switching between different systems, there is also a policy control function (PCF) on the PCRF. SMF sends the QoS and / or QoS flow identifier of the QoS flow mapped by the EPS bearer to the UE through the MME, for example, through the non-access layer message PDN connection establishment message to the UE. During the PDU session establishment or EPS bearer establishment process, SMF can also send the QoS and / or QoS flow identifier of the QoS flow mapped by the EPS bearer to the E-UTRAN through the MME. E-UTRAN can send the mapping information to the UE through an RRC message. The E-RAB and EPS bearer identifiers are the same or have a one-to-one correspondence. In the core network, it is an EPS bearer, and in the access network, it is called an E-RAB. The E-RAB identifier and the EPS bearer identifier are the same or have a one-to-one correspondence. In the core network, it is an EPS bearer identifier, and in the access network, it is called an E-RAB identifier.

[0044] Step 401, E-UTRAN sends a handover request message to MME. The message includes the identifier of the target NG-RAN node and the transparent transmitter from the source to the target. The message also includes the identifier information indicating the AMF to which the target NG-RAN node is connected. The identifier information may be a tracking area identifier, a network slice identifier, an AMF pool identifier, or an AMF identifier, etc.

[0045] The message contains information that a direct data forwarding path is available.

[0046] The source-to-destination transparent transmitter includes a PDU session identifier, an identifier of the Qos flow in the PDU session, and downlink data forwarding proposed for the Qos flow. The eNB obtains the PDU session identifier corresponding to the EPS bearer and / or the Qos flow identifier in the PDU session through the PDN connection establishment process or through the switching process. The Qos information of the mapped Qos flow may also be obtained. The eNB decides whether to propose data forwarding based on the mapping of the Qos flow from the E-RAB to the PDU session or from the E-RAB to the PDU session and the Qos information. The eNB may consider other factors such as whether there is buffered data to make a decision without affecting the main content of the present invention.

[0047] Step 402: MME sends a forward relocation request message to AMF. MME selects and finds AMF according to the identification information of the AMF to which the destination NG-RAN node is connected contained in the handover requirement message. The message includes the identification of the destination NG-RAN node, the source-to-destination transparent transmitter and UE context information. The UE context information includes UE mobility management MM context information and session management context. The message includes the type of handover.

[0048] The MME sends a direct forwarding indication to the AMF. The direct forwarding indication can indicate direct data forwarding or indirect data forwarding. If the MME receives a message from the source E-UTRAN that direct data forwarding is not feasible, the MME decides whether indirect data forwarding is feasible. The MME informs the AMF of whether direct data forwarding is indirect data forwarding. The MME can also inform the AMF of the information that data forwarding is not feasible, where the data forwarding is not feasible means that both direct data forwarding and indirect data forwarding are not feasible. Alternatively, the MME can also inform the AMF of the information that direct data forwarding is available.

[0049] In step 403a, the AMF sends a Create Session (SM) Context Request message to the SMF. The AMF converts the received EPS UE context into a 5GS UE context. The AMF can also exchange with the PCRF to obtain the converted 5GS UE context. The AMF selects the SMF that serves the UE.

[0050] According to the information received in the forwarding relocation request message, the AMF knows that the handover is between different systems, and the AMF requests the SMF to provide the SM context. The AMF sends the message to each SMF serving the UE.

[0051] AMF sends a direct forwarding indication to SMF, which may indicate direct data forwarding or indirect data forwarding. AMF informs SMF of the available information of direct data forwarding or indirect data forwarding.

[0052] Step 404, SMF initiates the N4 session modification process with UPF.

[0053] Step 403b, SMF sends a create session context response message to AMF. The message contains the SM context of the UE. The SM context also contains the mapping relationship between the EPS bearer and the QoS flow in the PDU session. If the SMF has a mapped EPS bearer context when the AMF requests the SM context, the SMF always feeds back the mapped EPS bearer context to the AMF at the same time. Or the SMF sends the mapped EPS bearer context to the AMF only when the AMF requests the mapped EPS context at the same time.

[0054] The 5GS UE context contains the QoS information in the 5G system. The QoS information in the 5G system contains QoS rules and / or QoS profiles. AMF can map EPS QoS information into 5G QoS information, or AMF interacts with the 5G Policy Control Function (5G-PCF) to derive 5G QoS information.

[0055] SMF determines that direct data forwarding, indirect data forwarding or data forwarding is not feasible. If the direct forwarding received by SMF indicates that direct data forwarding is feasible, SMF may decide to use direct data forwarding. If the direct forwarding received by SMF indicates indirect data forwarding and indirect data forwarding is feasible, SMF decides to use indirect data forwarding. If the direct forwarding received by SMF indicates indirect data forwarding but there is no indirect data forwarding connection, SMF determines that data forwarding is not possible. SMF includes information that direct data forwarding, indirect data forwarding or data forwarding is not feasible in the N2 session management (SM) information container. The direct data forwarding information may be information that direct data forwarding is available. The data forwarding is not feasible means that indirect data forwarding is not feasible or both direct and indirect data forwarding are not feasible. Step 405, AMF sends a switching request message to NG-RAN. The message contains information about the PDU session to be established. The information about the PDU session includes session identifier, session QoS information, QoS flow information, uplink channel information for each session, and / or a transparent transmitter from source to destination. The message contains the type of switching.

[0056] The message includes information that direct data forwarding, indirect data forwarding or data forwarding is not possible. The information may be included in an N2 SM information container. The direct data forwarding information may be information that direct data forwarding is available. The data forwarding not being feasible means that indirect data forwarding is not feasible or both direct and indirect data forwarding are not feasible.

[0057] The message may also include a mapping relationship between the Qos flow in the PDU session and the EPS bearer, that is, an E-RAB identifier mapped by the Qos flow and / or mapped Qos information.

[0058] Step 406: NG-RAN sends a handover request confirmation message to AMF. The message includes one or more of the following information: The transparent transmitter from the destination to the source may also include a mapping relationship between the Qos flow in the PDU session and the EPS bearer, that is, the EPS bearer identifier mapped by the Qos flow and / or the mapped Qos information.

[0059] The NG-RAN accepts the PDU session information list established. The PDU session information list includes the PDU session identifier, the downlink channel information of the NG3 interface used for the PDU session, the Qos flow information accepted by the PDU session, and the Qos flow information not accepted.

[0060] If it is direct data forwarding, for the QoS flow that NG-RAN accepts data forwarding or the E-RAB that accepts data forwarding, NG-RAN allocates downlink data forwarding channel information to the corresponding E-RAB, and includes the E-RAB identifier and the downlink channel information corresponding to the E-RAB allocated by NG-RAN in the handover request confirmation message. If it is indirect data forwarding, for the QoS flow that NG-RAN accepts data forwarding, NG-RAN allocates downlink data forwarding channel information to the PDU session to which it belongs, and includes the PDU session identifier and the downlink channel information corresponding to the PDU session allocated by NG-RAN in the handover request confirmation message, and may also include a list of QoS flows that accept data forwarding. If data forwarding is not feasible, NG-RAN does not need to allocate data forwarding channel information.

[0061] The NG-RAN does not accept the established PDU session information list. The PDU session information list includes the PDU session identifier and the reason for not accepting.

[0062] In step 407, AMF sends an update SM context request message to SMF. If channel information for data forwarding is received from NG-RAN, AMF sends the data forwarding channel information received from NG-RAN to SMF. AMF sends the channel information for data forwarding received from NG-RAN to SMF. AMF sends information on direct data forwarding or indirect data forwarding to SMF. AMF can inform SMF of direct data forwarding or indirect data forwarding in an explicit manner. AMF can also inform SMF in an implicit manner, that is, if SMF receives data forwarding channel information corresponding to each E-RAB, it is direct data forwarding, if it receives data forwarding channel information corresponding to each PDU session, it is indirect data forwarding, and if there is no data forwarding channel information, data forwarding is not feasible or data forwarding is not accepted by the destination base station. The message includes the PDU session to which the EPS bearer belongs. The message may also include a mapping relationship between the EPS bearer and the Qos flow in the PDU session.

[0063] Step 408, SMF initiates the session modification process between SMF and UPF. If SMF receives the data forwarding channel information of each PDU session, SMF sends the NG3 interface downlink data forwarding channel information allocated by NG-RAN to UPF through the N4 session modification process, and the data forwarding channel information is for each PDU session. SMF allocates data forwarding channel information between SGW and UPF, or UPF allocates channel information for data forwarding between SGW and UPF and sends it to SMF, and the data forwarding channel information is for each E-RAB. The N4 session modification message includes the PDU session to which the EPS bearer belongs. The N4 session establishment or N4 session modification message may also include the mapping relationship between the EPS bearer and the Qos flow in the PDU session. If SMF receives the data forwarding channel information of each E-RAB, it is direct data forwarding, and SMF or UPF does not need to allocate data forwarding channel information.

[0064] Step 409, SMF sends an update SM context response message to AMF. SMF sends the channel information used for data forwarding to AMF. For direct data forwarding, SMF sends the channel information corresponding to each E-RAB received from AMF to AMF, and the channel information corresponding to each E-RAB is allocated by the target NG-RAN. For indirect data forwarding, SMF sends the channel information of each E-RAB allocated by SMF or UPF to AMF, and the channel information is used for data forwarding between SGW and UPF.

[0065] Step 410, AMF sends a forwarding relocation response message to MME. The message contains data forwarding channel information. For direct data forwarding, the channel information is allocated by the destination NG-RAN. For indirect data forwarding, the channel information is the channel information received from SMF for data forwarding between SGW and UPF. The message contains a transparent transmitter from the destination to the source.

[0066] Step 411, if the MME receives the channel information for data forwarding, for indirect data forwarding, the MME sends a request message for creating an indirect data forwarding channel to the SGW. The message is used to send the channel information for data forwarding between the SGW and the UPF to the SGW. The SGW sends a response message for creating an indirect data forwarding channel to the MME. The message contains the uplink channel information allocated by the SGW for S1 interface data forwarding. For direct data forwarding, this step does not need to be performed. The MME knows whether to forward data directly or indirectly based on the information on the available direct data forwarding path received from the source base station, as described in step 402.

[0067] Step 412: MME sends a handover command message to E-UTRAN, wherein the message includes a transparent transmission from the destination to the source, and the handover type.

[0068] The message includes data forwarding channel information. For indirect data forwarding, the channel information is allocated by the SGW. For direct data forwarding, the channel information is allocated by the destination NG-RAN.

[0069] Step 413: E-UTRAN sends a handover command message to the UE.

[0070] The message may also include a mapping relationship between the Qos flow and the EPS bearer in the PDU session, that is, the EPS bearer identifier mapped by the Qos flow and / or the mapped Qos information.

[0071] E-UTRAN forwards data. For the E-RAB that receives the data forwarding channel, it means that the destination base station has accepted the data forwarding, and E-UTRAN forwards the data to the corresponding channel. For direct data forwarding, the destination NG-RAN directly receives the data forwarded by E-UTRAN. For indirect data forwarding, SGW receives the data forwarded by E-UTRAN. SGW forwards the data to UPF. SGW forwards the data to UPF on the corresponding channel for each EPS bearer that requires data forwarding. UPF forwards the data to NG-RAN. UPF sends the data belonging to the same PDU session received from the SGW corresponding to the channel of each EPS bearer to NG-RAN through the PDU session channel, that is, UPF maps multiple channels to one channel. UPF forwards data to NG-RAN according to the session transmission method in 5GS. For example, each PDU session sends downlink data through several Qos flows, and how to set the Qos flow header. UPF adds the Qos flow identifier (QFI) to the header of the data packet forwarded to the destination NG-RAN.

[0072] NG-RAN receives the forwarded data from the PDU session channel, and NG-RAN sends the received data to the UE in the existing manner. NG-RAN receives the forwarded data from the E-RAB channel, and NG-RAN does not need to process the SDAP layer, and directly sends the data to the PDCP layer of the corresponding DRB. Based on the mapping relationship between the E-RAB ID(s) and the Qos Flow ID(s) received in the handover request message, NG-RAN knows the DRB corresponding to the E-RAB, and thus directly sends the received forwarded data to the PDCP entity of the corresponding DRB. NG-RAN first sends the forwarded data to the UE, and then sends the data received from the new NG-U to the UE.

[0073] During the PDU session establishment or EPS bearer establishment process, the UE receives the QoS information and / or QoS flow information of the QoS flow mapped by the EPS bearer from the network. The UE associates the correspondence between the ongoing EPS bearer and the QoS flow contained in the handover command message. For EPS bearers that do not have a corresponding QoS flow, the UE can delete them.

[0074] Or the UE obtains the mapping relationship between the QoS flow in the PDU session and the EPS bearer from the handover command message. The UE associates the ongoing EPS bearer with the corresponding relationship between the QoS flow contained in the handover command message. For the EPS bearer without corresponding QoS flow, the UE can delete it.

[0075] Step 414: The UE sends a handover complete message to the NG-RAN.

[0076] Step 415: NG-RAN sends a handover notification message to AMF, wherein the message includes channel information allocated by NG-RAN for downlink data transmission.

[0077] Step 416, AMF sends an update SM context request message to SMF.

[0078] Step 417: SMF sends an N4 session modification message to UPF. UPF sends an N4 session modification response message to SMF.

[0079] AMF sends the channel information of downlink data transmission allocated by NG-RAN to UPF through AMF.

[0080] Step 418, SMF sends an update SMF context response message to AMF.

[0081] So far, the description of the first embodiment of the switching method of the present invention is completed. This method can completely solve the problem of coexistence of different data forwarding methods when the UE moves between the LTE and 5G systems, avoid data loss, ensure business continuity, ensure interoperability between equipment from different manufacturers, and reduce the configuration of operators.

[0082] The present invention supports the second embodiment of the switching method 1 as follows Figure 5 As shown. The method solves the above two problems, so that the data forwarding in the switching process is successfully executed, and the different entities in the network coordinate work to ensure the successful data forwarding. Detailed descriptions of steps not related to the present invention are omitted here. This embodiment is used for switching from 5GS to EPS, and includes the steps of: Step 501, NG-RAN decides to hand over the UE to E-UTRAN.

[0083] Here, E-UTRAN can be an eNB connected to EPC. NG-RAN can be a gNB or an eNB connected to 5GC or a centralized unit CU in a gNB.

[0084] The user plane path before handover is from UPF to NG-RAN. SGW needs to support the interface with UPF. UPF can include the functions of PGW user plane and perform the functions of user plane anchor point during handover between different RATs.

