Method for performing handover and related apparatuses

Abstract

A method for performing handover and related apparatuses are provided. The method by a source RAN node includes communicating a first handover (HO) required message with a source access and mobility management function (AMF) for the source AMF to select a target AMF, which determines a target RAN node based on the first HO required message; directly communicating a second HO required message with a session management function (SMF), wherein the second HO required message includes all or part of protocol data unit (PDU) session- related information for PDU session handover; and receiving a HO command message from the target RAN node to handover a user equipment (UE) to the target RAN node. The method can facilitate implementing a handover procedure in a communication system (e.g., 6G system) without relying on AMF as anchor.

Description

Atty. Dkt. No. 10085-01-0172-PCTMETHOD FOR PERFORMING HANDOVERAND RELATEDAPPARATUSESCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 63 / 702,631, entitled “METHOD AND APPARATUS OF PERFORMING USER EQUIPMENT (UE) HANDOVER IN 6G NETWORK WITH DISTRIBUTED NON-ACCESS STRATUM (NAS),” filed on October 2, 2024, which is hereby incorporated in its entirety by this reference.TECHNICAL FIELD

[0002] The present application relates to wireless communication technologies, and more particularly, to a method for performing handover and related apparatuses.BACKGROUND ART

[0003] In cellular wireless communication systems developed by the Third Generation Partnership Project (3GPP), user equipment (UE) is connected by a wireless link to a radio access network (RAN). The RAN includes a set of base stations (BSs) which provide wireless links to UEs located in cells covered by the base station and an interface to a core network (CN) which provides overall network control. The RAN and CN each conduct respective functions in relation to the overall network. The so-called 4G Long Term Evolution (LTE) system, namely, an Evolved Universal Mobile Telecommunication System Territorial Radio Access Network (E-UTRAN) has been developed for a mobile access network where one or more macro-cells are supported by a base station known as an eNodeB or eNB (evolved NodeB). Evolved from LTE, the so-called 5G or new radio (NR) systems where one or more cells are supported by a base station known as a gNB. Envisioned to succeed the current 5G networks, the 6G cellular system is the forthcoming generation of wireless communication technology.

[0004] In 5G networks, NAS (Non-Access Stratum) handles signaling between the User Equipment (UE) and the Core Network (CN), e.g., between the UE and the Access and Mobility Management Function (AMF). NAS messages are responsible for functions such as registration, mobility management, and session management. When the UE sends a NAS message (e.g., Registration Request or Session Management Request), the message is encapsulated within an RRC (Radio Resource Control) message and transmitted to the gNB (Next Generation Node B). The gNB, being transparent to NAS, forwards the NAS container to the AMF without processing its contents. Once the AMF receives the NAS message, it decodes and processes it. If the messageAtty. Dkt. No. 10085-01-0172-PCT is intended for the AMF itself, it manages tasks like registration and mobility. If the message is session-related (e.g., establishing a data session), the AMF forwards it to the appropriate CN entities, such as the SMF (Session Management Function). If the message is targeting other Network Functions (NF), the AMF forwards it to the corresponding NF. This NAS signaling allows the UE to communicate with different core network functions while enabling efficient mobility, session, and connection management in 5G.

[0005] The existing mechanism of NAS signaling relies on AMF as a single anchor point for the UE. All NAS messages are first sent to AMF for processing before next step of handling. In 6G network, it is expected more network functionalities will be introduced as new services to the UE. These new functionalities and some existing CN functions may be deployed closer to or together with RAN as an edge cloud. This is to localize critical signaling processing to reduce latency and improve performance. Therefore, it is desired to design a new NAS signaling transmission mechanism to allow the UE (via RAN) to directly communicate to individual CN functions. The concept is shown in FIG. 1. As shown in FIG. 1, the protocol stack at least includes a lower (physical) layer, a security enabling layer and a RRC layer. The UE implements a direct communication pathway to network functions with the CN via NAS messages.

