Enhancements on sharing updated information with handover candidate radio access network nodes

Abstract

A method is provided that includes configuring a handover of a user equipment (UE) in which a handover request message is sent to candidate access nodes to prepare for the handover. The handover request message includes one or more parameters of one or more access node – core network interfaces related to the UE. The method includes receiving a UE-related request message from an access and mobility management function (AMF) that includes an update to at least one of the one or more parameters. And the method includes forwarding the update to the at least one of the one or more parameters to at least one of the candidate access nodes for use by a target access node of the at least one of the candidate access nodes in connection with the handover.

Description

ENHANCEMENTS ON SHARING UPDATED INFORMATION WITH HANDOVER CANDIDATESTECHNOLOGICAL FIELD

[0001] The present disclosure relates generally to telecommunications and, in particular, to handover of a user equipment in a telecommunications system.BACKGROUND

[0002] A telecommunications system can be seen as a facility that enables communication sessions between two or more entities such as user terminals, base stations and / or other nodes by providing carriers between the various entities involved in the communications path. A telecommunications system can be provided for example by means of a communication network and one or more compatible communication devices. The communication sessions may include, for example, communication of data for carrying communications such as voice, video, electronic mail (email), text message, multimedia and / or content data and so on. Non-limiting examples of services provided include two-way or multi-way calls, data communication or multimedia services and access to a data network system, such as the Internet.

[0003] In a wireless telecommunications system at least a part of a communication session between at least two stations occurs over a wireless link. Examples of wireless systems include public land mobile networks (PLMN), satellite based communication systems and different wireless local networks, for example wireless local area networks (WLAN). Some wireless systems can be divided into cells, and are therefore often referred to as cellular systems.

[0004] A user can access the telecommunications system by means of an appropriate communication device or terminal. A communication device of a user may be referred to as user equipment (UE) or user device. A communication device is provided with an appropriate signal receiving and transmitting apparatus for enabling communications, for example enabling access to a communication network or communications directly withother users. The communication device may access a carrier provided by a station, for example a base station of a cell, and transmit and / or receive communications on the carrier.

[0005] The telecommunications system and associated devices typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. Communication protocols and / or parameters which shall be used for the connection are also typically defined. One example of a telecommunications system is the Universal Mobile Telecommunications System (UMTS). Other examples of telecommunications systems are Long-Term Evolution (LTE), LTE Advanced and the so-called 5G or New Radio (NR) networks. NR is being standardized by the 3rd Generation Partnership Project (3 GPP).BRIEF SUMMARY

[0006] Example implementations of the present disclosure are directed to telecommunications and, in particular, to handover (e.g., conditional handover, lowerlayered triggered mobility) of a user equipment in a telecommunications system. The present disclosure includes, without limitation, the following example implementations.

[0007] Some example implementations provide an apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: configure a handover of a user equipment (UE) in which a handover request message is sent to candidate access nodes to prepare for the handover, the handover request message including one or more parameters of one or more of an access node - access and mobility management function (AMF) interface, or an access node - user plane function (UPF) interface, related to the UE; receive a UE -related request message from an AMF that includes an update to at least one of the one or more parameters of the at least one of the access node - AMF interface or the access node - UPF interface; and forward the update to the at least one of the one or more parameters to at least one of the candidate access nodes for use by a target access node of the at least one of the candidate access nodes in connection with the handover.

[0008] Some example implementations provide an apparatus comprising: means for configuring a handover of an user equipment (UE) in which a handover request message is sent to candidate access nodes to prepare for the handover, the handover request message including one or more parameters of one or more of an access node - access and mobility management function (AMF) interface, or an access node - user plane function (UPF) interface, related to the UE; means for receiving a UE-related request message from an AMF that includes an update to at least one of the one or more parameters of the at least one of the access node - AMF interface or the access node - UPF interface; and means for forwarding the update to the at least one of the one or more parameters to at least one of the candidate access nodes for use by a target access node of the at least one of the candidate access nodes in connection with the handover.

[0009] Some example implementations provide a method comprising: configuring a handover of a user equipment (UE) in which a handover request message is sent to candidate access nodes to prepare for the handover, the handover request message including one or more parameters of one or more of an access node - access and mobility management function (AMF) interface, or an access node - user plane function (UPF) interface, related to the UE; receiving a UE-related request message from an AMF that includes an update to at least one of the one or more parameters of the at least one of the access node - AMF interface or the access node - UPF interface; and forwarding the update to the at least one of the one or more parameters to at least one of the candidate access nodes for use by a target access node of the at least one of the candidate access nodes in connection with the handover.

[0010] Some example implementations provide a computer-readable storage medium that is non-transitory and has instructions stored therein that, in response to execution by at least one processing circuitry, causes an apparatus to at least: configure a handover of a user equipment (UE) in which a handover request message is sent to candidate access nodes to prepare for the handover, the handover request message including one or more parameters of one or more of an access node - access and mobility management function (AMF) interface, or an access node - user plane function (UPF) interface, related to the UE; receive a UE-related request message from an AMF that includes an update to at least one of the one or more parameters of the at least one of the access node - AMFinterface or the access node - UPF interface; and forward the update to the at least one of the one or more parameters to at least one of the candidate access nodes for use by a target access node of the at least one of the candidate access nodes in connection with the handover.