[0085] The UE has one or more PDU sessions in progress. Each PDU session contains one or more QoS flows. During the PDU session establishment or guaranteed service rate (GBR) QoS flow establishment process, the mapped EPS QoS information and / or EPS bearer identifier are allocated to the QoS flow. The non-guaranteed service rate (non-GBR) QoS flow is mapped to the default EPS bearer. The GBR QoS flow is mapped to the EPS dedicated bearer. The EPS QoS information mapped by the QoS flow can be allocated by the PCC or SMF. The EPS bearer identifier mapped by the QoS flow can be allocated by the SMF or AMF. In order to support switching between different systems, the SMF can also have the function of the PGW control plane. In the scenario of PCC deployment, the policy control function (PCF) provides the EPS QoS mapped by the QoS flow to the SMF. In order to support switching between different systems, the PCF can also have a policy control and charging function (PCRF). The SMF sends the EPS QoS information and / or EPS bearer identifier mapped by the QoS flow to the UE through the AMF, for example, through the non-access layer message PDU session establishment message to the UE. During the PDU session establishment or guaranteed service rate (GBR) QoS flow establishment process, SMF can also send EPS QoS information and / or E-RAB identifier mapped by QoS flow to NG-RAN through AMF. AMF sends EPS QoS information and / or E-RAB identifier mapped by QoS flow to NG-RAN through initial context establishment request message or PDU session resource establishment request message. NG-RAN can send EPS QoS information and / or E-RAB identifier mapped by QoS flow to UE through RRC message. E-RAB and EPS bearer identifiers are the same or have one-to-one correspondence. In the core network, it is EPS bearer, and in the access network, it is called E-RAB. The E-RAB identifier and EPS bearer identifier are the same or have one-to-one correspondence. In the core network, it is EPS bearer identifier, and in the access network, it is called E-RAB identifier.

[0086] In step 502, NG-RAN sends a switching request message to AMF. The message includes the identifier of the target eNB and the transparent transmitter from the source to the target. The transparent transmitter from the source to the target includes the E-RAB identifier and the downlink data forwarding proposed for this E-RAB. NG-RAN obtains the EPS bearer identifier mapped by the Qos flow in the PDU session through the PDU session establishment process or through the switching process. The mapped EPS Qos information may also be obtained. NG-RAN decides whether to propose data forwarding based on the mapping of the Qos flow to the E-RAB and the Qos information. NG-RAN can consider other factors such as whether there is buffered data to make a decision without affecting the main content of the present invention. The message includes information that a direct data forwarding path is available.

[0087] The message also includes identification information indicating the MME to which the target eNB is connected. The identification information may be a tracking area identification or an MME identification.

[0088] The message also contains the type of handover.

[0089] AMF decides whether direct data forwarding or indirect data forwarding is available. If AMF does not receive information from the source NG-RAN that a direct data forwarding path is available, AMF decides whether indirect data forwarding is feasible. If direct data forwarding is feasible, direct data forwarding is used.

[0090] Step 503a, AMF sends a session management SM context request message to SMF. Based on the information received in the switching requirement message, AMF knows that the switching is between different systems, and AMF requests SMF to provide SM context. AMF can also request EPS bearer context. AMF sends the message to each SMF serving the UE. AMF sends a direct forwarding indication or information that a direct data forwarding path is available to SMF. The direct forwarding indication can indicate direct data forwarding or indirect data forwarding. . AMF informs SMF whether direct data forwarding or indirect data forwarding is available. SMF saves the received information.

[0091] Step 503b, SMF sends an N4 session modification request message to UPF. The message includes information that a direct forwarding indication or a direct data forwarding path is available. The direct forwarding indication may indicate direct data forwarding or indirect data forwarding. UPF saves information on whether the direct forwarding indication or direct data forwarding is feasible. UPF sends an N4 session modification response message to SMF.

[0092] Step 503c, SMF sends an SM context response message to AMF. The message contains the SM context of the UE. The SM context also contains the mapped EPS bearer context, such as the EPS bearer identifier and / or EPS QoS information. If there is a mapped EPS bearer context when AMF requests the SM context, SMF always feeds back the mapped EPS bearer context to AMF at the same time. Or when AMF requests the SM context from SMF, it also indicates the requested mapped EPS bearer context. SMF sends the mapped EPS bearer context to AMF only when AMF requests the mapped EPS context at the same time.

[0093] The SMF decides that direct data forwarding, indirect data forwarding, or data forwarding is not feasible. If the SMF receives that a direct data forwarding path is available, the SMF may decide to use direct data forwarding. If the SMF does not receive that a direct data forwarding path is available, the SMF decides whether indirect data forwarding is feasible. If indirect data forwarding is feasible, the SMF decides to use indirect data forwarding. If the SMF does not receive that a direct data forwarding path is available and there is no indirect data forwarding connection, the SMF decides that data forwarding is not possible.

[0094] The SMF sends information about direct data forwarding, indirect data forwarding or data forwarding being unfeasible to the AMF. The direct data forwarding information may be information about direct data forwarding being available. The unfeasible data forwarding means that indirect data forwarding is unfeasible or both direct and indirect data forwarding are unfeasible.

[0095] Step 504, AMF sends a forward relocation request message to MME. AMF selects and finds MME according to the identification information of the MME to which the target eNB is connected contained in the handover requirement message. The identification information of the MME to which the target eNB is connected may be TAI. The message includes the identification of the target eNB, the source-to-target transparent transmitter and the mapped EPS UE context information. The mapped EPS UE context information includes UE mobility management MM context information and session SM context information.

[0096] The AMF sends a direct forwarding indication to the MME.

[0097] If the AMF does not receive information from the source NG-RAN that a direct data forwarding path is available, the AMF determines whether indirect data forwarding is feasible. If direct data forwarding is feasible, direct data forwarding is used. If direct data forwarding is not feasible, the AMF determines whether indirect data forwarding is feasible. The AMF knows whether indirect data forwarding is feasible based on the information received from the SMF. The AMF knows whether indirect data forwarding is feasible based on the information received from the SMF that direct data forwarding, indirect data forwarding, or data forwarding is not feasible. The AMF informs the MME whether direct data forwarding or indirect data forwarding is feasible. The AMF can also inform the MME that data forwarding is not feasible, where the data forwarding is not feasible means that both direct data forwarding and indirect data forwarding are not feasible or indirect data forwarding is not feasible.

[0098] Step 505: MME sends a create session request message to SGW, wherein the message includes EPS bearer context information.

[0099] Step 506: The SGW sends a create session response message to the MME, wherein the message includes the channel information of the S1 interface allocated by the SGW for uplink data transmission.

[0100] In step 507, the MME sends a switching request message to the E-UTRAN. The message includes a transparent transmitter from the source to the destination and an E-EAB context. The E-RAB context includes the E-RAB to be established and the uplink channel information of the S1 interface allocated by the SGW. The E-RAB context includes information on whether data forwarding is feasible. The message includes a switching type, and the specific content is the same as in step 902, which will not be repeated here. The message includes information that data forwarding is impossible. If the MME receives information on indirect data forwarding from the AMF (for example, a direct data forwarding indication indicates indirect data forwarding) but indirect data forwarding is not feasible, the MME determines that data forwarding is impossible. If the MME receives a direct data forwarding indication from the AMF indicating direct data forwarding or the MME receives from the AMF that a direct data forwarding path is available, data forwarding is feasible.

[0101] Step 508, E-UTRAN sends a handover request confirmation message to MME. The message includes a list of established E-RABs and a list of failed established E-RABs, and a transparent transmitter from the destination to the source. For the established RAB, it also includes the channel information for downlink data transmission on the S1 interface. For the established E-RAB, if the source eNB proposes downlink data forwarding, data forwarding is feasible, and the target eNB accepts downlink data forwarding, the target eNB includes the data forwarding channel information allocated by E-UTRAN for each E-RAB that needs downlink data forwarding.

[0102] Step 509, MME requests SGW to create an indirect data forwarding channel. This step is performed only when indirect data forwarding needs to be performed. If MME receives indirect data forwarding information from AMF and indirect data forwarding is feasible, MME knows that it is indirect data forwarding. If MME receives downlink channel information for data forwarding from E-UTRAN, MME requests SGW to create an indirect data forwarding channel. MME sends the transport layer address and TEID assigned by eNB for data forwarding to SGW. The transport layer address and TEID correspond to each E-RAB.

[0103] SGW sends an indirect data forwarding channel creation response message to MME. The message includes information allocated by SGW for data forwarding between SGW and UPF. The information used for data forwarding between SGW and UPF includes E-RAB identification and channel information used by the E-RAB for data forwarding. The channel information includes the transport layer address and TEID allocated by SGW. SGW allocates downlink data forwarding channel information to the E-RAB that needs downlink data forwarding. SGW allocates uplink data forwarding channel information to the E-RAB that needs uplink data forwarding. The data forwarding channel information included in the E-RAB information may include uplink and / or downlink data forwarding channel information.

[0104] When indirect data forwarding is feasible, step 509 is performed.

[0105] Step 510, MME sends a forwarding relocation response message to AMF. The message includes channel information for data forwarding. For direct data forwarding, the data forwarding channel information is received by MME from the destination base station. For indirect data forwarding, the channel information is the SGW allocation received by MME from SGW. The channel information is for each EPS bearer. The data forwarding channel information may include downlink and / or uplink data forwarding channel information. The message includes a transparent transmitter from the destination to the source.

[0106] MME directly sends the E-RAB information to AMF, which then converts it.

[0107] Step 511, AMF sends an update SM context request message to SMF. AMF requests SMF to create a data forwarding channel. For indirect data forwarding, AMF requests SMF to create a data forwarding channel. The message contains PDU session information. The PDU session information contains the PDU session identifier, the QoS flow information contained in the PDU session, how many EPS bearers that need data forwarding in each PDU session in the EPS system, the mapping relationship between the QoS flow and the EPS bearer, the EPS bearer identifier and / or the QoS information of the EPS bearer. The message contains the channel information for data forwarding received from the MME. AMF sends direct forwarding indication information to SMF. The direct forwarding indication can indicate direct data forwarding or indirect data forwarding. AMF informs SMF whether to forward data directly or indirectly.

[0108] For indirect data forwarding, step 512 is executed. For direct data forwarding, step 512 may not be executed. SMF decides whether to execute step 512 based on the information received in step 503 or based on whether direct data forwarding or indirect data forwarding is received from AMF in this step. According to the method in which SMF decides based on the information received in step 503, if SMF receives that the direct data forwarding path is available, SMF can decide to use direct data forwarding. If SMF does not receive that the direct data forwarding path is available, SMF determines whether indirect data forwarding is available. Thus, SMF knows whether direct data forwarding or indirect data forwarding is used.

[0109] Step 512: SMF sends an N4 session modification message to UPF. The message contains PDU session information. The PDU session information contains the PDU session identifier, the information of the QoS flow contained in the PDU session, the number of EPS bearers that need data forwarding in each PDU session in the EPS system, the mapping relationship between the QoS flow and the EPS bearer, the EPS bearer identifier and / or the QoS information of the EPS bearer. The message contains the channel information for data forwarding received from the AMF.

[0110] The N4 session modification message includes the EPS bearer information included in the PDU session. The EPS bearer information includes the EPS bearer identifier and the channel information used by the EPS bearer for data forwarding. SMF informs UPF of the correspondence between the Qos flow and the EPS bearer in the PDU session. UPF knows the Qos flow information of the PDU session in the 5G system. UPF receives the EPS bearer information contained in the PDU session and the mapping relationship between the Qos flow and the EPS bearer from SMF.

[0111] SMF sends direct forwarding indication information to UPF. Direct forwarding indication can indicate direct data forwarding or indirect data forwarding. SMF informs UPF of direct data forwarding or indirect data forwarding.

[0112] For indirect data forwarding, SMF allocates channel information for data forwarding between NG-RAN and UPF, or UPF allocates channel information for data forwarding between NG-RAN and UPF and sends it to SMF. For indirect data forwarding, PDU session channel is used between NG-RAN and UPF for data forwarding. UPF allocates data forwarding channel information for the PDU session corresponding to the EPS bearer that receives data forwarding. The channel information includes the transport layer address and TEID. UPF sends the allocated channel information for data forwarding to SMF. SMF receives the N4 session modification response message from UPF. The message includes the channel information allocated by UPF for data forwarding between NG-RAN and UPF. For direct data forwarding, UPF does not need to allocate data forwarding channel information. Based on the information received in step 503 or this step, UPF knows whether it is direct data forwarding or indirect data forwarding. For direct data forwarding, step 512 may also not be executed.

[0113] Step 513, SMF sends an update SM context response message to AMF. For direct data forwarding, the message includes the channel information for data forwarding received by SMF from AMF. The channel information is used for direct data forwarding, and the channel information is for each EPS bearer. For indirect data forwarding, the message includes the channel information for data forwarding between NG-RAN and UPF allocated by SMF or UPF. The channel information can be for each PDU session.

[0114] Step 514, AMF sends a switching command message to NG-RAN. The message includes the channel information for data forwarding allocated by the destination to source transparent transmitter, E-UTRAN or UPF or SMF. The channel information for data forwarding corresponds to each PDU session or each E-RAB. For direct data forwarding, the channel information for data forwarding is for each E-RAB that accepts data forwarding. For indirect data forwarding, the channel information for data forwarding is for the PDU session to which each QoS flow that accepts data forwarding belongs. The message also includes the established PDU session information and the PDU session information that was not successfully established. The established PDU session information includes the established QoS flow information and the QoS flow information that was not successfully established.

[0115] Step 515: NG-RAN sends a handover command message to the UE.

[0116] NG-RAN forwards data.

[0117] If NG-RAN receives the data forwarding channel information corresponding to each PDU session, NG-RAN forwards the data to UPF. NG-RAN forwards the data to UPF on the channel corresponding to the PDU session for the Qos flow that requires data forwarding. NG-RAN sends the data of each Qos flow to UPF on the user plane channel allocated for the PDU session. For downlink data, NG-RAN sends the downlink data packet to UPF on the channel allocated for downlink data forwarding. UPF forwards the data to SGW. UPF adds the QFI corresponding to the Qos flow to the data packet header and forwards the data received from NG-RAN to SGW through the user plane channel allocated for the corresponding EPS bearer. UPF forwards the data of different Qos flows in the PDU session to SGW through the user plane channel allocated for the corresponding EPS bearer based on the mapping relationship between Qos flow and EPS bearer. Based on the mapping relationship between Qos flow and EPS bearer and the EPS bearer information that accepts data forwarding, UPF knows the Qos flow that accepts data forwarding, and UPF forwards the data of the Qos flow that accepts data forwarding to the user plane channel allocated for the corresponding EPS bearer and forwards it to SGW. For the QoS flow that does not accept data forwarding, there is no corresponding data forwarding channel, and the UPF discards the data.

[0118] If NG-RAN receives the channel information corresponding to each E-RAB, NG-RAN forwards the Qos flow data to the corresponding E-RAB channel. NG-RAN forwards the PDCP protocol data unit (SDU) to the corresponding E-RAB channel. The PDCP SDU does not carry a sequence number (SN). For direct data forwarding, the data is sent directly to the destination base station.