[0006] In 5G network, when the UE performs handover, the AMF manages the UE mobility and coordinates the UE and the SMF to complete PDU session management. The UE uses the AMF as anchor point to complete all necessary procedures that involve CN NFs. With distributed NAS, the 6G RAN is able to directly communicate to SMF and other CN NFs.SUMMARY

[0007] An object of the present application is to propose a method for performing handover and related apparatuses, which can implement a handover procedure (with distributed NAS) without relying on AMF as anchor, reduce latency, enhance communication performance, and / or provide high reliability.

[0008] In a first aspect of the present application, provided is a method for performing handover, performed by a source radio access network (RAN) node, including communicating a first handover (HO) required message with a source access and mobility management function (AMF) for the source AMF to select a target AMF, which determines a target RAN node based on the first HO required message; directly communicating a second HO required message with a session management function (SMF), wherein the second HO required message includes all or part of protocol data unit (PDU) session-related information for PDU session handover; and receiving aAtty. Dkt. No. 10085-01-0172-PCTHO command message from the target RAN node to handover a user equipment (UE) to the target RAN node.

[0009] In a second aspect of the present application, provided is a method for performing handover, performed by a target radio access network (RAN) node, including communicating with a target access and mobility management function (AMF) to receive a first handover (HO) request message from the target AMF that is selected by a source AMF, wherein a source RAN node is determined by the target RAN node based on the first HO request message; directly communicating with a session management function (SMF) to receive a second HO request message from the SMF, wherein the second HO request message includes all or part of protocol data unit (PDU) session-related information for PDU session handover; and sending a HO command message to the source RAN node to handover a user equipment (UE) to the target RAN node.

[0010] In a third aspect of the present application, provided is a source radio access network (RAN) node, including at least one memory configured to store program instructions; and at least one processor configured to execute the program instructions, which cause the at least one processor to execute the corresponding method mentioned above.

[0011] In a fourth aspect of the present application, provided is a target radio access network (RAN) node, including at least one memory configured to store program instructions; and at least one processor configured to execute the program instructions, which cause the at least one processor to execute the corresponding method mentioned above.

[0012] In a fifth aspect of the present application, provided is a source radio access network (RAN) node, including a first communication module, configured to communicate a first handover (HO) required message with a source access and mobility management function (AMF) for the source AMF to select a target AMF, which determines a target RAN node based on the first HO required message; a second communication module, configured to directly communicate a second HO required message with a session management function (SMF), wherein the second HO required message includes all or part of protocol data unit (PDU) session-related information for PDU session handover; and a first receiving module, configured to receive a HO command message from the target RAN node to handover a user equipment (UE) to the target RAN node.

[0013] In a sixth aspect of the present application, provided is a target radio access network (RAN) node, including a third communication module, configured to communicate with a target access and mobility management function (AMF) to receive a first handover (HO) request message fromAtty. Dkt. No. 10085-01-0172-PCT the target AMF that is selected by a source AMF, wherein a source RAN node is determined by the target RAN node based on the first HO request message; a fourth communication module, configured to directly communicate with a session management function (SMF) to receive a second HO request message from the SMF, wherein the second HO request message includes all or part of protocol data unit (PDU) session-related information for PDU session handover; and a sending module, configured to send a HO command message to the source RAN node to handover a user equipment (UE) to the target RAN node.

[0014] In a seventh aspect of the present application, a non-transitory machine-readable storage medium has stored thereon instructions that, when executed by a computer, cause the computer to perform the above method.

[0015] In an eighth aspect of the present application, a chip includes a processor, configured to call and run a computer program stored in a memory, to cause a device in which the chip is installed to execute the above method.

[0016] In a ninth aspect of the present application, a computer readable storage medium, in which a computer program is stored, causes a computer to execute the above method.

[0017] In a tenth aspect of the present application, a computer program product includes a computer program, and the computer program causes a computer to execute the above method.