[0011] Some example implementations provide an apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: configure a handover of a user equipment (UE) in which a handover request message is sent to candidate access nodes to prepare the candidate access nodes for the handover, the handover request message including one or more parameters of an access node - access and mobility management function (AMF) interface related to the UE; receive a UE-related request message from an AMF that includes an update to at least one of the one or more parameters of the access node - AMF interface related to the UE; and send a message to the AMF that indicates the handover of the UE is configured to enable the AMF to avoid the update to the at least one of the one or more parameters while the handover is configured.

[0012] Some example implementations provide an apparatus comprising: means for configuring a handover of an user equipment (UE) in which a handover request message is sent to candidate access nodes to prepare the candidate access nodes for the handover, the handover request message including one or more parameters of an access node - access and mobility management function (AMF) interface related to the UE; means for receiving a UE-related request message from an AMF that includes an update to at least one of the one or more parameters of the access node - AMF interface related to the UE; and means for sending a message to the AMF that indicates the handover of the UE is configured to enable the AMF to avoid the update to the at least one of the one or more parameters while the handover is configured.

[0013] Some example implementations provide a method comprising: configuring a handover of a user equipment (UE) in which a handover request message is sent to candidate access nodes to prepare the candidate access nodes for the handover, the handover request message including one or more parameters of an access node - access and mobility management function (AMF) interface related to the UE; receiving a UE-related request message from an AMF that includes an update to at least one of the one or more parameters of the access node - AMF interface related to the UE; and sending a message to the AMF that indicates the handover of the UE is configured to enable the AMF to avoid the update to the at least one of the one or more parameters while the handover is configured.

[0014] Some example implementations provide a computer-readable storage medium that is non-transitory and has instructions stored therein that, in response to execution by at least one processing circuitry, causes an apparatus to at least: configure a handover of a user equipment (UE) in which a handover request message is sent to candidate access nodes to prepare the candidate access nodes for the handover, the handover request message including one or more parameters of an access node - access and mobility management function (AMF) interface related to the UE; receive a UE-related request message from an AMF that includes an update to at least one of the one or more parameters of the access node - AMF interface related to the UE; and send a message to the AMF that indicates the handover of the UE is configured to enable the AMF to avoid the update to the at least one of the one or more parameters while the handover is configured.

[0015] Some example implementations provide an apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: receive a handover request message from a source access node during preparation of candidate access nodes for a handover of a user equipment (UE), the handover request message including user plane transport layer information for an access node - user plane function (UPF) interface related to the UE; carry out the handover of the UE; carry out a path switch procedure with an access and mobility function (AMF), in connection with the handover, and during which an update to the user plane transport layer information is received from the AMF; and forward the update to the user plane transport layer information to one or more of the candidate access nodes for use by a target access node of the one or more candidate access nodes in connection with a subsequent handover.

[0016] Some example implementations provide an apparatus comprising: means for receiving a handover request message from a source access node during preparation of candidate access nodes for a handover of an user equipment (UE), the handover request message including user plane transport layer information for an access node - user plane function (UPF) interface related to the UE; means for carrying out the handover of the UE; means for carrying out a path switch procedure with an access and mobility function (AMF), in connection with the handover, and during which an update to the user plane transport layer information is received from the AMF; and means for forwarding the update to the user plane transport layer information to one or more of the candidate access nodes for use by a target access node of the one or more candidate access nodes in connection with a subsequent handover.

[0017] Some example implementations provide a method comprising: receiving a handover request message from a source access node during preparation of candidate access nodes for a handover of a user equipment (UE), the handover request message including user plane transport layer information for an access node - user plane function (UPF) interface related to the UE; carrying out the handover of the UE; carrying out a path switch procedure with an access and mobility function (AMF), in connection with the handover, and during which an update to the user plane transport layer information is received from the AMF; and forwarding the update to the user plane transport layer information to one or more of the candidate access nodes for use by a target access node of the one or more candidate access nodes in connection with a subsequent handover.

[0018] Some example implementations provide a computer-readable storage medium that is non-transitory and has instructions stored therein that, in response to execution by at least one processing circuitry, causes an apparatus to at least: receive a handover request message from a source access node during preparation of candidate access nodes for a handover of a user equipment (UE), the handover request message including user plane transport layer information for an access node - user plane function (UPF) interface related to the UE; carry out the handover of the UE; carry out a path switch procedure with an access and mobility function (AMF), in connection with the handover, and during which an update to the user plane transport layer information is received from the AMF; and forward the update to the user plane transport layer information to one or more of thecandidate access nodes for use by a target access node of the one or more candidate access nodes in connection with a subsequent handover.

[0019] These and other features, aspects, and advantages of the present disclosure will be apparent from a reading of the following detailed description together with the accompanying figures, which are briefly described below. The present disclosure includes any combination of two, three, four or more features or elements set forth in this disclosure, regardless of whether such features or elements are expressly combined or otherwise recited in a specific example implementation described herein. This disclosure is intended to be read holistically such that any separable features or elements of the disclosure, in any of its aspects and example implementations, should be viewed as combinable unless the context of the disclosure clearly dictates otherwise.