[0119] For indirect data forwarding, SGW forwards data to E-UTRAN. SGW sends the data received from UPF corresponding to each EPS bearer channel to E-UTRAN through the corresponding channel allocated by E-UTRAN. SGW forwards data to E-UTRAN according to the session transmission mode in EPS.

[0120] E-UTRAN receives the forwarded data from the E-RAB channel. E-UTRAN first sends the forwarded data to the UE, and then sends the data received from the new S1-U to the UE.

[0121] During the PDU session establishment or GBR QoS flow establishment process, the UE receives the EPS QoS information and / or EPS bearer identification information mapped by the QoS flow from the network. The UE associates the ongoing QoS flow with the EPS bearer identification contained in the handover command message. For QoS flows that do not have a corresponding EPS bearer, the UE can delete them.

[0122] Step 516: The UE sends a handover complete message to the E-UTRAN.

[0123] Step 517: E-UTRAN sends a handover notification message to MME, wherein the message includes information about the channel allocated by E-UTRAN for downlink data transmission.

[0124] Step 518: MME sends a modify bearer request message to SGW, wherein the message includes channel information of the S1 interface used for downlink data transmission.

[0125] Step 519, SGW sends a modify bearer request message to SMF. SMF may also have a PGW control plane function. SGW allocates channel information for downlink data transmission between SGW and UPF, and the channel information corresponds to each EPS bearer or each PDU session.

[0126] Step 520, SMF requests UPF to modify the session. SMF may also have the function of PGW control plane. SMF sends the channel information for downlink data transmission between SGW and UPF allocated by SGW to UPF, and the channel information corresponds to each EPS bearer or each PDU session. UPF sends a session modification response to SMF. UPF allocates the channel information for uplink data transmission between SGW and UPF, and UPF sends the channel information for uplink data transmission to SMF.

[0127] Step 521, SMF sends a modify bearer response message to SGW. The message includes the channel information between SGW and UPF for uplink data transmission allocated by UPF.

[0128] Step 522: The SGW sends a modify bearer response message to the MME.

[0129] So far, the description of the second embodiment of the switching method of the present invention is completed. This method can completely solve the problem of coexistence of different data forwarding methods when the UE moves between the EPS and 5GS systems, avoid data loss, ensure business continuity, ensure interoperability between equipment from different manufacturers, and reduce the configuration of operators.

[0130] The present invention supports switching method 2 such as Figure 6As shown. In this method, the source base station informs the destination base station of the source base station identifier or the source cell identifier through the core network, and the destination base station determines whether direct data forwarding is available, so that the destination base station decides how to allocate data forwarding channel information. This method solves the above two problems, so that data forwarding during the switching process is successfully executed, and the various entities in the network coordinate their work to ensure successful data forwarding. Detailed descriptions of steps not related to the present invention are omitted here. The method includes the steps of: Step 600: E-UTRAN decides to hand over the UE to NG-RAN The E-UTRAN here can be an eNB connected to the EPC. The NG-RAN can be a gNB or an eNB connected to the 5GC or a centralized unit CU in the gNB. The eNB connected to the 5GC can also be called an ng-eNB.

[0131] The user plane path before switching is PGW-U+UPF (UPF has PGW user plane function, hereinafter referred to as UPF), SGW to E-UTRAN. SGW needs to support the interface with PGW-U+UPF. UE has one or more PDU sessions in progress. Each PDU session contains one or more EPS bearers. During the PDU session establishment or EPS bearer establishment process, the EPS bearer is allocated QoS information and / or QoS flow identifier of the mapped QoS flow. The default EPS bearer is mapped to the non-guaranteed service rate (non-GBR) QoS flow. The QoS information and / or QoS flow identifier of the QoS flow mapped by the EPS bearer can be allocated by the PCC or PGW control plane function. In order to support switching between different systems, the PGW control plane function can also have SMF function. In the scenario of PCC deployment, the policy control and charging function (PCRF) provides the QoS and / or QoS flow identifier of the QoS flow mapped by the EPS bearer to the SMF. In order to support switching between different systems, there is also a policy control function (PCF) on the PCRF. SMF sends the QoS and / or QoS flow identifier of the QoS flow mapped by the EPS bearer to the UE through the MME, for example, through the non-access layer message PDN connection establishment message to the UE. During the PDU session establishment or EPS bearer establishment process, SMF can also send the QoS and / or QoS flow identifier of the QoS flow mapped by the EPS bearer to the E-UTRAN through the MME. E-UTRAN can send the mapping information to the UE through an RRC message. The E-RAB and EPS bearer identifiers are the same or have a one-to-one correspondence. In the core network, it is an EPS bearer, and in the access network, it is called an E-RAB. The E-RAB identifier and the EPS bearer identifier are the same or have a one-to-one correspondence. In the core network, it is an EPS bearer identifier, and in the access network, it is called an E-RAB identifier.

[0132] Step 601, E-UTRAN sends a handover request message to MME. The message includes the identifier of the target NG-RAN node and the transparent transmitter from the source to the target. The message also includes the identifier information indicating the AMF to which the target NG-RAN node is connected. The identifier information may be a tracking area identifier, a network slice identifier, an AMF pool identifier, or an AMF identifier, etc.

[0133] The message contains information that a direct data forwarding path is available.

[0134] The message includes the identifier of the source base station or the identifier of the source cell. The information may be included in a transparent transmitter from the source to the destination or directly included in a handover requirement message.

[0135] The source-to-destination transparent transmitter includes a PDU session identifier, an identifier of the Qos flow in the PDU session, and downlink data forwarding proposed for the Qos flow. The eNB obtains the PDU session identifier corresponding to the EPS bearer and / or the Qos flow identifier in the PDU session through the PDN connection establishment process or through the switching process. The Qos information of the mapped Qos flow may also be obtained. The eNB decides whether to propose data forwarding based on the mapping of the Qos flow from the E-RAB to the PDU session or from the E-RAB to the PDU session and the Qos information. The eNB may consider other factors such as whether there is buffered data to make a decision without affecting the main content of the present invention.

[0136] Step 602, MME sends a forward relocation request message to AMF. MME selects and finds AMF according to the identification information of the AMF to which the destination NG-RAN node is connected contained in the handover requirement message. The message includes the identification of the destination NG-RAN node, the source-to-destination transparent transmitter and UE context information. The UE context information includes UE mobility management MM context information and session management context. The message includes the type of handover. The message includes the identification of the source base station or the identification of the source cell. The information can be included in the source-to-destination transparent transmitter or directly included in the forward relocation request message.

[0137] The MME sends a direct forwarding indication to the AMF. If the MME receives a message from the source E-UTRAN that direct data forwarding is not feasible, the MME decides whether indirect data forwarding is feasible. The MME informs the AMF of whether direct data forwarding is or is not. The MME can also inform the AMF of the information that data forwarding is not feasible. The data forwarding not feasible means that both direct data forwarding and indirect data forwarding are not feasible. Alternatively, the MME can also inform the AMF of the information that direct data forwarding is available.

[0138] The MME determines whether indirect data forwarding is feasible. The MME informs the AMF of whether indirect data forwarding is feasible. The data forwarding is not feasible means that indirect data forwarding is not feasible.

[0139] Step 603a, AMF sends a Create Session (SM) Context Request message to SMF. AMF converts the received EPS UE context into a 5GS UE context. AMF can also exchange with PCRF to obtain the converted 5GS UE context. AMF selects the SMF that serves the UE.

[0140] According to the information received in the forwarding relocation request message, the AMF knows that the handover is between different systems, and the AMF requests the SMF to provide the SM context. The AMF sends the message to each SMF serving the UE.

[0141] AMF sends a direct forwarding indication or direct data forwarding is available to SMF, and AMF informs SMF of the information that direct data forwarding or indirect data forwarding is available.

[0142] Step 604: SMF initiates the N4 session modification process with UPF. SMF sends a direct forwarding indication to UPF, and SMF informs UPF of the available direct data forwarding or indirect data forwarding. SMF can also inform UPF of the available direct data forwarding.

[0143] Step 603b, SMF sends a create session context response message to AMF. The message contains the SM context of the UE. The SM context also contains the mapping relationship between the EPS bearer and the QoS flow in the PDU session. If the SMF has a mapped EPS bearer context when the AMF requests the SM context, the SMF always feeds back the mapped EPS bearer context to the AMF at the same time. Or the SMF sends the mapped EPS bearer context to the AMF only when the AMF requests the mapped EPS context at the same time.

[0144] The 5GS UE context contains the QoS information in the 5G system. The QoS information in the 5G system contains QoS rules and / or QoS profiles. AMF can map EPS QoS information into 5G QoS information, or AMF interacts with the 5G Policy Control Function (5G-PCF) to derive 5G QoS information.

[0145] The SMF determines that direct data forwarding, indirect data forwarding or data forwarding is not feasible. If the direct forwarding received by the SMF indicates that direct data forwarding is feasible, the SMF may decide to use direct data forwarding. If the direct forwarding received by the SMF indicates indirect data forwarding and indirect data forwarding is feasible, the SMF decides to use indirect data forwarding. If the direct forwarding received by the SMF indicates indirect data forwarding but there is no indirect data forwarding connection, the SMF determines that data forwarding is not possible. The SMF includes the information that direct data forwarding, indirect data forwarding or data forwarding is not feasible in the N2 session management (SM) information container. Or, SMF determines that indirect data forwarding or data forwarding is not feasible. SMF informs the target NG-RAN of the information. Or, The SMF determines whether indirect data forwarding is not feasible. The SMF informs the destination NG-RAN of the information that indirect data forwarding is not feasible and whether direct data forwarding is available.

[0146] In step 605, AMF sends a handover request message to NG-RAN. The message contains information about the PDU session to be established. The information about the PDU session contains session identifier, session QoS information, QoS flow information, uplink channel information for each session, and / or a source-to-destination transparent transmitter. The message contains the type of handover. The message contains an identifier of the source base station or an identifier of the source cell. The identifier of the source base station can be sent to the destination base station through a source-to-destination transparent transmitter, or can be sent to the destination base station through the handover requirement of step 601, the forwarding relocation request of step 602, and the handover request message of this step.

[0147] The message includes information that data forwarding is impossible. The impossible data forwarding means that indirect data forwarding is impossible, or both direct data forwarding and indirect data forwarding are not feasible. The message may also include information that direct data forwarding is available. The above information may be included in the N2 SM information container.

[0148] The message may also include a mapping relationship between the Qos flow in the PDU session and the EPS bearer, that is, an E-RAB identifier mapped by the Qos flow and / or mapped Qos information.

[0149] Step 606: NG-RAN sends a handover request confirmation message to AMF. The message includes one or more of the following information: The transparent transmitter from the destination to the source may also include a mapping relationship between the Qos flow in the PDU session and the EPS bearer, that is, the EPS bearer identifier mapped by the Qos flow and / or the mapped Qos information.

[0150] The NG-RAN accepts the PDU session information list established. The PDU session information list includes the PDU session identifier, the downlink channel information of the NG3 interface used for the PDU session, the Qos flow information accepted by the PDU session, and the Qos flow information not accepted.

[0151] If the NG-RAN does not receive the data forwarding impossible, the destination NG-RAN determines whether direct data forwarding is feasible based on the received source base station identifier or source cell identifier, and thus decides whether direct data forwarding or indirect data forwarding is feasible. If direct data forwarding is feasible, direct data forwarding is used; if direct data forwarding is not feasible, indirect data forwarding is used. If the NG-RAN receives the data forwarding impossible, the NG-RAN does not allocate the data forwarding channel identifier.

[0152] Another method for NG-RAN to decide whether to forward data directly or indirectly is: the data forwarding impossible received from AMF means that indirect data forwarding is impossible. According to the received source base station identifier or source cell identifier, the destination NG-RAN determines whether direct data forwarding is feasible. If direct data forwarding is feasible, direct data forwarding is used. If direct data forwarding is not feasible and indirect data forwarding is not received, indirect data forwarding is used. If direct data forwarding is not feasible and indirect data forwarding is not feasible is received, NG-RAN does not allocate a data forwarding channel identifier.

[0153] Another method for NG-RAN to decide whether to forward data directly or indirectly is: the data forwarding impossible received from AMF means that indirect data forwarding is impossible. Based on the received direct data forwarding available information, the destination NG-RAN decides whether to forward data directly or indirectly. If direct data forwarding is available, direct data forwarding is used. If direct data forwarding is not feasible and indirect data forwarding is not received, indirect data forwarding is used. If direct data forwarding is not feasible and indirect data forwarding is not feasible is received, NG-RAN does not allocate a data forwarding channel identifier.

[0154] Another method for NG-RAN to determine direct data forwarding or indirect data forwarding is: if NG-RAN does not receive data forwarding not possible, based on the received information that direct data forwarding is available, the destination NG-RAN determines direct data forwarding or indirect data forwarding, uses direct data forwarding if direct data forwarding is available, and uses indirect data forwarding if direct data forwarding is not feasible. If data forwarding is not feasible, NG-RAN does not allocate a data forwarding channel identifier.

[0155] If it is direct data forwarding, for the QoS flow that NG-RAN accepts data forwarding or the E-RAB that accepts data forwarding, NG-RAN allocates downlink data forwarding channel information to the corresponding E-RAB, and includes the E-RAB identifier and the downlink channel information corresponding to the E-RAB allocated by NG-RAN in the handover request confirmation message. If it is indirect data forwarding, for the QoS flow that NG-RAN accepts data forwarding, NG-RAN allocates downlink data forwarding channel information to the PDU session to which it belongs, and includes the PDU session identifier and the downlink channel information corresponding to the PDU session allocated by NG-RAN in the handover request confirmation message, and may also include a list of QoS flows that accept data forwarding. If data forwarding is not feasible, NG-RAN does not need to allocate data forwarding channel information.

[0156] The NG-RAN does not accept the established PDU session information list. The PDU session information list includes the PDU session identifier and the reason for not accepting.

[0157] The message contains information about direct data forwarding or indirect data forwarding. The information can be explicit or implicit. The so-called implicit method means that if the data forwarding channel information contained in the message corresponds to each E-RAB, it is direct data forwarding, and if the data forwarding channel information contained in the message corresponds to each PDU session, it is indirect data forwarding. In step 607, AMF sends an update SM context request message to SMF. If the channel information for data forwarding is received from NG-RAN, AMF sends the data forwarding channel information received from NG-RAN to SMF. AMF sends the channel information for data forwarding received from NG-RAN to SMF. AMF sends information on direct data forwarding or indirect data forwarding to SMF. AMF can inform SMF in an explicit manner whether direct data forwarding, indirect data forwarding or data forwarding is not feasible. AMF can also inform SMF in an implicit manner, that is, if SMF receives the data forwarding channel information corresponding to each E-RAB, it is direct data forwarding, if it receives the data forwarding channel information corresponding to each PDU session, it is indirect data forwarding, and if there is no data forwarding channel information, data forwarding is not feasible or data forwarding is not accepted by the destination base station. The message includes the PDU session to which the EPS bearer belongs. The message may also include a mapping relationship between the EPS bearer and the Qos flow in the PDU session.