[0018] ‘In an eleventh aspect of the present application, a computer program causes a computer to execute the above method.DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present application or related art, the following figures that will be described in the embodiments are briefly introduced. It is obvious that the drawings are merely some embodiments of the present application, a person having ordinary skill in this field can obtain other figures according to these figures without paying the premise.

[0020] FIG. l is a schematic diagram illustrating a concept view of 6G NAS signaling without relying on AMF as anchor.

[0021] FIG. 2 is a schematic diagram illustrating a communication architecture according to an embodiment of the present application.

[0022] FIG. 3 is a flowchart of a method for performing handover implemented by a source RAN node according to an embodiment of the present application.Atty. Dkt. No. 10085-01-0172-PCT

[0023] FIG. 4 is a flowchart of a method for performing handover implemented by a target RAN node according to an embodiment of the present application.

[0024] FIG. 5 is a schematic diagram illustrating a call flow for performing handover according to an embodiment of the present application.

[0025] FIG. 6 is a block diagram of a source RAN node according to an embodiment of the present application.

[0026] FIG. 7 is a block diagram of a target RAN node according to an embodiment of the present application.DETAILED DESCRIPTION OF EMBODIMENTS

[0027] Embodiments of the disclosure are described in detail with the technical matters, structural features, achieved objects, and effects with reference to the accompanying drawings as follows. Specifically, the terminologies in the embodiments of the present application are merely for describing the purpose of the certain embodiment, but not to limit the disclosure.

[0028] In this document, the term “ / ” should be interpreted to indicate “and / or.” A combination such as “at least one of A, B, or C,” “one or more of A, B, or C,” “at least one of A, B, and C,” “one or more of A, B, and C,” or “A, B, and / or C” may be A only, B only, C only, A and B, A and C, B and C, or A and B and C, where any combination may contain one or more members of A, B, or C.

[0029] This application provides solutions to implement a handover procedure without relying on AMF as anchor. The radio access network (RAN) can directly communicate with AMF and SMF to complete the handover procedure with distributed NAS (Non-Access Stratum) messages.

[0030] FIG. 2 shows a communication architecture according to an embodiment of the present application. Devices involved in the communication architecture include, but are not limited to, a User Equipment (UE) 10, a Radio Access Network (RAN) node 20, an Access and Mobility Management Function (AMF) 30, a Session Management Function (SMF) 40, and a User Plane Function (UPF) 50. It is noted that the present application may be applicable to future communication system such as 6G system. The UE 10 may be an equipment with 3GPP communication capability, such as a smartphone, a tablet computer and etc. The RAN node 20 can be a base station or gNB. The AMF 30 is mainly responsible for executing access and UE mobility management tasks. The SMF 40 is mainly responsible for executing session management tasks. The UPF 50 plays a crucial role in the user plane architecture of the core network.Atty. Dkt. No. 10085-01-0172-PCT

[0031] With distributed NAS, the RAN node 20 is able to directly communicate with network functions (NFs) within core network (CN) using service-based architecture (SB A). As depicted in FIG. 2, the RAN node 20 is able to directly communicate with the AMF 30 and SMF 40. The RAN node 20 may also directly communicate with other CN NFs. The SBA designs core network functions as modular services communicating via Application Programming Interfaces (APIs), enabling flexible deployment and seamless integration with cloud computing to support diverse use cases like ultra-low latency, Internet of Things (loT), and immersive Extended Reality (XR).

[0032] According to the techniques of the present application, when a source RAN node decides to perform handover to a target RAN node for the UE, instead of relying on the AMF to coordinate the handover procedure with SMF, the RAN node(s) will (directly) communicate with the AMF and at the same time directly communicate with the SMF to complete the handover procedure.

[0033] In this design, it is preferred that both the source RAN node and target RAN node support distributed NAS signaling and are connected to or communicated with each other using servicebased architecture (SBA). In that sense, the source RAN node can send control signaling to the target RAN node, and vice versa. An Xn interface between the source RAN node and the target RAN node is no present in this scenario.