[0020] It will therefore be appreciated that this Brief Summary is provided merely for purposes of summarizing some example implementations so as to provide a basic understanding of some aspects of the disclosure. Accordingly, it will be appreciated that the above described example implementations are merely examples and should not be construed to narrow the scope or spirit of the disclosure in any way. Other example implementations, aspects and advantages will become apparent from the following detailed description taken in conjunction with the accompanying figures which illustrate, by way of example, the principles of some described example implementations.BRIEF DESCRIPTION OF THE FIGURE(S)

[0021] Having thus described example implementations of the disclosure in general terms, reference will now be made to the accompanying figures, which are not necessarily drawn to scale, and wherein:

[0022] FIG. 1 illustrates a telecommunications system that includes one or more public land mobile networks (PLMNs) coupled to one or more external data networks, according to some example implementations of the present disclosure;

[0023] FIG. 2 illustrates a deployment of a PLMN, according to some example implementations;

[0024] FIG. 3 more particularly depicts aspects of a 5G deployment, referred to at times as the 5G system (5GS), according to some example implementations;

[0025] FIGS. 4 A and 4B illustrate a signaling chart of a conditional handover (CHO) procedure for a user equipment (UE);

[0026] FIG. 5 illustrates a signaling chart for a lower-layer triggered mobility (LTM) procedure;

[0027] FIGS. 6 A, 6B and 6C illustrate a signaling chart for a conventional LTM procedure in which an identity (ID) allocated to a UE by an access and mobility function (AMF) is updated;

[0028] FIGS. 7 A and 7B illustrate a signaling chart for a conventional LTM procedure in which one or more user plane function (UPF) endpoints of one or more user plane transport bearers are updated or added;

[0029] FIGS. 8 A and 8B illustrate a signaling chart for a LTM procedure in which the ID allocated to the UE by the AMF is updated, according to some example implementations;

[0030] FIGS. 9 A and 9B illustrate a signaling chart for a LTM procedure in which the ID allocated to the UE by the AMF is updated, according to other example implementations;

[0031] FIGS. 10A and 10B illustrate a signaling chart for a LTM procedure in which user plane transport layer information for a packet data unit (PDU) session is updated, according to some example implementations;

[0032] FIGS. 11 A and 11B illustrate a signaling chart for a LTM procedure in which user plane transport layer information for a PDU session is updated, according to other example implementations;

[0033] FIGS. 12A and 12B illustrate a signaling chart of CHO procedure in which the ID allocated to the UE by the AMF is updated, according to some example implementations;

[0034] FIG. 13 illustrates a signaling chart of CHO procedure in which user plane transport layer information for a PDU session is updated, according to some example implementations;

[0035] FIGS. 14A and 14B are flowcharts illustrating various steps in a method performed by a source access node, according to various example implementations;

[0036] FIG. 15 is a flowchart illustrating various steps in a method performed by a source access node, according to various other example implementations;

[0037] FIGS. 16A and 16B are flowcharts illustrating various steps in a method performed by a target access node, according to various example implementations; and

[0038] FIG. 17 illustrates an apparatus according to some example implementations.DETAILED DESCRIPTION

[0039] Some implementations of the present disclosure will now be described more fully hereinafter with reference to the accompanying figures, in which some, but not all implementations of the disclosure are shown. Indeed, various implementations of the disclosure may be embodied in many different forms and should not be construed as limited to the implementations set forth herein; rather, these example implementations are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Like reference numerals refer to like elements throughout.

[0040] Unless specified otherwise or clear from context, references to first, second or the like should not be construed to imply a particular order. A feature described as being above another feature (unless specified otherwise or clear from context) may instead be below, and vice versa; and similarly, features described as being to the left of another feature else may instead be to the right, and vice versa. Also, while reference may be made herein to quantitative measures, values, geometric relationships or the like, unless otherwise stated, any one or more if not all of these may be absolute or approximate to account for acceptable variations that may occur, such as those due to engineering tolerances or the like.

[0041] As used herein, unless specified otherwise or clear from context, the “or” of a set of operands is the “inclusive or” and thereby true if and only if one or more of the operands is true, as opposed to the “exclusive or” which is false when all of the operands are true. Thus, for example, “[A] or [B]” is true if [A] is true, or if [B] is true, or if both [A] and [B] are true. Further, the articles “a” and “an” mean “one or more,” unless specified otherwise or clear from context to be directed to a singular form. Furthermore, it should be understood that unless otherwise specified, the terms “data,” “content,”“digital content,” “information,” and similar terms may be at times used interchangeably. The term “network” may refer to a group of interconnected computers including clients and servers; and within a network, these computers may be interconnected directly or indirectly by various means including via one or more switches, routers, gateways, access points or the like.

[0042] Reference may be made herein to terms specific to a particular system, architecture or the like, but it should be understood that example implementations of the present disclosure may be equally applicable to any of a number of systems, architectures and the like. For example, reference may be made to 3 GPP technologies such as Global System for Mobile Communications (GSM), UMTS, LTE, LTE Advanced, 5GNR, 5G Advanced and 6G; however, it should be understood that example implementations of the present disclosure may be equally applicable to non-3GPP technologies such as IEEE 802, Bluetooth and Bluetooth Low Energy.