[0158] Step 608, SMF initiates the session modification process between SMF and UPF. If SMF receives the data forwarding channel information of each PDU session, SMF sends the NG3 interface downlink data forwarding channel information allocated by NG-RAN to UPF through the N4 session modification process, and the data forwarding channel information is for each PDU session. SMF allocates data forwarding channel information between SGW and UPF, or UPF allocates channel information for data forwarding between SGW and UPF and sends it to SMF, and the data forwarding channel information is for each E-RAB. The N4 session modification message includes the PDU session to which the EPS bearer belongs. The N4 session establishment or N4 session modification message may also include the mapping relationship between the EPS bearer and the Qos flow in the PDU session. If SMF receives the data forwarding channel information of each E-RAB, it is direct data forwarding, and SMF or UPF does not need to allocate data forwarding channel information.

[0159] Step 609, SMF sends an update SM context response message to AMF. SMF sends the channel information used for data forwarding to AMF. For direct data forwarding, SMF sends the channel information corresponding to each E-RAB received from AMF to AMF, and the channel information corresponding to each E-RAB is allocated by the target NG-RAN. For indirect data forwarding, SMF sends the channel information of each E-RAB allocated by SMF or UPF to AMF, and the channel information is used for data forwarding between SGW and UPF.

[0160] The update SM context response message includes information on direct data forwarding or indirect data forwarding.

[0161] Step 610, AMF sends a forwarding relocation response message to MME. The message contains data forwarding channel information. For direct data forwarding, the channel information is allocated by the destination NG-RAN. For indirect data forwarding, the channel information is the channel information received from SMF for data forwarding between SGW and UPF. The message contains a transparent transmitter from the destination to the source. The forwarding relocation response message contains information on direct data forwarding or indirect data forwarding.

[0162] Step 611, if the MME receives the channel information for data forwarding, for indirect data forwarding, the MME sends a request message for creating an indirect data forwarding channel to the SGW. The message is used to send the channel information for data forwarding between the SGW and the UPF to the SGW. The SGW sends a response message for creating an indirect data forwarding channel to the MME. The message contains the uplink channel information allocated by the SGW for S1 interface data forwarding. For direct data forwarding, this step does not need to be performed. The MME knows whether it is direct data forwarding or indirect data forwarding based on the information on the availability of the direct data forwarding path received from the source base station or the information on direct data forwarding or indirect data forwarding received from the AMF.

[0163] Step 612: MME sends a handover command message to E-UTRAN, wherein the message includes a transparent transmitter from the destination to the source, and the handover type.

[0164] The message includes data forwarding channel information. For indirect data forwarding, the channel information is allocated by the SGW. For direct data forwarding, the channel information is allocated by the destination NG-RAN.

[0165] Step 613: E-UTRAN sends a handover command message to the UE.

[0166] The message may also include a mapping relationship between the Qos flow and the EPS bearer in the PDU session, that is, the EPS bearer identifier mapped by the Qos flow and / or the mapped Qos information.

[0167] E-UTRAN forwards data. For E-RAB that receives the data forwarding channel information, it means that the destination base station has accepted the data forwarding, and E-UTRAN forwards the data to the corresponding channel. For direct data forwarding, the destination NG-RAN directly receives the data forwarded by E-UTRAN. For indirect data forwarding, SGW receives the data forwarded by E-UTRAN. SGW forwards the data to UPF. SGW forwards the data to UPF on the corresponding channel for each EPS bearer that requires data forwarding. UPF forwards the data to NG-RAN. UPF sends the data belonging to the same PDU session received from the SGW corresponding to the channel of each EPS bearer to NG-RAN through the PDU session channel, that is, UPF maps multiple channels to one channel. UPF forwards data to NG-RAN according to the session transmission method in 5GS. For example, each PDU session sends downlink data through several Qos flows, and how to set the Qos flow header. UPF adds the Qos flow identifier (QFI) to the header of the data packet forwarded to the destination NG-RAN.

[0168] NG-RAN receives the forwarded data from the PDU session channel, and NG-RAN sends the received data to the UE in the existing manner. NG-RAN receives the forwarded data from the E-RAB channel, and NG-RAN does not need to process the SDAP layer, and directly sends the data to the PDCP layer of the corresponding DRB. Based on the mapping relationship between the E-RAB ID(s) and the Qos Flow ID(s) received in the handover request message, NG-RAN knows the DRB corresponding to the E-RAB, and thus directly sends the received forwarded data to the PDCP entity of the corresponding DRB. NG-RAN first sends the forwarded data to the UE, and then sends the data received from the new NG-U to the UE.

[0169] During the PDU session establishment or EPS bearer establishment process, the UE receives the QoS information and / or QoS flow information of the QoS flow mapped by the EPS bearer from the network. The UE associates the correspondence between the ongoing EPS bearer and the QoS flow contained in the handover command message. For EPS bearers that do not have a corresponding QoS flow, the UE can delete them.

[0170] Or the UE obtains the mapping relationship between the QoS flow in the PDU session and the EPS bearer from the handover command message. The UE associates the ongoing EPS bearer with the corresponding relationship between the QoS flow contained in the handover command message. For the EPS bearer without corresponding QoS flow, the UE can delete it.

[0171] Step 614: The UE sends a handover complete message to the NG-RAN.

[0172] Step 615: NG-RAN sends a handover notification message to AMF, wherein the message includes information about the channel allocated by NG-RAN for downlink data transmission.

[0173] Step 616, AMF sends an update SM context request message to SMF.

[0174] Step 617: SMF sends an N4 session modification message to UPF. UPF sends an N4 session modification response message to SMF.

[0175] AMF sends the channel information of downlink data transmission allocated by NG-RAN to UPF through AMF.

[0176] Step 618, SMF sends an update SMF context response message to AMF.

[0177] So far, the description of the second switching method of the present invention is completed. This method can completely solve the problem of coexistence of different data forwarding methods when the UE moves between the LTE and 5G systems, avoid data loss, ensure business continuity, ensure interoperability between equipment from different manufacturers, and reduce the configuration of operators.

[0178] The present invention supports three switching methods such as Figure 7 As shown. The method is applicable to the second mode where two data forwarding methods coexist, that is, which data forwarding method is specifically supported depends on the implementation of the NG-RAN node and the UPF. The method is used for switching from 5GS to EPS. Detailed descriptions of steps not related to the present invention are omitted here. The method comprises the steps of: Step 701, NG-RAN decides to hand over the UE to E-UTRAN.

[0179] Here, E-UTRAN can be an eNB connected to EPC. NG-RAN can be a gNB or an eNB connected to 5GC or a centralized unit CU in a gNB.

[0180] The user plane path before handover is from UPF to NG-RAN. SGW needs to support the interface with UPF. UPF can include the functions of PGW user plane and perform the functions of user plane anchor point during handover between different RATs.

[0181] The UE has one or more PDU sessions in progress. Each PDU session contains one or more QoS flows. During the PDU session establishment or guaranteed service rate (GBR) QoS flow establishment process, the mapped EPS QoS information and / or EPS bearer identifier are allocated to the QoS flow. The non-guaranteed service rate (non-GBR) QoS flow is mapped to the default EPS bearer. The GBR QoS flow is mapped to the EPS dedicated bearer. The EPS QoS information mapped by the QoS flow can be allocated by the PCC or SMF. The EPS bearer identifier mapped by the QoS flow can be allocated by the SMF or AMF. In order to support switching between different systems, the SMF can also have the function of the PGW control plane. In the scenario of PCC deployment, the policy control function (PCF) provides the EPS QoS mapped by the QoS flow to the SMF. In order to support switching between different systems, the PCF can also have a policy control and charging function (PCRF). The SMF sends the EPS QoS information and / or EPS bearer identifier mapped by the QoS flow to the UE through the AMF, for example, through the non-access layer message PDU session establishment message to the UE. During the PDU session establishment or guaranteed service rate (GBR) QoS flow establishment process, SMF can also send EPS QoS information and / or E-RAB identifier mapped by QoS flow to NG-RAN through AMF. AMF sends EPS QoS information and / or E-RAB identifier mapped by QoS flow to NG-RAN through initial context establishment request message or PDU session resource establishment request message. NG-RAN can send EPS QoS information and / or E-RAB identifier mapped by QoS flow to UE through RRC message. E-RAB and EPS bearer identifiers are the same or have one-to-one correspondence. In the core network, it is EPS bearer, and in the access network, it is called E-RAB. The E-RAB identifier and EPS bearer identifier are the same or have one-to-one correspondence. In the core network, it is EPS bearer identifier, and in the access network, it is called E-RAB identifier.

[0182] In step 702, NG-RAN sends a switching request message to AMF. The message includes the identifier of the target eNB and the transparent transmitter from the source to the target. The transparent transmitter from the source to the target includes the E-RAB identifier and the downlink data forwarding proposed for this E-RAB. NG-RAN obtains the EPS bearer identifier mapped by the Qos flow in the PDU session through the PDU session establishment process or through the switching process. The mapped EPS Qos information may also be obtained. NG-RAN decides whether to propose data forwarding based on the mapping of the Qos flow to the E-RAB and the Qos information. NG-RAN can consider other factors such as whether there is buffer data to make the decision without affecting the main content of the present invention. The message also includes that the source NG-RAN node supports data forwarding of the PDU session channel and / or data forwarding of the E-RAB channel. The message includes information that a direct data forwarding path is available. Direct data forwarding can also implicitly inform the AMF that the source NG-RAN supports data forwarding of the E-RAB channel.

[0183] Here, the AMF obtains the data forwarding method supported by the NG-RAN node through a UE-specific message. Another way for the AMF to obtain that the NG-RAN node supports data forwarding of the PDU session channel and / or data forwarding of the E-RAB channel is through a public process (a non-UE-specific process), that is, the AMF obtains the data forwarding method supported by the NG-RAN through the NG establishment process. Corresponding to this method, the NG-RAN includes information that the NG-RAN node supports data forwarding of the PDU session channel and / or data forwarding of the E-RAB channel in the NG establishment request message sent to the AMF. The AMF saves the received information and uses it when the UE needs to be switched out of the NG-RAN node later. The AMF sends an NG establishment response message to the NG-RAN node.

[0184] The message also includes identification information indicating the MME to which the target eNB is connected. The identification information may be a tracking area identification or an MME identification.

[0185] The message also contains the type of handover.

[0186] In step 703a, AMF sends a session management SM context request message to SMF. Based on the information received in the switching requirement message, AMF knows that the switching is between different systems, and AMF requests SMF to provide SM context. AMF can also request EPS bearer context. AMF sends the message to each SMF serving the UE. The message also includes information that the source NG-RAN node supports data forwarding of the PDU session channel and / or data forwarding of the E-RAB channel. The message includes information that a direct data forwarding path is available. Direct data forwarding can also implicitly inform the SMF that the source NG-RAN supports data forwarding of the E-RAB channel.

[0187] Step 703b, SMF sends an N4 session modification request message to UPF. The message includes information that the source NG-RAN node supports data forwarding of PDU session channels and / or data forwarding of E-RAB channels. The message includes information that a direct data forwarding path is available. Direct data forwarding can also implicitly inform UPF that the source NG-RAN supports data forwarding of E-RAB channels. UPF sends an N4 session modification response message to SMF.

[0188] Step 703c, SMF sends an SM context response message to AMF. The message contains the SM context of the UE. The SM context also contains the mapped EPS bearer context, such as the EPS bearer identifier and / or EPS QoS information. If there is a mapped EPS bearer context when AMF requests the SM context, SMF always feeds back the mapped EPS bearer context to AMF at the same time. Or when AMF requests the SM context from SMF, it also indicates the requested mapped EPS bearer context. SMF sends the mapped EPS bearer context to AMF only when AMF requests the mapped EPS context at the same time.

[0189] Step 704, AMF sends a forward relocation request message to MME. AMF selects and finds MME according to the identification information of the MME to which the target eNB is connected contained in the handover requirement message. The identification information of the MME to which the target eNB is connected may be TAI. The message includes the identification of the target eNB, the source-to-target transparent transmitter and the mapped EPS UE context information. The mapped EPS UE context information includes UE mobility management MM context information and session SM context information.

[0190] If the AMF does not receive information from the source NG-RAN that direct data forwarding is available, the AMF determines whether indirect data forwarding is possible. If direct data forwarding is possible, direct data forwarding is used. Or if direct data forwarding is possible and the source base station supports E-RAB channel data forwarding, direct data forwarding is used. The AMF informs the MME whether direct data forwarding or indirect data forwarding is available or whether data forwarding is not available.

[0191] Step 705: MME sends a create session request message to SGW, wherein the message includes EPS bearer context information.

[0192] Step 706: SGW sends a create session response message to MME, wherein the message includes channel information of the S1 interface allocated by SGW for uplink data transmission.

[0193] Step 707, MME sends a handover request message to E-UTRAN. The message includes a transparent transmitter from source to destination and an E-EAB context. The E-RAB context includes the uplink channel information of the E-RAB to be established and the S1 interface allocated by the SGW. The E-RAB context includes information on whether data forwarding is feasible. The message includes a handover type, and the specific content is the same as in step 702, which will not be repeated here.

[0194] Step 708: E-UTRAN sends a handover request confirmation message to MME. The message includes a list of established E-RABs and a list of failed established E-RABs, and a transparent transmitter from the destination to the source. For the established RAB, it also includes the channel information for sending downlink data on the S1 interface. For the established E-RAB, if the source eNB proposes downlink data forwarding, data forwarding is feasible, and the target eNB accepts downlink data forwarding, the target eNB includes the channel information for S1 interface data forwarding allocated by E-UTRAN for each E-RAB that needs downlink data forwarding.

[0195] Step 709, MME requests SGW to create an indirect data forwarding channel. This step is performed only when indirect data forwarding needs to be performed. If MME receives S1 interface downlink channel information for data forwarding from E-UTRAN, MME requests SGW to create an indirect data forwarding channel. MME sends the transport layer address and TEID for data forwarding assigned by eNB to SGW. The transport layer address and TEID correspond to each E-RAB.

[0196] SGW sends an indirect data forwarding channel creation response message to MME. The message includes information allocated by SGW for data forwarding between SGW and UPF. The information used for data forwarding between SGW and UPF includes E-RAB identification and channel information used by the E-RAB for data forwarding. The channel information includes the transport layer address and TEID allocated by SGW. SGW allocates downlink data forwarding channel information to the E-RAB that needs downlink data forwarding. SGW allocates uplink data forwarding channel information to the E-RAB that needs uplink data forwarding. The data forwarding channel information included in the E-RAB information may include uplink and / or downlink data forwarding channel information.