[0034] FIG. 3 is a flowchart of a method for performing handover 100 implemented by a source RAN node according to an embodiment of the present application. Referring to FIG. 3, the method 100 includes the following steps.

[0035] In Step 102, the source RAN node communicates a first handover (HO) required message with a source access and mobility management function (AMF) for the source AMF to select a target AMF. The source RAN node may directly communicate with the source AMF to send the first HO required message to the source AMF. The target AMF determines a target RAN node based on the first HO required message. More specifically, the first HO required message can include a target RAN node identifier (ID) which is transferred from the source AMF to the target AMF such that the target AMF can determine the target RAND node based on the target RAN node ID. In addition, the source AMF may select the target AMF based on the target RAN node ID as well.

[0036] In Step 104, the source RAN node directly communicates a second HO required message with a session management function (SMF), wherein the second HO required message includes all or part of protocol data unit (PDU) session-related information for PDU session handover. Instead of relying on the AMF to coordinate the handover procedure with the SMF, the sourceAtty. Dkt. No. 10085-01-0172-PCTRAN node directly communicates with the SMF with NAS signaling, for example, using the SB A. With the second HO required message, PDU session handover can be realized since all the PDU session-related information is transferred. The SMF may also need to perform required session modification procedure with a user plane function (UPF) to complete the PDU session handover.

[0037] In Step 106, the source RAN node receives a HO command message from the target RAN node to handover a user equipment (UE) to the target RAN node. The source RAN node may (directly) communicate with the target RAN node with NAS signaling using the SB A to (directly) receive the HO command message from the target RAN node via the SB A. Furthermore, the first HO required message may include an address of the source RAN node such that the target RAN node knows how to reach the source RAN node to (directly) send the HO command message to the source RAN node.’

[0038] With the method for performing handover 100, a handover procedure can be implemented in a communication system (e.g., 6G system) without relying on AMF as anchor. This can reduce latency and enhance communication performance.

[0039] FIG. 4 is a flowchart of a method for performing handover 200 implemented by a target RAN node according to an embodiment of the present application. Referring to FIG. 4, the method 200 includes the following steps.

[0040] In Step 202, the target RAN node communicates with a target access and mobility management function (AMF) to receive a first handover (HO) request message from the target AMF. The target RAN node may directly communicate with the target AMF to receive the first HO request message. The target AMF is selected by a source AMF. A source RAN node is determined by the target RAN node based on the first HO request message. More specifically, the source AMF may select the target AMF based on a target RAN node identifier (ID). The target RAN node ID may also be transferred from the source AMF to the target AMF for target AMF to determine the target RAND node. The first HO request message may include an address of the source RAN node such that the target RAN node knows how to reach the source RAN node by using the address of the source RAN node.

[0041] In Step 204, the target RAN node directly communicates with a session management function (SMF) to receive a second HO request message from the SMF, wherein the second HO request message includes all or part of protocol data unit (PDU) session-related information for PDU session handover. Instead of relying on the AMF to coordinate the handover procedure with the SMF, the target RAN node directly communicates with the SMF with NAS signaling, forAtty. Dkt. No. 10085-01-0172-PCT example, using the SBA. With the second HO request message, PDU session handover can be realized since all the PDU session-related information is transferred. The SMF may also need to perform required session modification procedure with a user plane function (UPF) to complete the PDU session handover.

[0042] In Step 206, the target RAN node sends a HO command message to the source RAN node to handover a user equipment (UE) to the target RAN node. The target RAN node may (directly) communicate with the source RAN node with NAS signaling using the SBA to (directly) send the HO command message to the source RAN node via the SBA. Furthermore, since the first HO request message may include the address of the source RAN node, the target RAN node can know how to reach the source RAN node to (directly) send the HO command message to the source RAN node.