[0043] Further, as used in this application, the term “circuitry” may refer to one or more or all of the following: (a) hardware-only circuit implementations (such as implementations in only analog and / or digital circuitry); (b) combinations of hardware circuits and software, such as (as applicable): (i) a combination of analog and / or digital hardware circuit(s) with software / firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions); or (c) hardware circuit(s) and / or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

[0044] The above definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0045] FIG. 1 illustrates a telecommunications system 100 according to various example implementations of the present disclosure. The telecommunications system generally includes one or more telecommunications networks. As shown, for example, the system includes one or more public land mobile networks (PLMNs) 102 coupled to one or more other external data networks 104 - notably including a wide area network (WAN) such as the Internet. Each of the PLMNs includes a core network(CN) 106 backbone such as the Evolved Packet Core (EPC) of LTE, the 5G core network (5GC) or the like; and each of the core networks and the Internet are coupled to one or more radio access networks (RANs) 108, air interfaces or the like that implement one or more radio access technologies (RATs). As used herein, a “network device” refers to any suitable device at a network side of a telecommunications network. Examples of suitable network devices are described in greater detail below.

[0046] In addition, the system includes one or more radio units that may be varyingly known as user equipment (UE) 110, terminal device, terminal equipment, mobile station or the like. The UE is generally a device configured to communicate with a network device or a further UE in a telecommunications network. The UE may be a portable computer (e.g., laptop, notebook, tablet computer), mobile phone (e.g., cell phone, smartphone), wearable computer (e.g., smartwatch), or the like. In other examples, the UE may be an Internet of things (loT) device, an industrial loT (IIoT device), a vehicle equipped with a vehicle-to-everything (V2X) communication technology, or the like. In some examples, as referenced by 3GPP, the UE may be a narrowband loT (NB-IoT) device, an enhanced machine-type communication (eMTC) device, a reduced capability (RedCap) device, an ambient loT device, or the like.

[0047] In operation, these UEs 110 may be configured to connect to one or more of the RANs 108 according to their particular radio access technologies to thereby access a particular CN 106 of a PLMN 102, or to access one or more of the external data networks 104 (e.g., the Internet). The external data network may be configured to provide Internet access, operator services, 3rd party services, etc. For example, the International Telecommunication Union (ITU) has classified 5G mobile network services into three categories: enhanced mobile broadband (eMBB), ultra-reliable and low-latencycommunications (URLLC), and massive machine type communications (mMTC) or massive internet of things (MIoT).

[0048] Examples of radio access technologies include 3 GPP radio access technologies such as GSM, UMTS, LTE, LTE Advanced, 5G NR, 5G Advanced, and 6G. Other examples of radio access technologies include IEEE 802 technologies such as IEEE 802.11 (Wi-Fi), IEEE 802.15 (e.g., 802.15.1 (WPAN / Bluetooth), 802.15.4 (Zigbee) and 802.15.6 (WBAN)), Bluetooth, Bluetooth Low Energy (BLE), ultra wideband (UWB), and the like. Generally, a radio access technology may refer to any 2G, 3G, 4G, 5G, 6G or higher generation mobile communication technology and their different versions, as well as to any other wireless radio access technology that may be arranged to interwork with such a mobile communication technology to provide access to the CN 106 of a mobile network operator (MNO).

[0049] In various examples, a RAN 108 may be configured as one or more macrocells, microcells, picocells, femtocells or the like. The RAN may generally include one or more radio access nodes (at times more simply referred to as “access nodes” or “nodes”) that are configured to provide cells to interact with UEs 110. In various examples, a radio access node may be referred to as a base station (BS), access point (AP), base transceiver station (BTS), Node B (NB), evolved NB (eNB), macro BS, NB (MNB) or eNB (MeNB), home BS, NB (HNB) or eNB (HeNB), next generation NB (gNB), enhanced gNB (en-gNB), next generation eNB (ng-eNB), or the like. The RAN may include some type of network controlling / goveming entity responsible for control of the radio access nodes. The network controlling / goveming entity and radio access node may be separate or integrated into a single apparatus. The network controlling / goveming entity may include processing circuity configured to carry out various management functions, etc. The processing circuity may be associated with a memory, computer- readable storage medium or database for maintaining information required in the management functions.

[0050] ARAN 108 may be centralized or distributed. In various examples, components of a RAN may be interconnected by Ethernet, Gigabit Ethernet, Asynchronous Transfer Mode (ATM), optical fiber, dark fiber, passive wavelength division multiplexing (WDM), WDM passive optical network (WDM-PON), opticaltransport network (OTN), time sensitive networking (TSN) and / or any other data link layer network, possibly including radio links. The RAN may be connected to a CN 106 through one or more gateways, network functions or the like.

[0051] As will be appreciated, a PLMN 102 may be deployed in a number of different manners. FIG. 2 illustrates a deployment 200 of a PLMN, such as a 4G LTE, 5G or 6G deployment, according to some example implementations. As shown, the deployment includes a CN 106, and RAN 108 with one or more radio access nodes 202 configured to interact with UEs 110. In a 4G LTE deployment, the EPC is the CN, and the evolved UMTS terrestrial radio access network (E-UTRAN) is the RAN; and the E- UTRAN includes one or more eNBs (radio access nodes) configured to connect UEs to the E-UTRAN to thereby access the EPC. Similarly, in a 5G deployment, the 5GC is the CN 106, and the next generation (NG) radio access network (NG-RAN) is the RAN 108; and the NG-RAN includes one or more gNBs (radio access nodes) configured to connect UEs 110 to the NG-RAN to thereby access the 5GC. The term ‘gNB’ in 5G may correspond to the eNB in 4G LTE.