[0197] When indirect data forwarding is feasible, step 709 is performed.

[0198] Step 710, the MME sends a forwarding relocation response message to the AMF. The message includes channel information for data forwarding. For direct data forwarding, the data forwarding channel information is received by the MME from the destination base station. For indirect data forwarding, the channel information is the SGW allocation received by the MME from the SGW. The channel information is for each EPS bearer. The data forwarding channel information may include downlink and / or uplink data forwarding channel information. The message includes a transparent transmitter from the destination to the source.

[0199] MME directly sends the E-RAB information to AMF, which then converts it.

[0200] Step 711, AMF sends an update SM context request message to SMF. The message contains information about direct data forwarding or indirect data forwarding. AMF requests SMF to create a data forwarding channel. For indirect data forwarding, AMF requests SMF to create a data forwarding channel. The message contains PDU session information. The PDU session information contains the PDU session identifier, the QoS flow information contained in the PDU session, how many EPS bearers in the EPS system that need data forwarding for each PDU session, the mapping relationship between the QoS flow and the EPS bearer, the EPS bearer identifier and / or the QoS information of the EPS bearer. The message contains information for data forwarding received from the MME. The message also contains information that the source NG-RAN node supports data forwarding of the PDU session channel and / or data forwarding of the E-RAB channel.

[0201] Step 712, SMF sends an N4 session modification message to UPF. The message contains PDU session information. The PDU session information contains the PDU session identifier, the information of the QoS flow contained in the PDU session, the number of EPS bearers that need data forwarding in each PDU session in the EPS system, the mapping relationship between the QoS flow and the EPS bearer, the EPS bearer identifier and / or the QoS information of the EPS bearer. The message contains the information for data forwarding received from the AMF. The message contains information on direct data forwarding or indirect data forwarding.

[0202] The N4 session modification message includes the EPS bearer information included in the PDU session. The EPS bearer information includes the EPS bearer identifier and the channel information used by the EPS bearer for data forwarding. SMF informs UPF of the correspondence between the Qos flow and the EPS bearer in the PDU session. UPF knows the Qos flow information of the PDU session in the 5G system. UPF receives the EPS bearer information contained in the PDU session and the mapping relationship between the Qos flow and the EPS bearer from SMF.

[0203] The message also includes that the source NG-RAN node supports data forwarding of the PDU session channel and / or data forwarding of the E-RAB channel.

[0204] For indirect data forwarding, SMF allocates channel information for data forwarding between NG-RAN and UPF, or UPF allocates channel information for data forwarding between NG-RAN or UPF and sends it to SMF. If the source NG-RAN supports data forwarding of PDU session channels, UPF allocates data forwarding channel information for the PDU session corresponding to the EPS bearer receiving data forwarding. If the source NG-RAN supports data forwarding of E-RAB channels, UPF allocates data forwarding channel information for the EPS bearer receiving data forwarding. If the source NG-RAN node supports data forwarding of PDU session channels and data forwarding of E-RAB channels, UPF decides to allocate data forwarding channel information for each PDU session or each E-RAB. The channel information includes the transport layer address and TEID.

[0205] UPF sends the allocated channel information for data forwarding to SMF. SMF receives the N4 session modification response message from UPF. The message contains the channel information allocated by UPF for data forwarding between NG-RAN and UPF. For direct data forwarding, UPF does not need to allocate data forwarding channel information. Based on the information received in step 703 or this step, UPF knows whether it is direct data forwarding or indirect data forwarding. For direct data forwarding, step 712 may not be performed.

[0206] Step 713, SMF sends an update SM context response message to AMF. For direct data forwarding, the message includes the channel information for data forwarding received by SMF from AMF. The channel information is used for direct data forwarding, and the channel information is for each EPS bearer. For indirect data forwarding, the message includes the channel information for data forwarding between NG-RAN and UPF allocated by UPF or SMF. The channel information can be for each PDU session or each E-RAB.

[0207] Step 714, AMF sends a switching command message to NG-RAN. The message includes the channel information for data forwarding allocated by the destination to source transparent transmitter, E-UTRAN or UPF or SMF. The channel information for data forwarding corresponds to each PDU session or each E-RAB. For direct data forwarding, the channel information for data forwarding is for each E-RAB that accepts data forwarding. For indirect data forwarding, the channel information for data forwarding is for the PDU session to which each QoS flow that accepts data forwarding belongs. The message also includes the established PDU session information and the PDU session information that was not successfully established. The established PDU session information includes the established QoS flow information and the QoS flow information that was not successfully established.

[0208] Step 715: NG-RAN sends a handover command message to the UE.

[0209] NG-RAN forwards data.

[0210] If NG-RAN receives the channel information corresponding to each PDU session, NG-RAN forwards the data to UPF. NG-RAN forwards the data to UPF on the channel corresponding to the PDU session for the Qos flow that requires data forwarding. NG-RAN sends the data of each Qosflow to UPF on the user plane channel allocated for the PDU session. For downlink data, NG-RAN sends the downlink data packet to UPF on the channel allocated for downlink data forwarding. UPF forwards the data to SGW. UPF adds the QFI corresponding to the Qos flow to the data packet header and forwards the data received from NG-RAN to SGW through the user plane channel allocated for the corresponding EPS bearer. UPF forwards the data of different Qos flows in the PDU session to SGW through the user plane channel allocated for the corresponding EPS bearer based on the mapping relationship between Qos flow and EPS bearer. Based on the mapping relationship between Qos flow and EPS bearer and the EPS bearer information that accepts data forwarding, UPF knows the Qos flow that accepts data forwarding, and UPF forwards the data of the Qos flow that accepts data forwarding to the user plane channel allocated for the corresponding EPS bearer and forwards it to SGW. For the QoS flow that does not accept data forwarding, there is no corresponding data forwarding channel, and the UPF discards the data.

[0211] If NG-RAN receives the channel information corresponding to each E-RAB, NG-RAN forwards the Qos flow data to the corresponding E-RAB channel. NG-RAN forwards the PDCP SDU to the corresponding E-RAB channel. The PDCP SDU does not carry a SN. For indirect data forwarding, the data is sent to the UPF, and the UPF forwards the data to the SGW. For direct data forwarding, the data is sent directly to the destination base station.

[0212] SGW forwards data to E-UTRAN. SGW sends the data received from UPF corresponding to each EPS bearer channel to E-UTRAN through the corresponding channel allocated by E-UTRAN. SGW forwards data to E-UTRAN according to the session transmission mode in EPS.

[0213] E-UTRAN receives the forwarded data from the E-RAB channel. E-UTRAN first sends the forwarded data to the UE, and then sends the data received from the new S1-U to the UE.

[0214] During the PDU session establishment or GBR QoS flow establishment process, the UE receives the EPS QoS information and / or EPS bearer identification information mapped by the QoS flow from the network. The UE associates the ongoing QoS flow with the EPS bearer identification contained in the handover command message. For QoS flows that do not have a corresponding EPS bearer, the UE can delete them.

[0215] Step 716: The UE sends a handover complete message to the E-UTRAN.

[0216] Step 717: E-UTRAN sends a handover notification message to MME, wherein the message includes information about the channel allocated by E-UTRAN for downlink data transmission.

[0217] Step 718: MME sends a modify bearer request message to SGW, wherein the message includes channel information of the S1 interface used for downlink data transmission.

[0218] Step 719, SGW sends a modify bearer request message to SMF. SMF may also have a PGW control plane function. SGW allocates channel information for downlink data transmission between SGW and UPF, and the channel information corresponds to each EPS bearer or each PDU session.

[0219] Step 720, SMF requests UPF to modify the session. SMF may also have the function of PGW control plane. SMF sends the channel information for downlink data transmission between SGW and UPF allocated by SGW to UPF, and the channel information corresponds to each EPS bearer or each PDU session. UPF sends a session modification response to SMF. UPF allocates the channel information for uplink data transmission between SGW and UPF, and UPF sends the channel information for uplink data transmission to SMF.

[0220] Step 721, SMF sends a modify bearer response message to SGW. The message includes the channel information between SGW and UPF for uplink data transmission allocated by UPF.

[0221] Step 722: SGW sends a modify bearer response message to MME.

[0222] So far, the description of switching method three of the present invention is completed. This method can completely solve the problem of data forwarding when the UE moves between the EPS and 5GS systems when the data forwarding methods supported by devices from different manufacturers in the network are different, avoid data loss, ensure business continuity, ensure interoperability between devices from different manufacturers, and reduce the configuration of operators.

[0223] The present invention supports switching method 4 such as Figure 8As shown. The method is applicable to the second mode where two data forwarding methods coexist, that is, which data forwarding method is specifically supported depends on the implementation of the NG-RAN node and the UPF. The method is used for switching from EPS to 5GS. Detailed descriptions of steps not related to the present invention are omitted here. The method comprises the steps of: Step 800: E-UTRAN decides to handover the UE to NG-RAN.

[0224] The E-UTRAN here can be an eNB connected to the EPC. The NG-RAN can be a gNB or an eNB connected to the 5GC or a centralized unit CU in the gNB. The eNB connected to the 5GC can also be called an ng-eNB.

[0225] The user plane path before switching is PGW-U+UPF (UPF has PGW user plane function, hereinafter referred to as UPF), SGW to E-UTRAN. SGW needs to support the interface with PGW-U+UPF. UE has one or more PDU sessions in progress. Each PDU session contains one or more EPS bearers. During the PDU session establishment or EPS bearer establishment process, the EPS bearer is allocated QoS information and / or QoS flow identifier of the mapped QoS flow. The default EPS bearer is mapped to the non-guaranteed service rate (non-GBR) QoS flow. The QoS information and / or QoS flow identifier of the QoS flow mapped by the EPS bearer can be allocated by the PCC or PGW control plane function. In order to support switching between different systems, the PGW control plane function can also have SMF function. In the scenario of PCC deployment, the policy control and charging function (PCRF) provides the QoS and / or QoS flow identifier of the QoS flow mapped by the EPS bearer to the SMF. In order to support switching between different systems, there is also a policy control function (PCF) on the PCRF. SMF sends the QoS and / or QoS flow identifier of the QoS flow mapped by the EPS bearer to the UE through the MME, for example, through the non-access layer message PDN connection establishment message to the UE. During the PDU session establishment or EPS bearer establishment process, SMF can also send the QoS and / or QoS flow identifier of the QoS flow mapped by the EPS bearer to the E-UTRAN through the MME. E-UTRAN can send the mapping information to the UE through an RRC message. The E-RAB and EPS bearer identifiers are the same or have a one-to-one correspondence. In the core network, it is an EPS bearer, and in the access network, it is called an E-RAB. The E-RAB identifier and the EPS bearer identifier are the same or have a one-to-one correspondence. In the core network, it is an EPS bearer identifier, and in the access network, it is called an E-RAB identifier.

[0226] Step 801, E-UTRAN sends a handover requirement message to MME. The message includes the identifier of the target NG-RAN node and the transparent transmitter from the source to the target. The message also includes the identifier information indicating the AMF to which the target NG-RAN node is connected. The identifier information may be a tracking area identifier, a network slice identifier, an AMF pool identifier, or an AMF identifier, etc.

[0227] The message contains information that a direct data forwarding path is available.

[0228] The source-to-destination transparent transmitter includes a PDU session identifier, an identifier of the Qos flow in the PDU session, and downlink data forwarding proposed for the Qos flow. The eNB obtains the PDU session identifier corresponding to the EPS bearer and / or the Qos flow identifier in the PDU session through the PDN connection establishment process or through the switching process. The Qos information of the mapped Qos flow may also be obtained. The eNB decides whether to propose data forwarding based on the mapping of the Qos flow from the E-RAB to the PDU session or from the E-RAB to the PDU session and the Qos information. The eNB may consider other factors such as whether there is buffered data to make a decision without affecting the main content of the present invention.

[0229] Step 802: MME sends a forward relocation request message to AMF. MME selects and finds AMF according to the identification information of the AMF to which the target NG-RAN node is connected contained in the handover requirement message. The message includes the identification of the target NG-RAN node, the source-to-target transparent transmitter and UE context information. The UE context information includes UE mobility management MM context information and session management context. The message includes the type of handover.

[0230] The MME sends a direct forwarding indication to the AMF. If the MME receives a direct data forwarding indication from the source E-UTRAN that is not feasible, the MME determines whether indirect data forwarding is feasible. The MME informs the AMF of whether direct data forwarding is or is not. The MME may also inform the AMF of the information that data forwarding is not feasible, where the data forwarding not feasible means that both direct data forwarding and indirect data forwarding are not feasible.

[0231] Step 803a, AMF sends a Create Session (SM) Context Request message to SMF. AMF converts the received EPS UE context into a 5GS UE context. AMF can also exchange with PCRF to obtain the converted 5GS UE context. AMF selects the SMF that serves the UE.

[0232] According to the information received in the forwarding relocation request message, the AMF knows that the handover is between different systems, and the AMF requests the SMF to provide the SM context. The AMF sends the message to each SMF serving the UE.

[0233] AMF sends a direct forwarding indication to SMF, and AMF informs SMF of the available information of direct data forwarding or indirect data forwarding.

[0234] AMF informs SMF of whether direct data forwarding, indirect data forwarding, or data forwarding is not feasible.

[0235] Step 804, SMF initiates the N4 session modification process between SMF and UPF. SMF informs UPF of the information of direct data forwarding or indirect data forwarding. SMF can also inform UPF that data forwarding is not feasible. UPF informs SMF of the information supporting PDU session channel and / or E-RAB channel data forwarding. If direct data forwarding is feasible and UPF supports E-RAB channel data forwarding, UPF can inform SMF to support E-RAB channel data forwarding. If data forwarding is not feasible, UPF does not need to inform SMF which mode of data forwarding is supported. If indirect data forwarding is feasible, UPF informs SMF of the data forwarding mode it actually supports, such as information about PDU session channel and / or E-RAB channel data forwarding.

[0236] Step 803b, SMF sends a create session context response message to AMF. The message contains the SM context of the UE. The SM context also contains the mapping relationship between the EPS bearer and the QoS flow in the PDU session. If the SMF has a mapped EPS bearer context when the AMF requests the SM context, the SMF always feeds back the mapped EPS bearer context to the AMF at the same time. Or the SMF sends the mapped EPS bearer context to the AMF only when the AMF requests the mapped EPS context at the same time.

[0237] The 5GS UE context contains the QoS information in the 5G system. The QoS information in the 5G system contains QoS rules and / or QoS profiles. AMF can map EPS QoS information into 5G QoS information, or AMF interacts with the 5G Policy Control Function (5G-PCF) to derive 5G QoS information.