[0043] With the method for performing handover 200, a handover procedure can be implemented in a communication system (e.g., 6G system) without relying on AMF as anchor. This can reduce latency and enhance communication performance.

[0044] FIG. 5 illustrates a call flow for performing handover according to an embodiment of the present application. Referring to FIG. 5, the handover procedure includes the following steps.

[0045] In Step 1, the source RAN node decides performs handover to a target RAN node for the UE. That is, the handover procedure will be started.

[0046] In Step 2, the source RAN node sends a first HO required message to the source AMF. In the first HO required message, a target RAN node identifier (ID), source RAN node ID and address, a source-to-target container are included. These information can be transferred from the source AMF to the target AMF via UE context transfer and further to the target RAN node to facilitate UE handover. Based on the source RAN node ID and address, it allows the target RAN node to directly send a HO command message to the source RAN node to realize the handover of the UE from the source RAN node to the target RAN node.

[0047] In Step 3, upon receiving the first HO required message, the source AMF selects the target AMF. Specifically, the source AMF selects the target AMF based on the target RAN node ID.

[0048] In Step 4, after selecting the target AMF, the source AMF sends the target RAN node ID, the source RAN node ID and address and the source-to-target container to the target AMF via UE context transfer.

[0049] In Step 5, the source RAN node sends a second HO required message to the SMF. The second HO required message includes all or part of PDU session-related information for PDUAtty. Dkt. No. 10085-01-0172-PCT session handover. With the second HO required message, PDU session handover can be realized since all or part of the PDU session-related information is transferred.

[0050] In Step 6, the SMF performs required session modification procedure with the UPF.

[0051] In Step 7, the target AMF sends a first HO request message to the target RAN node. The first HO request message includes the source RAN ID and address and the source-to-target container. At this point, the target RAN node knows how to reach the source RAN node vis SBA interface since it has the source RAN ID and address.

[0052] In Step 8, the SMF sends a second HO request message to the target RAN node. The second HO request message includes all or part of PDU session-related information for PDU session handover. With the second HO request message, PDU session handover can be realized since all or part of the PDU session-related information is transferred.

[0053] In Step 9, the target RAN node sends the HO command message directly to the source RAN node via SBA interface. The HO command message includes necessary information for performing UE handover.

[0054] In Step 10, the source RAN node instructs the UE to perform HO.

[0055] In Step 11, the UE synchronizes with the target RAN node, anchors at the target RAN node and sends a HO confirmation message to the target RAN node to complete handover.

[0056] In Step 12, the target RAN node sends a first HO notification to the target AMF to confirm HO completion.

[0057] In Step 13, the target RAN node sends a second HO notification to the target SMF to confirm HO completion.

[0058] In this application, the key proposals are listed as follows:

[0059] In the handover procedure, the RAN node will rely on the AMF to handle mobility management-related procedures and rely on the SMF to handle session management-related procedures.

[0060] In the handover message sent from the RAN node to the AMF, the following new information is included: the address of the source RAN node.

[0061] Once the target RAN node receives a request from the AMF and the SMF, it will directly communicate with the source RAN node, via the SBA interface, using the received address of the source RAN node, to realize the handover.

[0062] The source-to-target container can be transferred via AMF or can be directly transferred from the source RAN node to the target RAN node via the SBA interface.Atty. Dkt. No. 10085-01-0172-PCT

[0063] FIG. 6 is a block diagram of a source RAN node according to an embodiment of the present application. As shown in FIG. 6, the source RAN node 300 includes a first communication module 301, a second communication module 302, and a first receiving module 303. The first communication module is configured to communicate a first handover (HO) required message with a source access and mobility management function (AMF) for the source AMF to select a target AMF, which determines a target RAN node based on the first HO required message. The second communication module 302 is configured to directly communicate a second HO required message with a session management function (SMF), wherein the second HO required message includes all or part of protocol data unit (PDU) session-related information for PDU session handover. The first receiving module 303 is configured to receive a HO command message from the target RAN node to handover a user equipment (UE) to the target RAN node. This facilitates implementing a handover procedure in a communication system (e.g., 6G system) without relying on AMF as anchor, thereby reducing latency and enhancing communication performance. Other details of the source RAN node 300 may be referred to the method 100 described above and are not repeated herein.