[0052] Some deployments of 4G LTE and 5G in particular are considered standalone (SA) deployments. Other deployments combine 4G LTE and 5G technologies, and are referred to as non- standalone (NSA) deployments. In some deployments, the E-UTRAN includes one or more ng-eNBs that are configured to communicate with the 5GC, and that may also be configured to communicate with one or more gNBs. Similarly, in another deployment, the NG-RAN may include one or more en-gNBs that are configured to communicate with the EPC, and that may also be configured to communicate with one or more eNBs. In various instances, a single UE 110, a dual-mode or multimode UE, may support multiple (two or more) RANs — thereby being configured to connect to multiple RANs, such as 4G LTE and 5G.

[0053] FIG. 3 more particularly depicts aspects of a 5G deployment for a MNO, referred to at times as the 5G system (5GS) 300, according to some example implementations. As shown, the 5G deployment includes a 5GC 302, and NG-RAN 304 with one or more gNBs 306 configured to connect UEs 110 to the NG-RAN to thereby access the 5GC. The 5GC may include a number of network functions (NFs) divided between the control plane (CP) and the user plane (UP). In particular, the 5GC mayinclude, for example, an access and mobility management function (AMF) 308, a session management function (SMF) 310, a user plane function (UPF) 312, and the like. Another example of a NF is a policy control function (PCF).

[0054] In the control plane, the AMF 308 is configured to provide UE-based authentication, authorization, mobility management, etc. The SMF 310 is configured to provide various functionality including session management (SM), UE Internet Protocol (IP) address allocation and management, selection and control of UPF (s) 312, control part of policy enforcement and quality of service (QoS), lawful intercept, termination of SM parts of NAS messages, downlink data notification (DDN), roaming functionality, handle local enforcement to apply QoS for service level agreements (SLAs), charging data collection and charging interface, etc. If the UE 110 has multiple sessions, different SMFs may be allocated to each session to manage them individually and possibly provide different functionalities per session.

[0055] The UPF 312 supports various user plane operations and functionalities, such as packet routing and forwarding, traffic handling (e.g., QoS enforcement), an anchor point for intra-RAT / inter-RAT mobility (when applicable), packet inspection and policy rule enforcement, lawful intercept (UP collection), traffic accounting and reporting, etc. The UPF is the point of interconnect between the 5GC and external data networks (i.e., point of ingress or egress for a data network), and routes packets to and from the data network. As explained above, data network may be configured to provide Internet access, operator services, 3rd party services, etc.

[0056] As also shown in FIG. 3, in some deployments, operations of the gNB 306 or other radio access node may be carried out, at least partly, in a central / centralized unit (CU) 314 (referred to at times as a gNB-CU), such as a server, host or node, operationally coupled to a distributed unit (DU) 316 (referred to at times as a gNB-DU), such as a radio head / node. It is also possible that node operations may be distributed among a plurality of servers, hosts or nodes.

[0057] It should also be understood that the distribution of work between 5GC 302 operations and gNB 306 operations may vary depending on implementation. Thus, a 5G network architecture may be based on a so-called CU-DU split. One CU 314 / gNB-CU (central node) may control one or more DUs 316 / gNB-DUs. The gNB-CU may controla plurality of spatially separated gNB-DUs, acting at least as transmit / receive (Tx / Rx) nodes. In some example implementations, however, the gNB-DUs (also called DU) may include, for example, a radio link control (RLC), medium access control (MAC) layer and a physical (PHY) layer, whereas the gNB-CU (also called a CU) may include the layers above the RLC layer, such as a packet data convergence protocol (PDCP) layer, a radio resource control (RRC), and an internet protocol (IP) layer. Other functional splits are also possible. It is considered that a skilled person is familiar with the open systems interconnection (OSI) model and the functionalities within each layer.

[0058] In some example implementations, the server or CU 314 may generate a virtual network through which the server communicates with the radio node. In general, virtual networking may involve a process of combining hardware and software network resources and network functionality into a single, software-based administrative entity, a virtual network. Such virtual network may provide flexible distribution of operations between the server and the radio head / node. In practice, any digital signal processing task may be performed in either the CU or the DU 316, and the boundary where the responsibility is shifted between the CU and the DU may be selected according to implementation.

[0059] Although only one radio access node 202 is shown in FIG. 2, the deployment may include multiple radio access nodes, and at least some of the radio access nodes may be connected to one another by a network interface, such as an Xn interface. Similarly, the radio access nodes may be connected to the CN 106 by a network interface. In 5G NR, the network interface between a gNB 306 and the 5GC 302 is referred to as the NG interface. The NG interface is divided into the NG control plane interface (NG-C), which is a network interface between the gNB and AMF 308, and the NG user plane interface (NG-U), which is the interface between the gNB and the UPF 312. These and other network interfaces may support the exchange of signaling messages between network entities. The signaling messages may be formatted according to an application layer protocol. Examples of application protocols include the NG application protocol (NGAP) for the NG-C interface between the gNB and AMF, and the Xn application protocol (XnAP) for the Xn interface between gNBs.