[0238] The SMF determines that direct data forwarding, indirect data forwarding or data forwarding is not feasible. If the direct forwarding received by the SMF indicates that direct data forwarding is feasible, the SMF may decide to use direct data forwarding. If the direct forwarding received by the SMF indicates indirect data forwarding and indirect data forwarding is feasible, the SMF decides to use indirect data forwarding. If the direct forwarding received by the SMF indicates indirect data forwarding but there is no indirect data forwarding connection, the SMF determines that data forwarding is not possible. The SMF includes the information that direct data forwarding, indirect data forwarding or data forwarding is not feasible in the N2 session management (SM) information container.

[0239] The message includes the data forwarding mode supported by UPF, that is, information that UPF supports PDU session channel and / or E-RAB channel data forwarding.

[0240] Step 805: AMF sends a handover request message to NG-RAN. The message contains information about the PDU session to be established. The PDU session information contains session identifier, session QoS information, QoS flow information, uplink channel information for each session, and / or source-to-destination transparent transmitter. The message contains the type of handover.

[0241] The message includes information about direct data forwarding, indirect data forwarding or data forwarding being impossible. The information may be included in an N2 SM information container.

[0242] The message includes the data forwarding mode supported by UPF, that is, information that UPF supports PDU session channel and / or E-RAB channel data forwarding.

[0243] The message may also include a mapping relationship between the Qos flow in the PDU session and the EPS bearer, that is, an E-RAB identifier mapped by the Qos flow and / or mapped Qos information.

[0244] Step 806: NG-RAN sends a handover request confirmation message to AMF. The message includes one or more of the following information: The transparent transmitter from the destination to the source may also include a mapping relationship between the Qos flow in the PDU session and the EPS bearer, that is, the EPS bearer identifier mapped by the Qos flow and / or the mapped Qos information.

[0245] The NG-RAN accepts the PDU session information list established. The PDU session information list includes the PDU session identifier, the downlink channel information of the NG3 interface used for the PDU session, the Qos flow information accepted by the PDU session, and the Qos flow information not accepted.

[0246] If NG-RAN and UPF support E-RAB channel data forwarding, for the QoS flow that NG-RAN accepts data forwarding or the E-RAB that accepts data forwarding, NG-RAN allocates downlink data forwarding channel information to the corresponding E-RAB, and includes the E-RAB identifier and the downlink channel information corresponding to the E-RAB allocated by NG-RAN in the handover request confirmation message. If NG-RAN and UPF support PDU session channel data forwarding, for the QoS flow that NG-RAN accepts data forwarding, NG-RAN allocates downlink data forwarding channel information to the PDU session to which it belongs, and includes the PDU session identifier and the downlink channel information corresponding to the PDU session allocated by NG-RAN in the handover request confirmation message, and may also include the Qosflow list that accepts data forwarding. If NG-RAN and UPF both support two data forwarding modes (PDU session channel data forwarding and E-RAB data forwarding mode), NG-RAN can decide which mode of data forwarding channel to allocate, and NG-RAN includes the corresponding data forwarding channel information in the handover request confirmation message. If data forwarding is not feasible, NG-RAN does not need to allocate data forwarding channel information. For direct data forwarding, only E-RAB channel data forwarding can be used, which is available when both NG-RAN and UPF support E-RAB channel data forwarding.

[0247] The NG-RAN does not accept the established PDU session information list. The PDU session information list includes the PDU session identifier and the reason for not accepting.

[0248] In step 807, AMF sends an update SM context request message to SMF. If channel information for data forwarding is received from NG-RAN, AMF sends the data forwarding channel information received from NG-RAN to SMF. AMF sends the channel information for data forwarding received from NG-RAN to SMF. AMF sends information on direct data forwarding or indirect data forwarding to SMF. AMF can inform SMF of direct data forwarding or indirect data forwarding in an explicit manner. AMF can also inform SMF in an implicit manner, that is, if SMF receives data forwarding channel information corresponding to each E-RAB, it is direct data forwarding, if it receives data forwarding channel information corresponding to each PDU session, it is indirect data forwarding, and if there is no data forwarding channel information, data forwarding is not feasible or data forwarding is not accepted by the destination base station. The message includes the PDU session to which the EPS bearer belongs. The message may also include a mapping relationship between the EPS bearer and the Qos flow in the PDU session.

[0249] Step 808, SMF initiates the session modification process between SMF and UPF. SMF sends information about direct data forwarding or indirect data forwarding to UPF. SMF sends the downlink data forwarding channel information of the NG3 interface allocated by NG-RAN to UPF through the N4 session modification process, and the data forwarding channel information is for each PDU session or each EPS bearer. SMF allocates data forwarding channel information between SGW and UPF, or UPF allocates channel information for data forwarding between SGW and UPF and sends it to SMF, and the data forwarding channel information is for each E-RAB. The N4 session modification message includes the PDU session to which the EPS bearer belongs. The N4 session establishment or N4 session modification message may also include a mapping relationship between the EPS bearer and the Qos flow in the PDU session. For direct data forwarding, SMF or UPF does not need to allocate data forwarding channel information. According to the information received in step 803 or this step, UPF knows whether it is direct data forwarding or indirect data forwarding. Corresponding to the implicit method, if SMF receives the data forwarding channel information for each E-RAB, it is direct data forwarding.

[0250] Step 809, SMF sends an update SM context response message to AMF. SMF sends the channel information used for data forwarding to AMF. For direct data forwarding, SMF sends the channel information corresponding to each E-RAB received from AMF to AMF, and the channel information corresponding to each E-RAB is allocated by the destination NG-RAN. For indirect data forwarding, SMF sends the channel information of each E-RAB allocated by SMF or UPF to AMF, and the channel information is used for data forwarding between SGW and UPF.

[0251] Step 810: AMF sends a forwarding relocation response message to MME. The message contains data forwarding channel information. For direct data forwarding, the channel information is allocated by the destination NG-RAN. For indirect data forwarding, the channel information is the channel information received from SMF for data forwarding between SGW and UPF. The message contains a transparent transmitter from the destination to the source.

[0252] Step 811, if the MME receives the channel information for data forwarding, for indirect data forwarding, the MME sends a create indirect data forwarding channel request message to the SGW. The message is used to send the channel information for data forwarding between the SGW and the UPF to the SGW. The SGW sends a create indirect data forwarding channel response message to the MME. The message contains the uplink channel information allocated by the SGW for S1 interface data forwarding. For direct data forwarding, this step does not need to be performed.

[0253] Step 812: MME sends a handover command message to E-UTRAN, wherein the message includes a transparent transmitter from the destination to the source, and the handover type.

[0254] The message includes data forwarding channel information. For indirect data forwarding, the channel information is allocated by the SGW. For direct data forwarding, the channel information is allocated by the destination NG-RAN.

[0255] Step 813: E-UTRAN sends a handover command message to the UE.

[0256] The message may also include a mapping relationship between the Qos flow and the EPS bearer in the PDU session, that is, the EPS bearer identifier mapped by the Qos flow and / or the mapped Qos information.

[0257] E-UTRAN forwards the data. For the E-RAB that receives the data forwarding channel, it means that the destination base station has accepted the data forwarding, and E-UTRAN forwards the data to the corresponding channel. For direct data forwarding, the destination NG-RAN directly receives the data forwarded by E-UTRAN. For indirect data forwarding, SGW receives the data forwarded by E-UTRAN. SGW forwards the data to UPF. SGW forwards the data to UPF on the corresponding channel for each EPS bearer that requires data forwarding. UPF forwards the data to NG-RAN. According to the data forwarding channel information allocated by NG-RAN received in step 808, UPF forwards the data to NG-RAN through the corresponding channel. If the received channel is for each PDU session, UPF sends the data belonging to the same PDU session received from the SGW corresponding to each EPS bearer channel to NG-RAN through the PDU session channel, that is, UPF maps multiple channels to one channel, and UPF forwards data to NG-RAN according to the session transmission method in 5GS. For example, each PDU session sends downlink data through several Qosflows, how to set the Qos flow header, UPF adds the Qos flow identifier (QFI) in the data packet header forwarded to the destination NG-RAN. If the received channel is for each E-RAB, UPF directly forwards the data to the corresponding E-RAB channel.

[0258] NG-RAN receives the forwarded data from the PDU session channel, and NG-RAN sends the received data to the UE in the existing manner. NG-RAN receives the forwarded data from the E-RAB channel, and NG-RAN does not need to process the SDAP layer, and directly sends the data to the PDCP layer of the corresponding DRB. Based on the mapping relationship between the E-RAB ID(s) and the Qos Flow ID(s) received in the handover request message, NG-RAN knows the DRB corresponding to the E-RAB, and thus directly sends the received forwarded data to the PDCP entity of the corresponding DRB. NG-RAN first sends the forwarded data to the UE, and then sends the data received from the new NG-U to the UE.

[0259] During the PDU session establishment or EPS bearer establishment process, the UE receives the QoS information and / or QoS flow information of the QoS flow mapped by the EPS bearer from the network. The UE associates the correspondence between the ongoing EPS bearer and the QoS flow contained in the handover command message. For EPS bearers that do not have a corresponding QoS flow, the UE can delete them.

[0260] Or the UE obtains the mapping relationship between the QoS flow in the PDU session and the EPS bearer from the handover command message. The UE associates the ongoing EPS bearer with the corresponding relationship between the QoS flow contained in the handover command message. For the EPS bearer without corresponding QoS flow, the UE can delete it.

[0261] Step 814: The UE sends a handover complete message to the NG-RAN.

[0262] Step 815: NG-RAN sends a handover notification message to AMF, wherein the message includes information about the channel allocated by NG-RAN for downlink data transmission.

[0263] Step 816, AMF sends an update SM context request message to SMF.

[0264] Step 817: SMF sends an N4 session modification message to UPF. UPF sends an N4 session modification response message to SMF.

[0265] AMF sends the channel information of downlink data transmission allocated by NG-RAN to UPF through AMF.

[0266] Step 818, SMF sends an update SMF context response message to AMF.

[0267] So far, the description of switching method four of the present invention is completed. This method can completely solve the problem of data forwarding when the UE moves between the EPS and 5GS systems when the data forwarding methods supported by devices from different manufacturers in the network are different, avoid data loss, ensure business continuity, ensure interoperability between devices from different manufacturers, and reduce the configuration of operators.

[0268] The present invention supports switching method 5 such as Fig. 9 As shown. The method is applicable to mode 3 where two data forwarding methods coexist, that is, both data forwarding methods must be supported. The method is used for switching from 5GS to EPS. Detailed descriptions of steps not related to the present invention are omitted here. The method includes the steps of: Step 901, NG-RAN decides to hand over the UE to E-UTRAN.

[0269] Here, E-UTRAN can be an eNB connected to EPC. NG-RAN can be a gNB or an eNB connected to 5GC or a centralized unit CU in a gNB.

[0270] The user plane path before handover is from UPF to NG-RAN. SGW needs to support the interface with UPF. UPF can include the functions of PGW user plane and perform the functions of user plane anchor point during handover between different RATs.

[0271] The UE has one or more PDU sessions in progress. Each PDU session contains one or more QoS flows. During the PDU session establishment or guaranteed service rate (GBR) QoS flow establishment process, the mapped EPS QoS information and / or EPS bearer identifier are allocated to the QoS flow. The non-guaranteed service rate (non-GBR) QoS flow is mapped to the default EPS bearer. The GBR QoS flow is mapped to the EPS dedicated bearer. The EPS QoS information mapped by the QoS flow can be allocated by the PCC or SMF. The EPS bearer identifier mapped by the QoS flow can be allocated by the SMF or AMF. In order to support switching between different systems, the SMF can also have the function of the PGW control plane. In the scenario of PCC deployment, the policy control function (PCF) provides the EPS QoS mapped by the QoS flow to the SMF. In order to support switching between different systems, the PCF can also have a policy control and charging function (PCRF). The SMF sends the EPS QoS information and / or EPS bearer identifier mapped by the QoS flow to the UE through the AMF, for example, through the non-access layer message PDU session establishment message to the UE. During the PDU session establishment or guaranteed service rate (GBR) QoS flow establishment process, SMF can also send EPS QoS information and / or E-RAB identifier mapped by QoS flow to NG-RAN through AMF. AMF sends EPS QoS information and / or E-RAB identifier mapped by QoS flow to NG-RAN through initial context establishment request message or PDU session resource establishment request message. NG-RAN can send EPS QoS information and / or E-RAB identifier mapped by QoS flow to UE through RRC message. E-RAB and EPS bearer identifiers are the same or have one-to-one correspondence. In the core network, it is EPS bearer, and in the access network, it is called E-RAB. The E-RAB identifier and EPS bearer identifier are the same or have one-to-one correspondence. In the core network, it is EPS bearer identifier, and in the access network, it is called E-RAB identifier.

[0272] In step 902, NG-RAN sends a switching request message to AMF. The message includes the identifier of the target eNB and the transparent transmitter from the source to the target. The transparent transmitter from the source to the target includes the E-RAB identifier and the downlink data forwarding proposed for this E-RAB. NG-RAN obtains the EPS bearer identifier mapped by the Qos flow in the PDU session through the PDU session establishment process or through the switching process. The mapped EPS Qos information may also be obtained. NG-RAN decides whether to propose data forwarding based on the mapping of the Qos flow to the E-RAB and the Qos information. NG-RAN can consider other factors such as whether there is buffered data to make a decision without affecting the main content of the present invention. The message includes information that a direct data forwarding path is available.

[0273] The message also includes identification information indicating the MME to which the target eNB is connected. The identification information may be a tracking area identification or an MME identification.

[0274] The message also contains the type of handover.

[0275] Step 903a, AMF sends a session management SM context request message to SMF. Based on the information received in the handover requirement message, AMF knows that the handover is between different systems, and AMF requests SMF to provide SM context. AMF can also request EPS bearer context. AMF sends the message to each SMF serving the UE. The message contains information that the direct data forwarding path is available. SMF saves information on whether direct data forwarding is feasible.

[0276] Step 903b, SMF sends an N4 session modification request message to UPF. The message contains information about the availability of the direct data forwarding path. UPF saves information about whether direct data forwarding is feasible. UPF sends an N4 session modification response message to SMF.

[0277] Step 903c, SMF sends an SM context response message to AMF. The message contains the SM context of the UE. The SM context also contains the mapped EPS bearer context, such as the EPS bearer identifier and / or EPS QoS information. If there is a mapped EPS bearer context when AMF requests the SM context, SMF always feeds back the mapped EPS bearer context to AMF at the same time. Or when AMF requests the SM context from SMF, it also indicates the requested mapped EPS bearer context. SMF sends the mapped EPS bearer context to AMF only when AMF requests the mapped EPS context at the same time.

[0278] Step 904, AMF sends a forward relocation request message to MME. AMF selects and finds MME according to the identification information of the MME to which the target eNB is connected contained in the handover requirement message. The identification information of the MME to which the target eNB is connected may be TAI. The message includes the identification of the target eNB, the source-to-target transparent transmitter and the mapped EPS UE context information. The mapped EPS UE context information includes UE mobility management MM context information and session SM context information.