[0064] FIG. 7 is a block diagram of a target RAN node according to an embodiment of the present application. As shown in FIG. 7, the target RAN node 400 includes a third communication module 401, a fourth communication module 402, and a sending module 403. The third communication module 401 is configured to communicate with a target access and mobility management function (AMF) to receive a first handover (HO) request message from the target AMF that is selected by a source AMF, wherein a source RAN node is determined by the target RAN node based on the first HO request message. The fourth communication module 402 is configured to directly communicate with a session management function (SMF) to receive a second HO request message from the SMF, wherein the second HO request message includes all or part of protocol data unit (PDU) session-related information for PDU session handover. The sending module 403 is configured to send a HO command message to the source RAN node to handover a user equipment (UE) to the target RAN node. This facilitates implementing a handover procedure in a communication system (e.g., 6G system) without relying on AMF as anchor, thereby reducing latency and enhancing communication performance. Other details of the target RAN node 400 may be referred to the method 200 described above and are not repeated herein.

[0065] The embodiment of the present application further provides a source radio access network (RAN) node, including at least one memory configured to store program instructions; and at leastAtty. Dkt. No. 10085-01-0172-PCT one processor configured to execute the program instructions, which cause the at least one processor to communicate a first handover (HO) required message with a source access and mobility management function (AMF) for the source AMF to select a target AMF, which determines a target RAN node based on the first HO required message, directly communicate a second HO required message with a session management function (SMF), wherein the second HO required message includes all or part of protocol data unit (PDU) session-related information for PDU session handover, and receive a HO command message from the target RAN node to handover a user equipment (UE) to the target RAN node. Other details of the source RAN node 300 may be referred to the method 100 described above and are not repeated herein.

[0066] The embodiment of the present application further provides a target radio access network (RAN) node, including at least one memory configured to store program instructions; and at least one processor configured to execute the program instructions, which cause the at least one processor to communicate with a target access and mobility management function (AMF) to receive a first handover (HO) request message from the target AMF that is selected by a source AMF, wherein a source RAN node is determined by the target RAN node based on the first HO request message, directly communicate with a session management function (SMF) to receive a second HO request message from the SMF, wherein the second HO request message includes all or part of protocol data unit (PDU) session-related information for PDU session handover, and send a HO command message to the source RAN node to handover a user equipment (UE) to the target RAN node. Other details of the target RAN node 400 may be referred to the method 200 described above and are not repeated herein.

[0067] The embodiment of the present application further provides a computer readable storage medium for storing a computer program. The computer readable storage medium enables a computer to execute corresponding processes implemented in each of the methods of the embodiments of the present application. For brevity, details will not be described herein again.

[0068] The embodiment of the present application further provides a computer program product including computer program instructions. The computer program product enables a computer to execute corresponding processes implemented in each of the methods of the embodiments of the present application. For brevity, details will not be described herein again.

[0069] The embodiment of the present application further provides a computer program. The computer program enables a computer to execute corresponding processes implemented in eachAtty. Dkt. No. 10085-01-0172-PCT of the methods of the embodiments of the present application. For brevity, details will not be described herein again.

[0070] The description of above device embodiments is similar to the description of above method embodiments, having beneficial effects similar to the method embodiments. For technical details not disclosed in the device embodiments of the present application, please refer to the description of the method embodiments of the present application for the purpose of understanding.

[0071] Those of skill in the art will appreciate that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0072] Further, those of skill in the art will appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

[0073] The methods, sequences and / or algorithms described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor.