[0060] For a UE 110 in an RRC connected state, it is generally desirable to keep the UE’s traffic uninterrupted when the UE moves within a cell (at times referred to as a radio cell) or across different cells of one or more radio access nodes 202 (e.g., gNBs 306). To continuously monitor the UE’s radio link condition toward a serving cell provided by a serving radio access node, the UE may be configured to measure received signal level and quality from the serving cell as well as a list of configured neighboring cells, and report the results to the radio access node periodically and / or whenever a configured reporting event is met. These measurements may then be evaluated at the radio access node, and may result in preparation of one target cell (conventional handover) or multiple candidate (candidate target) cells (conditional handover), and a conventional / conditional handover of the UE from the serving cell provided by the serving radio access node (a “source access node” or more simply a “source node”) to a new cell provided by a target radio access node (a “target access node” or more simply a “target node”).

[0061] In the case of conditional handover (CHO), a UE 110 may be configured with a CHO command containing the candidate cell configuration and one or more CHO conditions for carrying out the handover (HO) to one or more candidate cells. The condition may be based on radio measurements. For example, a condition may be that a measured reference signal received power (RSRP) from the serving cell falls below a threshold RSRP. Each of the candidate cell(s) may have prepared a necessary configuration, such as contention free random access (CFRA) resources for the UE. Such configuration may then be communicated to the UE in the CHO command. When UE evaluates the CHO condition and determines that the condition holds for a specific candidate cell, UE may be configured to apply the CHO command and use the reserved CFRA resources to initiate the random access procedure to the candidate cell. In some examples, the UE may be configured with multiple conditions for multiple candidate cells.

[0062] The CHO procedure may be seen to be so designed that the UE 110 may perform / execute the handover without the need of the serving cell to trigger the HO execution after a measurement report from the UE.

[0063] FIGS. 4 A and 4B illustrate a signaling chart 400 of a CHO procedure involving a UE 110, a source gNB 306A that is currently serving (connected to) the UE, and one or more candidate gNBs 306B a target gNB and other potential target gNB(s) shown). Similar to the conventional HO procedure, as shown in FIG. 4A, the UE at step 401 may be configured to report measurements of one or more neighboring cells, and at step 402 send (transmit) a measurement report indicating relevant measurements for one or more candidate cells provided by the candidate gNB(s).

[0064] The source gNB 306A may at step 403 decide to initiate the handover procedure as a conditional handover procedure; and similar to the conventional HO procedure, initiate a handover preparation in which the source gNB at step 404 sends (transmits) a handover request message with a current configuration of the UE 110 towards each of the candidate gNB(s) 306B.

[0065] Each candidate gNB 306B may at step 405 perform admission control, such as to accept or reject the handover request, and at step 406 provide a handover request acknowledgement (ACK) message including a configuration of initial access resources for the UE 110. This configuration may be the same as or similar to the conventional HO procedure, including for example, a cell radio network temporary identifier (C-RNTI), a CFRA preamble, a DRB configuration, QoS flow to DRB mapping, UE capability related features enabled by the candidate gNB, or the like.

[0066] The source gNB 306A may then at step 407 send (transmit) a CHO command message that includes the configuration for the candidate cell towards the UE. The CHO command message may be sent by an RRC reconfiguration. The CHO command message also includes one or more CHO conditions for one or more candidate cells of the candidate gNB(s) 306B.

[0067] Upon receipt of the CHO command from the source gNB 306A, when the CHO command message is sent by an RRC reconfiguration, the UE 110 may at step 408 send (transmit) an RRC reconfiguration complete message to the source gNB. The UE maintains its connection with the source gNB, and at step 409 starts evaluating the CHO condition(s) for the candidate cell(s). If at least one candidate cell satisfies a corresponding CHO condition, as shown in FIG. 4B at step 410, the UE may at steps 411, 412, 413 obtain downlink (DL) and uplink (UL) synchronization and physical randomaccess channel (PRACH) access with the target candidate gNB 306B that provides the candidate cell.

[0068] The target gNB 306B at step 414 sends a handover success message to the source gNB 306A to inform that the UE 110 has successfully accessed the target cell. In return, the source gNB may at step 415 stop transmission / reception of user data to / from the UE, start forwarding user data to the target gNB 306B. The source gNB may at step 416 send a serving node (SN) status transfer message to the target gNB 306B. Also, the source gNB may at step 417 send a handover cancel message toward the other signaling connections or other candidate gNBs, if any, to cancel CHO for the UE. The target gNB and 5GC 302 may at step 418 carry out a path switch to switch the DL data path towards the target gNB and establish an interface instance towards the target gNB.

[0069] As the wireless generations evolve, so does the need for new and different solutions enabling more flexible, more efficient and sometimes faster procedures making the system seem more agile. One such enhancement includes moving the execution of the ‘handover’ from one cell to another from higher layers (L3), such as RRC, to lower layers. These lower layers may be either PHY (or layer 1, LI) or MAC (or layer 2, L2). This feature is currently referred to as Ll / L2-triggered mobility, or lower-layer triggered mobility (LTM), which may reduce latency, overhead and interruption time when compared to L3 handover based mobility. In a CU-DU split architecture, LTM may support one or more of intra-DU mobility, intra-CU inter-DU mobility, or inter-CU inter- DU mobility.