[0279] If the AMF does not receive information from the source NG-RAN that direct data forwarding is available, the AMF determines whether indirect data forwarding is possible. If direct data forwarding is possible, direct data forwarding is used. The AMF informs the MME whether direct data forwarding or indirect data forwarding is used. The AMF may also inform the MME that data forwarding is not possible.

[0280] Step 905: MME sends a create session request message to SGW, wherein the message includes EPS bearer context information.

[0281] Step 906: SGW sends a create session response message to MME, wherein the message includes the channel information of the S1 interface allocated by SGW for uplink data transmission.

[0282] Step 907, MME sends a handover request message to E-UTRAN. The message includes a transparent transmitter from source to destination and an E-EAB context. The E-RAB context includes the uplink channel information of the E-RAB to be established and the S1 interface allocated by the SGW. The E-RAB context includes information on whether data forwarding is feasible. The message includes a handover type, and the specific content is the same as in step 902, which will not be repeated here.

[0283] Step 908: E-UTRAN sends a handover request confirmation message to MME. The message includes a list of established E-RABs and a list of failed established E-RABs, and a transparent transmitter from the destination to the source. For the established RAB, it also includes the channel information for downlink data transmission on the S1 interface. For the established E-RAB, if the source eNB proposes downlink data forwarding, data forwarding is feasible, and the target eNB accepts downlink data forwarding, the target eNB includes the channel information for data forwarding allocated by E-UTRAN for each E-RAB that needs downlink data forwarding.

[0284] Step 909, MME requests SGW to create an indirect data forwarding channel. This step is performed only when indirect data forwarding needs to be performed. If MME receives downlink channel information for data forwarding from E-UTRAN, MME requests SGW to create an indirect data forwarding channel. MME sends the transport layer address and TEID for data forwarding allocated by eNB to SGW. The transport layer address and TEID correspond to each E-RAB.

[0285] SGW sends an indirect data forwarding channel creation response message to MME. The message includes information allocated by SGW for data forwarding between SGW and UPF. The information used for data forwarding between SGW and UPF includes E-RAB identification and channel information used by the E-RAB for data forwarding. The channel information includes the transport layer address and TEID allocated by SGW. SGW allocates downlink data forwarding channel information to the E-RAB that needs downlink data forwarding. SGW allocates uplink data forwarding channel information to the E-RAB that needs uplink data forwarding. The data forwarding channel information included in the E-RAB information may include uplink and / or downlink data forwarding channel information.

[0286] When indirect data forwarding is feasible, step 909 is performed.

[0287] Step 910, MME sends a forwarding relocation response message to AMF. The message includes channel information for data forwarding. For direct data forwarding, the data forwarding channel information is received by MME from the destination base station. For indirect data forwarding, the channel information is the SGW allocation received by MME from SGW. The channel information is for each EPS bearer. The data forwarding channel information may include downlink and / or uplink data forwarding channel information. The message includes a transparent transmitter from the destination to the source.

[0288] MME directly sends the E-RAB information to AMF, which then converts it.

[0289] Step 911, AMF sends an update SM context request message to SMF. The message contains information about direct data forwarding or indirect data forwarding. AMF requests SMF to create a data forwarding channel. For indirect data forwarding, AMF requests SMF to create a data forwarding channel. The message contains PDU session information. The PDU session information contains the PDU session identifier, the QoS flow information contained in the PDU session, how many EPS bearers needing data forwarding in each PDU session in the EPS system, the mapping relationship between the QoS flow and the EPS bearer, the EPS bearer identifier and / or the QoS information of the EPS bearer. The message contains the channel information for data forwarding received from the MME.

[0290] Step 912, SMF sends an N4 session modification message to UPF. The message contains PDU session information. The PDU session information contains the PDU session identifier, the information of the QoS flow contained in the PDU session, the number of EPS bearers that need data forwarding in each PDU session in the EPS system, the mapping relationship between the QoS flow and the EPS bearer, the EPS bearer identifier and / or the QoS information of the EPS bearer. The message contains the channel information for data forwarding received from the AMF. The message contains information about direct data forwarding or indirect data forwarding.

[0291] The N4 session modification message includes the EPS bearer information included in the PDU session. The EPS bearer information includes the EPS bearer identifier and the channel information used by the EPS bearer for data forwarding. SMF informs UPF of the correspondence between the Qos flow and the EPS bearer in the PDU session. UPF knows the Qos flow information of the PDU session in the 5G system. UPF receives the EPS bearer information contained in the PDU session and the mapping relationship between the Qos flow and the EPS bearer from SMF.

[0292] UPF determines whether the data forwarding channel between the NG-RAN node and the UPF is the PDU session channel or the E-RAB channel. UPF allocates channel information for data forwarding between NG-RAN and UPF and sends it to SMF. If it is decided to use the data forwarding of the PDU session channel, the UPF allocates data forwarding channel information for the PDU session corresponding to the EPS bearer receiving data forwarding. If it is decided to use the data forwarding of the E-RAB channel, the UPF allocates data forwarding channel information for the EPS bearer receiving data forwarding. The channel information includes the transport layer address and TEID.

[0293] UPF sends the allocated channel information for data forwarding to SMF. SMF receives the N4 session modification response message from UPF. The message contains the channel information allocated by UPF for data forwarding between NG-RAN and UPF. For direct data forwarding, UPF does not need to allocate data forwarding channel information. Based on the information received in step 903 or this step, UPF knows whether it is direct data forwarding or indirect data forwarding. For direct data forwarding, step 912 may not be performed.

[0294] Step 913, SMF sends an update SM context response message to AMF. For direct data forwarding, the message includes the channel information for data forwarding received by SMF from AMF. The channel information is used for direct data forwarding, and the channel information is for each EPS bearer. For indirect data forwarding, the message includes the channel information allocated by UPF for data forwarding between NG-RAN and UPF. The channel information can be for each PDU session or each E-RAB.

[0295] Step 914, AMF sends a switching command message to NG-RAN. The message includes the channel information for data forwarding allocated by the destination to source transparent transmitter, E-UTRAN or UPF. The channel information for data forwarding corresponds to each PDU session or each E-RAB. For direct data forwarding, the channel information for data forwarding is for each E-RAB that accepts data forwarding. For indirect data forwarding, the channel information for data forwarding is for the PDU session to which each QoS flow that accepts data forwarding belongs. The message also includes the established PDU session information and the PDU session information that was not successfully established. The established PDU session information includes the established QoS flow information and the QoS flow information that was not successfully established.

[0296] Step 915: NG-RAN sends a handover command message to the UE.

[0297] NG-RAN forwards data.

[0298] If NG-RAN receives the data forwarding channel information corresponding to each PDU session, NG-RAN forwards the data to UPF. NG-RAN forwards the data to UPF on the channel corresponding to the PDU session for the Qos flow that requires data forwarding. NG-RAN sends the data of each Qos flow to UPF on the user plane channel allocated for the PDU session. For downlink data, NG-RAN sends the downlink data packet to UPF on the channel allocated for downlink data forwarding. UPF forwards the data to SGW. UPF adds the QFI corresponding to the Qos flow to the data packet header and forwards the data received from NG-RAN to SGW through the user plane channel allocated for the corresponding EPS bearer. UPF forwards the data of different Qos flows in the PDU session to SGW through the user plane channel allocated for the corresponding EPS bearer based on the mapping relationship between Qos flow and EPS bearer. Based on the mapping relationship between Qos flow and EPS bearer and the EPS bearer information that accepts data forwarding, UPF knows the Qos flow that accepts data forwarding, and UPF forwards the data of the Qos flow that accepts data forwarding to the user plane channel allocated for the corresponding EPS bearer and forwards it to SGW. For the QoS flow that does not accept data forwarding, there is no corresponding data forwarding channel, and the UPF discards the data.

[0299] If NG-RAN receives the data forwarding channel information corresponding to each E-RAB, NG-RAN forwards the Qos flow data to the corresponding E-RAB channel. NG-RAN forwards the PDCP SDU to the corresponding E-RAB channel. The PDCP SDU does not carry a SN. For indirect data forwarding, the data is sent to the UPF, and the UPF forwards the data to the SGW. For direct data forwarding, the data is sent directly to the destination base station.

[0300] SGW forwards data to E-UTRAN. SGW sends the data received from UPF corresponding to each EPS bearer channel to E-UTRAN through the corresponding channel allocated by E-UTRAN. SGW forwards data to E-UTRAN according to the session transmission mode in EPS.

[0301] E-UTRAN receives the forwarded data from the E-RAB channel. E-UTRAN first sends the forwarded data to the UE, and then sends the data received from the new S1-U to the UE.

[0302] During the PDU session establishment or GBR QoS flow establishment process, the UE receives the EPS QoS information and / or EPS bearer identification information mapped by the QoS flow from the network. The UE associates the ongoing QoS flow with the EPS bearer identification contained in the handover command message. For QoS flows that do not have a corresponding EPS bearer, the UE can delete them.

[0303] Step 916: The UE sends a handover complete message to the E-UTRAN.

[0304] Step 917: E-UTRAN sends a handover notification message to MME, wherein the message includes information about the channel allocated by E-UTRAN for downlink data transmission.

[0305] Step 918: MME sends a modify bearer request message to SGW, wherein the message includes channel information of the S1 interface used for downlink data transmission.

[0306] Step 919, SGW sends a modify bearer request message to SMF. SMF may also have a PGW control plane function. SGW allocates channel information for downlink data transmission between SGW and UPF, and the channel information corresponds to each EPS bearer or each PDU session.

[0307] Step 920, SMF requests UPF to modify the session. SMF may also have the function of PGW control plane. SMF sends the channel information for downlink data transmission between SGW and UPF allocated by SGW to UPF, and the channel information corresponds to each EPS bearer or each PDU session. UPF sends a session modification response to SMF. UPF allocates the channel information for uplink data transmission between SGW and UPF, and UPF sends the channel information for uplink data transmission to SMF.

[0308] Step 921, SMF sends a modify bearer response message to SGW. The message includes the channel information between SGW and UPF for uplink data transmission allocated by UPF.

[0309] Step 922: SGW sends a modify bearer response message to MME.

[0310] So far, the description of switching method five of the present invention is completed. This method can completely solve the problem of data forwarding when the UE moves between the EPS and 5GS systems when the data forwarding methods supported by devices from different manufacturers in the network are different, avoid data loss, ensure business continuity, ensure interoperability between devices from different manufacturers, and reduce the configuration of operators.

[0311] The present invention supports the switching method six as follows Fig.10As shown. The method is applicable to mode 3 where two data forwarding methods coexist, that is, both data forwarding methods must be supported. The method is used for switching from EPS to 5GS. Detailed descriptions of steps not related to the present invention are omitted here. The method includes the steps of: Step 1000, E-UTRAN decides to hand over the UE to NG-RAN.

[0312] The E-UTRAN here can be an eNB connected to the EPC. The NG-RAN can be a gNB or an eNB connected to the 5GC or a centralized unit CU in the gNB. The eNB connected to the 5GC can also be called an ng-eNB.

[0313] The user plane path before switching is PGW-U+UPF (UPF has PGW user plane function, hereinafter referred to as UPF), SGW to E-UTRAN. SGW needs to support the interface with PGW-U+UPF. UE has one or more PDU sessions in progress. Each PDU session contains one or more EPS bearers. During the PDU session establishment or EPS bearer establishment process, the EPS bearer is allocated QoS information and / or QoS flow identifier of the mapped QoS flow. The default EPS bearer is mapped to the non-guaranteed service rate (non-GBR) QoS flow. The QoS information and / or QoS flow identifier of the QoS flow mapped by the EPS bearer can be allocated by the PCC or PGW control plane function. In order to support switching between different systems, the PGW control plane function can also have SMF function. In the scenario of PCC deployment, the policy control and charging function (PCRF) provides the QoS and / or QoS flow identifier of the QoS flow mapped by the EPS bearer to the SMF. In order to support switching between different systems, there is also a policy control function (PCF) on the PCRF. SMF sends the QoS and / or QoS flow identifier of the QoS flow mapped by the EPS bearer to the UE through the MME, for example, through the non-access layer message PDN connection establishment message to the UE. During the PDU session establishment or EPS bearer establishment process, SMF can also send the QoS and / or QoS flow identifier of the QoS flow mapped by the EPS bearer to the E-UTRAN through the MME. E-UTRAN can send the mapping information to the UE through an RRC message. The E-RAB and EPS bearer identifiers are the same or have a one-to-one correspondence. In the core network, it is an EPS bearer, and in the access network, it is called an E-RAB. The E-RAB identifier and the EPS bearer identifier are the same or have a one-to-one correspondence. In the core network, it is an EPS bearer identifier, and in the access network, it is called an E-RAB identifier.

[0314] Step 1001, E-UTRAN sends a handover requirement message to MME. The message includes the identifier of the target NG-RAN node and the transparent transmitter from the source to the target. The message also includes the identifier information indicating the AMF to which the target NG-RAN node is connected. The identifier information may be a tracking area identifier, a network slice identifier, an AMF pool identifier, or an AMF identifier, etc.

[0315] The message contains information that a direct data forwarding path is available.

[0316] The source-to-destination transparent transmitter includes a PDU session identifier, an identifier of the Qos flow in the PDU session, and downlink data forwarding proposed for the Qos flow. The eNB obtains the PDU session identifier corresponding to the EPS bearer and / or the Qos flow identifier in the PDU session through the PDN connection establishment process or through the switching process. The Qos information of the mapped Qos flow may also be obtained. The eNB decides whether to propose data forwarding based on the mapping of the Qos flow from the E-RAB to the PDU session or from the E-RAB to the PDU session and the Qos information. The eNB may consider other factors such as whether there is buffered data to make a decision without affecting the main content of the present invention.

[0317] Step 1002, MME sends a forward relocation request message to AMF. MME selects and finds AMF according to the identification information of the AMF to which the target NG-RAN node is connected contained in the handover requirement message. The message includes the identification of the target NG-RAN node, the source-to-target transparent transmitter and UE context information. The UE context information includes UE mobility management MM context information and session management context. The message includes the type of handover.

[0318] The MME sends a direct forwarding indication to the AMF. If the MME receives a message from the source E-UTRAN that direct data forwarding is not feasible, the MME decides whether indirect data forwarding is feasible. The MME informs the AMF of whether direct data forwarding is or is not. The MME can also inform the AMF of the information that data forwarding is not feasible. The data forwarding not feasible means that both direct data forwarding and indirect data forwarding are not feasible. Alternatively, the MME sends information that direct data forwarding is available to the AMF.

[0319] Step 1003a, AMF sends a Create Session (SM) Context Request message to SMF. AMF converts the received EPS UE context into a 5GS UE context. AMF can also exchange with PCRF to obtain the converted 5GS UE context. AMF selects the SMF that serves the UE.