[0074] It should be understood that any embodiments disclosed herein as being “non-transitory” do not exclude any physical storage medium, but rather exclude only the interpretation that the medium can be construed as a transitory propagating signal.Atty. Dkt. No. 10085-01-0172-PCT

[0075] The elements and components of an embodiment of the invention may be physically, functionally and logically implemented in any suitable way. Indeed, the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units. Although the present invention has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the present invention is limited only by the accompanying claims. Additionally, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognize that various features of the described embodiments may be combined in accordance with the invention. In the claims, the term ‘including’ does not exclude the presence of other elements or steps.

[0076] Furthermore, although individually listed, a plurality of means, elements or method steps may be implemented by, for example, a single unit or processor. Additionally, although individual features may be included in different claims, these may possibly be advantageously combined, and the inclusion in different claims does not imply that a combination of features is not feasible and / or advantageous. Also, the inclusion of a feature in one category of claims does not imply a limitation to this category, but rather indicates that the feature is equally applicable to other claim categories, as appropriate.

[0077] Furthermore, the order of features in the claims does not imply any specific order in which the features must be performed and in particular the order of individual steps in a method claim does not imply that the steps must be performed in this order. Rather, the steps may be performed in any suitable order. In addition, singular references do not exclude a plurality. Thus, references to ‘a’, ‘an’, ‘first’, ‘second’, etc. do not preclude a plurality.

[0078] Above all, while the preferred embodiments of the present application have been illustrated and described in detail, various modifications and alterations can be made by persons of ordinary skill in the art. The embodiment of the present application is therefore described in an illustrative but not restrictive sense. It is intended that the present application should not be limited to the particular forms as illustrated, and that all modifications and alterations which maintain the spirit and realm of the present application are within the scope as defined in the appended claims.

Claims

Atty. Dkt. No. 10085-01-0172-PCTWHAT IS CLAIMED IS:

1. A method for performing handover, performed by a source radio access network (RAN) node, comprising: communicating a first handover (HO) required message with a source access and mobility management function (AMF) for the source AMF to select a target AMF, which determines a target RAN node based on the first HO required message; directly communicating a second HO required message with a session management function (SMF), wherein the second HO required message includes all or part of protocol data unit (PDU) session-related information for PDU session handover; and receiving a HO command message from the target RAN node to handover a user equipment (UE) to the target RAN node.

2. The method of claim 1, wherein the HO command message is received from the target RAN node via service-based architecture (SBA).

3. The method of claim 1 or 2, wherein the first HO required message comprises a target RAN node identifier (ID) used for the target AMF to determine the target RAND node.

4. The method of any of claims 1 to 3, wherein the first HO required message comprises an address of the source RAN node that is used by the target RAN node to send the HO command message to the source RAN node.

5. The method of any of claims 1 to 4, wherein UE context is transferred from the source AMF to the target AMF.

6. A method for performing handover, performed by a target radio access network (RAN) node, comprising: communicating with a target access and mobility management function (AMF) to receive a first handover (HO) request message from the target AMF that is selected by a source AMF, wherein a source RAN node is determined by the target RAN node based on the first HO request message; directly communicating with a session management function (SMF) to receive a second HO request message from the SMF, wherein the second HO request message includes all or part of protocol data unit (PDU) session-related information for PDU session handover; and sending a HO command message to the source RAN node to handover a user equipment (UE) to the target RAN node.Atty. Dkt. No. 10085-01-0172-PCT7. The method of claim 6, wherein the HO command message is sent to the source RAN node via service-based architecture (SB A).

8. The method of claim 6 or 7, wherein the first HO request message comprises an address of the source RAN node that is used by the target RAN node to send the HO command message to the source RAN node.

9. The method of any of claims 6 to 8, wherein UE context is transferred from the source AMF to the target AMF.

10. The method of any of claims 6 to 9, further comprising: receiving a HO confirmation message from the UE to complete handover.

11. The method of any of claims 6 to 10, further comprising: sending a first HO notification to the target AMF to confirm HO completion.