[0070] FIG. 5 illustrates a signaling chart 500 for an LTM procedure of a UE 110 in an RRC connected state with a gNB 306. During LTM preparation, as shown at step 501, the UE sends a L3 measurement report to the gNB, which decides to use LTM and initiate LTM candidate preparation. The gNB at step 502 transmits an RRC reconfiguration message to the UE, including the RRC configuration of one or more LTM candidate cells. The RRC configuration of an LTM candidate cell may be provided by an LTM candidate configuration information element (IE) within an LTM candidate IE. The RRC reconfiguration message may also include a configuration of LI measurement reporting for LTM execution. The UE stores the configurations, and the UE at step 503 transmits an RRC reconfiguration complete message to the gNB.

[0071] An early synchronization of the UE 110 with the LTM candidate cell(s) follows LTM preparation. As shown at steps 504A, 504B the UE performs early DL / UL synchronization with the LTM candidate cell(s). During early UL synchronization, the UE may perform early timing advance (TA) acquisition with the LTM candidate cell(s) as requested by the gNB 306 before receiving a cell switch command. This early synchronization may reduce interruption during LTM execution, as compared to L3 handover based mobility. In this regard, the TA may be used to control the timing of UL transmissions of a UE toward the LTM candidate cell(s). The UE may likewise have an acquired TA of the cell of the gNB to control the timing of UL transmissions toward the gNB.

[0072] During early UL synchronization at step 504B, the gNB 306 may trigger the UE to perform early TA acquisition via contention free random access (CFRA) by a physical downlink control channel (PDCCH) order (using downlink control information (DCI) format 1 0), following which the UE 110 sends a random access (RA) preamble on the physical RACH (PRACH) towards an indicated LTM candidate cell. In 3 GPP, the RA preamble is sent as a first message (msgl) as part of a RA procedure; and accordingly, the RA preamble may at times be referred to as msgl . In order to minimize the data interruption of the gNB due to CFRA towards the LTM candidate cell(s), the UE may not receive a random access response (RAR) from the network for the purpose of TA value acquisition, and the TA value of the LTM candidate cell may be indicated in a subsequent cell switch command.

[0073] During LTM execution, the UE 110 performs LI measurements on the configured LTM candidate cell(s), and the UE at step 505 transmits LI measurement reports to the gNB 306. In some examples, the LI measurements include LI reference signal received power (RSRP) measurements. In some of these examples, the LI measurement reports may be referred to as LI RSRP measurement reports.

[0074] The gNB 306 decides to execute a cell switch, and selects one of the LTM candidate cell(s) as a target cell for the cell switch. The gNB then at step 506 transmits a cell switch command (e.g., MAC control element (CE)), to trigger cell switch. The UE 110 switches to the configuration of the target cell; and if the TA of the target cell (from step 504B) is no longer available, the UE at step 507 initiates a RACH procedure with thetarget cell to acquire the TA of the target cell. The UE then at step 508 indicates successful completion of the cell switch. In this regard, the UE may transmit an RRC reconfiguration complete message to indicate completion of the cell switch. If the UE performed a RACH procedure at step 507, the UE may consider the cell switch execution successfully completed when the RACH procedure is successfully completed. For a RACH-less cell switch, the UE may consider the cell switch execution successfully completed when the UE determines that the RAN 108 has successfully received its first UL data.

[0075] The early DL / UL synchronization at steps 504a, 504b may be performed toward each configured candidate cell for subsequent LTM cell switch using the LTM candidate configuration(s) provided during LTM preparation at step 502.

[0076] Data packets such as packet data unit (PDUs) are transferred between the UE 208 and an external data network in a communication session referred to as a PDU session, which is a communication channel established to facilitate the exchange of data. The NGAP provides a signaling service between the gNB 306 and the AMF 308, and the NGAP supports a number of procedures, including UE context management procedures and PDU session management procedures.

[0077] The UE context management procedures include an initial UE context setup procedure to establish an initial UE context at the gNB 306, and when required, including PDU session context. During initial UE context setup, the AMF 308 may allocate a AMF UE NGAP identity (ID) (AMF-l JE-NGAP-ID) to uniquely identify the UE over the NG-C interface within the AMF. The UE context management procedures also include a UE context modification procedure to partially modify an established UE context, such as to modify or otherwise update the AMF UE NGAP ID to a new AMF UE NGAP ID.

[0078] The PDU session management procedures include a PDU session resource setup procedure to assign resources on the NG-U for one or more PDU sessions and corresponding quality of service (QoS) flows for a UE 110, and setup corresponding data radio bearer (DRBs) for the UE. The PDU session resource setup procedure may be performed during the initial UE context setup.