[0320] According to the information received in the forwarding relocation request message, the AMF knows that the handover is between different systems, and the AMF requests the SMF to provide the SM context. The AMF sends the message to each SMF serving the UE.

[0321] AMF sends a direct forwarding indication to SMF, and AMF informs SMF of the available information of direct data forwarding or indirect data forwarding.

[0322] AMF informs SMF of direct data forwarding, indirect data forwarding, or information that data forwarding is not feasible. AMF can also inform SMF of information that direct data forwarding is available.

[0323] Step 1004, SMF initiates the N4 session modification process with UPF. SMF informs UPF of the information of direct data forwarding or indirect data forwarding. SMF may also inform UPF of the information that data forwarding is not feasible. SMF may also inform UPF of the information that direct data forwarding is available.

[0324] Step 1003b, SMF sends a create session context response message to AMF. The message contains the SM context of the UE. The SM context also contains the mapping relationship between the EPS bearer and the QoS flow in the PDU session. If the SMF has a mapped EPS bearer context when the AMF requests the SM context, the SMF always feeds back the mapped EPS bearer context to the AMF at the same time. Or the SMF sends the mapped EPS bearer context to the AMF only when the AMF requests the mapped EPS context at the same time.

[0325] The 5GS UE context contains the QoS information in the 5G system. The QoS information in the 5G system contains QoS rules and / or QoS profiles. AMF can map EPS QoS information into 5G QoS information, or AMF interacts with the 5G Policy Control Function (5G-PCF) to derive 5G QoS information.

[0326] SMF decides that direct data forwarding, indirect data forwarding or data forwarding is not feasible. If the direct forwarding received by SMF indicates that direct data forwarding is feasible, SMF may decide to adopt direct data forwarding. If the direct forwarding received by SMF indicates indirect data forwarding and indirect data forwarding is feasible, SMF decides to adopt indirect data forwarding. If the direct forwarding received by SMF indicates indirect data forwarding but there is no indirect data forwarding connection, SMF decides that data forwarding is not possible. SMF includes information that direct data forwarding, indirect data forwarding or data forwarding is not feasible in the N2 session management (SM) information container. The direct data forwarding information may be information that direct data forwarding is available. The fact that data forwarding is not feasible means that indirect data forwarding is not feasible or both direct and indirect data forwarding are not feasible.

[0327] SMF determines that indirect data forwarding or data forwarding is not feasible. SMF informs the target NG-RAN of the information. Or, The SMF determines whether indirect data forwarding is not feasible. The SMF informs the destination NG-RAN of the information that indirect data forwarding is not feasible and whether direct data forwarding is available.

[0328] Step 1005, AMF sends a handover request message to NG-RAN. The message contains information about the PDU session to be established. The PDU session information contains session identifier, session QoS information, QoS flow information, uplink channel information of each session, and / or transparent transmitter from source to destination. The message contains the type of handover.

[0329] The message includes information that direct data forwarding, indirect data forwarding or data forwarding is impossible. The information may be included in the N2 SM information container. The direct data forwarding information may be information that direct data forwarding is available. The impossibility of data forwarding means that indirect data forwarding is not feasible or both direct and indirect data forwarding are not feasible. The message may also include a mapping relationship between the QoS flow in the PDU session and the EPS bearer, i.e., the E-RAB identifier of the QoS flow mapping and / or the mapped QoS information.

[0330] Step 1006: NG-RAN sends a handover request confirmation message to AMF. The message includes one or more of the following information: The transparent transmitter from the destination to the source may also include a mapping relationship between the Qos flow in the PDU session and the EPS bearer, that is, the EPS bearer identifier mapped by the Qos flow and / or the mapped Qos information.

[0331] The NG-RAN accepts the PDU session information list established. The PDU session information list includes the PDU session identifier, the downlink channel information of the NG3 interface used for the PDU session, the Qos flow information accepted by the PDU session, and the Qos flow information not accepted.

[0332] NG-RAN decides whether the data forwarding channel is the channel corresponding to each PDU session or the channel corresponding to each E-RAB. If direct data forwarding is feasible, NG-RAN can decide to use the E-RAB channel for data forwarding, and include the E-RAB identifier and the downlink channel information corresponding to the E-RAB allocated by NG-RAN in the switching request confirmation message. If it is indirect data forwarding, NG-RAN decides whether the channel used for data forwarding between NG-RAN and UPF is the channel corresponding to each PDU session or the channel corresponding to each E-RAB. If it is decided to use the data forwarding of the PDU session channel, NG-RAN allocates data forwarding channel information to the PDU session to which the Qosflow that accepts data forwarding belongs, and includes the PDU session identifier and the downlink channel information corresponding to the PDU session allocated by NG-RAN in the switching request confirmation message, and may also include a list of Qosflows that accept data forwarding. If it is decided to use the data forwarding of the E-RAB channel, the NG-RAN allocates data forwarding channel information to the E-RAB corresponding to the QoS flow or E-RAB that receives the data forwarding, and includes the E-RAB identifier and the downlink channel information corresponding to the E-RAB allocated by the NG-RAN in the switching request confirmation message. The channel information includes the transport layer address and TEID. The NG-RAN sends the allocated data forwarding channel information to the AMF. If data forwarding is not feasible, the NG-RAN does not need to allocate data forwarding channel information. For direct data forwarding, only E-RAB channel data forwarding can be used.

[0333] The NG-RAN does not accept the established PDU session information list. The PDU session information list includes the PDU session identifier and the reason for not accepting.

[0334] Step 1007, AMF sends an update SM context request message to SMF. If the channel information for data forwarding is received from NG-RAN, AMF sends the data forwarding channel information received from NG-RAN to SMF. AMF sends the channel information for data forwarding received from NG-RAN to SMF. AMF sends information about direct data forwarding or indirect data forwarding to SMF. AMF can inform SMF in an explicit manner whether direct data forwarding, indirect data forwarding or data forwarding is not feasible. AMF can also inform SMF in an implicit manner whether direct data forwarding or indirect data forwarding is feasible, that is, if the channel used for data forwarding is that of a PDU session, it is indirect data forwarding, and if it is the channel information of an EPS bearer, it is direct data forwarding. If there is no data forwarding channel information, data forwarding is not feasible or data forwarding is not accepted by the destination base station. The message includes the PDU session to which the EPS bearer belongs. The message may also include a mapping relationship between the EPS bearer and the Qos flow in the PDU session.

[0335] Step 1008, SMF initiates the session modification process between SMF and UPF. SMF sends information about direct data forwarding or indirect data forwarding to UPF. SMF sends the NG3 interface downlink data forwarding channel information allocated by NG-RAN to UPF through the N4 session modification process, and the data forwarding channel information is for each PDU session or each EPS bearer. SMF allocates data forwarding channel information between SGW and UPF, or UPF allocates channel information for data forwarding between SGW and UPF and sends it to SMF, and the data forwarding channel information is for each E-RAB. The N4 session modification message includes the PDU session to which the EPS bearer belongs. The N4 session establishment or N4 session modification message may also include a mapping relationship between the EPS bearer and the Qos flow in the PDU session. For direct data forwarding, SMF or UPF does not need to allocate data forwarding channel information. According to the information received in step 1003 or this step, UPF knows whether it is direct data forwarding or indirect data forwarding. Corresponding to the implicit method, if SMF receives the data forwarding channel information for each E-RAB, it is direct data forwarding.

[0336] Step 1009, SMF sends an update SM context response message to AMF. SMF sends the channel information used for data forwarding to AMF. For direct data forwarding, SMF sends the channel information corresponding to each E-RAB received from AMF to AMF, and the channel information corresponding to each E-RAB is allocated by the destination NG-RAN. For indirect data forwarding, SMF sends the channel information of each E-RAB allocated by SMF or UPF to AMF, and the channel information is used for data forwarding between SGW and UPF.

[0337] Step 1010, AMF sends a forwarding relocation response message to MME. The message contains data forwarding channel information. For direct data forwarding, the channel information is allocated by the destination NG-RAN. For indirect data forwarding, the channel information is the channel information received from SMF for data forwarding between SGW and UPF. The message contains a transparent transmitter from the destination to the source.

[0338] Step 1011, if the MME receives the channel information for data forwarding, for indirect data forwarding, the MME sends a request message for creating an indirect data forwarding channel to the SGW. The message is used to send the channel information for data forwarding between the SGW and the UPF to the SGW. The SGW sends a response message for creating an indirect data forwarding channel to the MME. The message includes the uplink channel information allocated by the SGW for S1 interface data forwarding. For direct data forwarding, this step does not need to be performed. The MME knows whether to forward data directly or indirectly based on the information on the available direct data forwarding path received from the source base station, as described in step 1002.

[0339] Step 1012: MME sends a handover command message to E-UTRAN, wherein the message includes a transparent transmitter from the destination to the source, and the handover type.

[0340] The message includes data forwarding channel information. For indirect data forwarding, the channel information is allocated by the SGW. For direct data forwarding, the channel information is allocated by the destination NG-RAN.

[0341] Step 1013: E-UTRAN sends a handover command message to the UE.

[0342] The message may also include a mapping relationship between the Qos flow and the EPS bearer in the PDU session, that is, the EPS bearer identifier mapped by the Qos flow and / or the mapped Qos information.

[0343] E-UTRAN forwards the data. For the E-RAB that receives the data forwarding channel, it means that the destination base station has accepted the data forwarding, and E-UTRAN forwards the data to the corresponding channel. For direct data forwarding, the destination NG-RAN directly receives the data forwarded by E-UTRAN. For indirect data forwarding, SGW receives the data forwarded by E-UTRAN. SGW forwards the data to UPF. SGW forwards the data to UPF on the corresponding channel for each EPS bearer that requires data forwarding. UPF forwards the data to NG-RAN. According to the data forwarding channel information allocated by NG-RAN received in step 1008, UPF forwards the data to NG-RAN through the corresponding channel. If the received channel is for each PDU session, UPF sends the data belonging to the same PDU session received from the SGW corresponding to each EPS bearer channel to NG-RAN through the PDU session channel, that is, UPF maps multiple channels to one channel, and UPF forwards data to NG-RAN according to the session transmission method in 5GS. For example, each PDU session sends downlink data through several Qosflows, how to set the Qos flow header, UPF adds the Qos flow identifier (QFI) in the data packet header forwarded to the destination NG-RAN. If the received channel is for each E-RAB, UPF directly forwards the data to the corresponding E-RAB channel.

[0344] NG-RAN receives the forwarded data from the PDU session channel, and NG-RAN sends the received data to the UE in the existing manner. NG-RAN receives the forwarded data from the E-RAB channel, and NG-RAN does not need to process the SDAP layer, and directly sends the data to the PDCP layer of the corresponding DRB. Based on the mapping relationship between the E-RAB ID(s) and the Qos Flow ID(s) received in the handover request message, NG-RAN knows the DRB corresponding to the E-RAB, and thus directly sends the received forwarded data to the PDCP entity of the corresponding DRB. NG-RAN first sends the forwarded data to the UE, and then sends the data received from the new NG-U to the UE.

[0345] During the PDU session establishment or EPS bearer establishment process, the UE receives the QoS information and / or QoS flow information of the QoS flow mapped by the EPS bearer from the network. The UE associates the correspondence between the ongoing EPS bearer and the QoS flow contained in the handover command message. For EPS bearers that do not have a corresponding QoS flow, the UE can delete them.

[0346] Or the UE obtains the mapping relationship between the QoS flow in the PDU session and the EPS bearer from the handover command message. The UE associates the ongoing EPS bearer with the corresponding relationship between the QoS flow contained in the handover command message. For the EPS bearer without corresponding QoS flow, the UE can delete it.

[0347] Step 1014: The UE sends a handover complete message to the NG-RAN.

[0348] Step 1015: NG-RAN sends a handover notification message to AMF, wherein the message includes channel information allocated by NG-RAN for downlink data transmission.

[0349] Step 1016, AMF sends an update SM context request message to SMF.

[0350] Step 1017, SMF sends an N4 session modification message to UPF. UPF sends an N4 session modification response message to SMF.

[0351] AMF sends the channel information of downlink data transmission allocated by NG-RAN to UPF through AMF.

[0352] Step 1018, SMF sends an update SMF context response message to AMF.

[0353] So far, the description of switching method six of the present invention is completed. This method can completely solve the problem of data forwarding when the UE moves between the EPS and 5GS systems when the data forwarding methods supported by devices from different manufacturers in the network are different, avoid data loss, ensure business continuity, ensure interoperability between devices from different manufacturers, and reduce the configuration of operators.

[0354] Based on the same inventive concept, an embodiment of the present application provides a device, which may be any of the above-mentioned devices, for example, one of a source base station, a source core network, a destination core network, a destination base station, a UPF, an SMF, an AMF, an NG-RAN node, etc. The device includes: a transceiver and a processor, The transceiver is used to send and receive signals; The processor is used to execute the method executed by any of the above-mentioned devices.

[0355] Based on the same inventive concept, an embodiment of the present application provides a computer-readable storage medium, on which a computer program is stored. When the program is executed by a processor, the method shown in Embodiment 7 is implemented.

[0356] Specifically, it will be understood by those skilled in the art that the present application includes devices for performing one or more of the operations described in the present application, including full-duplex transceivers and electronic devices. These devices may be specially designed and manufactured for the desired purpose, or may also include known devices in general-purpose computers. These devices have computer programs stored therein, which are selectively activated or reconstructed. Such computer programs may be stored in a device (e.g., computer) readable medium or in any type of medium suitable for storing electronic instructions and coupled to a bus, respectively, the computer readable medium including but not limited to any type of disk (including floppy disk, hard disk, optical disk, CD-ROM, and magneto-optical disk), ROM (Read-Only Memory), RAM (Random Access Memory), EPROM (Erasable Programmable Read-Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), flash memory, magnetic card or optical card. That is, the readable medium includes any medium that stores or transmits information in a readable form by a device (e.g., computer).

[0357] The present application embodiment provides a computer-readable storage medium applicable to the above method embodiment, which will not be described in detail here.

[0358] It should be understood that, although the steps in the flowchart of the accompanying drawings are displayed in sequence as indicated by the arrows, these steps are not necessarily executed in sequence in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least a part of the steps in the flowchart of the accompanying drawings may include multiple sub-steps or multiple stages, and these sub-steps or stages are not necessarily executed at the same time, but can be executed at different times, and their execution order is not necessarily sequential, but can be executed in turn or alternately with other steps or at least a part of the sub-steps or stages of other steps.

[0359] The above description is only a partial implementation method of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A method performed by a source base station in a wireless communication system, characterized in that: include: Sending a handover requirement message to the AMF, wherein the handover requirement message includes information that direct data forwarding is available; A switching command message is received from the AMF. When direct data forwarding is used, the switching command message includes information of the E-RAB for data forwarding accepted by the target base station.

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