12. The method of any of claims 6 to 11, further comprising: sending a second HO notification to the target SMF to confirm HO completion.

13. A source radio access network (RAN) node, comprising: at least one memory configured to store program instructions; and at least one processor configured to execute the program instructions, which cause the at least one processor to execute the method of any of claims 1 to 5.

14. A target radio access network (RAN) node, comprising: at least one memory configured to store program instructions; and at least one processor configured to execute the program instructions, which cause the at least one processor to execute the method of any of claims 6 to 12.

15. A source radio access network (RAN) node, comprising: a first communication module, configured to communicate a first handover (HO) required message with a source access and mobility management function (AMF) for the source AMF to select a target AMF, which determines a target RAN node based on the first HO required message; a second communication module, configured to directly communicate a second HO required message with a session management function (SMF), wherein the second HO required message includes all or part of protocol data unit (PDU) session-related information for PDU session handover; and a first receiving module, configured to receive a HO command message from the target RAN node to handover a user equipment (UE) to the target RAN node.Atty. Dkt. No. 10085-01-0172-PCT16. The source RAN node of claim 15, wherein the HO command message is received from the target RAN node via service-based architecture (SBA).

17. The source RAN node of claim 15 or 16, wherein the first HO required message comprises a target RAN node identifier (ID) used for the target AMF to determine the target RAND node.

18. The source RAN node of any of claims 15 to 17, wherein the first HO required message comprises an address of the source RAN node that is used by the target RAN node to send the HO command message to the source RAN node.

19. The source RAN node of any of claims 15 to 18, wherein UE context is transferred from the source AMF to the target AMF.

20. A target radio access network (RAN) node, comprising: a third communication module, configured to communicate with a target access and mobility management function (AMF) to receive a first handover (HO) request message from the target AMF that is selected by a source AMF, wherein a source RAN node is determined by the target RAN node based on the first HO request message; a fourth communication module, configured to directly communicate with a session management function (SMF) to receive a second HO request message from the SMF, wherein the second HO request message includes all or part of protocol data unit (PDU) session-related information for PDU session handover; and a sending module, configured to send a HO command message to the source RAN node to handover a user equipment (UE) to the target RAN node.

21. The target RAN node of claim 20, wherein the HO command message is sent to the source RAN node via service-based architecture (SBA).

22. The target RAN node of claim 20 or 21, wherein the first HO request message comprises an address of the source RAN node that is used by the target RAN node to send the HO command message to the source RAN node.

23. The target RAN node of any of claims 20 to 22, wherein UE context is transferred from the source AMF to the target AMF.

24. The target RAN node of any of claims 20 to 23, further comprising: a second receiving module, configured to receive a HO confirmation message from the UE to complete handover.

25. The target RAN node of any of claims 20 to 24, wherein the sending module is further configured to send a first HO notification to the target AMF to confirm HO completion.Atty. Dkt. No. 10085-01-0172-PCT26. The target RAN node of any of claims 20 to 25, wherein the sending module is further configured to send a second HO notification to the target SMF to confirm HO completion.

27. A non-transitory machine-readable storage medium having stored thereon instructions that, when executed by a computer, cause the computer to perform the method of any one of claims 1 to 5 or the method of any one of claims 6 to 12.

28. A chip, comprising: a processor, configured to call and run a computer program stored in a memory, to cause a device in which the chip is installed to execute the method of any one of claims 1 to 5 or the method of any one of claims 6 to 12.

29. A computer readable storage medium, in which a computer program is stored, wherein the computer program causes a computer to execute the method of any one of claims 1 to 5 or the method of any one of claims 6 to 12.

30. A computer program product, comprising a computer program, wherein the computer program causes a computer to execute the method of any one of claims 1 to 5 or the method of any one of claims 6 to 12.

31. A computer program, wherein the computer program causes a computer to execute the method of any one of claims 1 to 5 or the method of any one of claims 6 to 12.

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