[0079] During setup of a PDU session, the SMF 310 may setup a NG-U transport bearer that forms a UP tunnel for routing UP data between the gNB 306 and UPF 312.The SMF may interact with the UPF to setup the UPF endpoint of the NG-U transport bearer for delivery of UL PDUs; and during PDU session resource setup, the AMF 308 may relay UP transport layer information (transport network layer (TNL) information) to the gNB that includes the UPF endpoint of the NG-U transport bearer (LL NG-U UP TNL Information). The gNB may in turn setup the gNB endpoint of the NG-U transport bearer for delivery of DL PDUs, and provide information (DL QoS Flow per TNL Information) that includes the gNB endpoint of the NG-U transport bearer, together with associated QoS flows, which the AMF may relay to the SMF.

[0080] One or more additional NG-U transport bearers for additional UP tunnels are setup for a single PDU session, such as for load balancing. When additional NG-U transport bearer(s) are setup, the gNB 306 may provide information (Additional DL QoS Flow per TNL Information) that includes the gNB endpoint(s) of the additional NG-U transport bearer(s), together with associated QoS flows. In the case of a split PDU session, the gNB may provide information (Additional Redundant DL QoS Flow per TNL Information) that includes the gNB endpoint(s) of the additional NG-U transport bearer(s) for delivery of redundant DL PDUs for split PDU session. The AMF 308 may in turn relay UP transport layer information to the gNB that includes the UPF endpoint(s) for the additional NG-U transport bearer(s) for the delivery of UL PDUs (Additional UL NG-U UP TNL Information), or the UPF endpoint(s) for the additional NG-U transport bearer(s) for delivery of redundant UL PDUs for a split PDU session (Additional Redundant UL NG-U UP TNL Information).

[0081] The UPF endpoint of one or more NG-U transport bearers for one or more UP tunnels, and the corresponding UP transport layer information, may change during a handover of the UE 110. In particular, for example, the UPF endpoint may change during an Xn-based inter NG-RAN handover with insertion of an intermediate UPF 312 (I- UPF), or during an Xn-based inter NG-RAN handover with re-allocation of an intermediate UPF. During these handover procedures, when an I-UPF is inserted or reallocated during a path switch procedure, the UPF endpoint of one or more NG-U transport bearers (and the corresponding UL NG-U UP TNL Information, Additional UL NG-U UP TNL Information and / or Additional Redundant UL NG-U UP TNL Information) may be changed, modified or otherwise updated.

[0082] In inter-CU subsequent cell change, in the context of LTM, the source gNB 306A prepares the candidate (target) gNBs 306B, and the source gNB provides the candidate gNBs with information for the target gNBs to communicate with the AMF 308 and UPF 312 after LTM execution or subsequent LTM execution. But after inter-CU LTM candidate preparation, it may be possible that some of the information to be modified at the source gNB, leaving the candidate gNBs with outdated information. This may in turn lead to release of the UE context of UL traffic drop during LTM execution or subsequent LTM execution. A similar problem exists in Similar problem persists for CHO.

[0083] FIGS. 6 A, 6B and 6C illustrate a signaling chart 600 for a conventional LTM procedure in which the AMF UE NGAP ID allocated to the UE 110 is modified to a new AMF UE NGAP ID. As shown in FIGS. 6A and 6B, UE context within the source gNB 306A contains information regarding roaming and access restrictions which were provided by the AMF 308 either at connection establishment or at the last timing advance (TA) update. The source gNB at step 601 configures UE measurement procedures, and the UE sends a L3 measurement report to the source gNB according to the measurement configuration. The source gNB at step 602 decides to use LTM based on the L3 measurement report.

[0084] The source gNB 306A at step 603 issues a handover request message to one or more candidate (target) gNBs 306B with information to prepare the LTM at the target side. This information may be signaled between the source gNB and candidate (target) gNBs according to the XnAP, and the information may include UE context information, such as a NG-C UE associated signaling reference (ng-c-UE-reference) with the AMF UE NGAP ID, allocated at the AMF on the source NG-C connection. The UE context information may also include PDU session resource related, such as the UP transport layer information that indicates the UPF endpoint(s) of the NG-U transport bearer and any additional NG-U transport bearer(s) (UL NG-U UP TNL Information at UPF . This information may include UL NG-U UP TNL Information, Additional UL NG-U UP TNL Information, and / or Additional Redundant UL NG-U UP TNL Information.

[0085] The candidate (target) gNBs 306B at step 604 store the information provided by the source gNB 306A, and the candidate (target) gNBs at step 605 perform admissioncontrol. The candidate (target) gNBs prepare the handover with L1 / L2, and the candidate (target) gNBs at step 606 send a handover request acknowledge message to the source gNB.

[0086] The source gNB 306A receives RRC reconfiguration(s) for the configured candidate (target) gNBs 306B, and the source gNB at step 607 provides the configuration(s) to the UE 110 by a RRC reconfiguration. The source gNB also configures the UE with LI measurement reporting for LTM execution. The UE at step 608 returns a RRC reconfiguration complete to the source gNB.

[0087] In some scenarios, the AMF 308 at step 609 sends a NGAP UE context modification request to modify the AMF UE NGAP ID to a new AMF UE NGAP ID NewAMF-UE-NGAP-ID at source gNB 306A before execution of a LTM cell switch. The source gNB at step 610 updates the AMF UE NGAP ID to the new AMF UE NGAP ID in the UE context. The candidate (target) gNBs 306B, however, will still have the earlier (now outdated) AMF UE NGAP ID earlier shared by the source gNB during preparation, as shown at step 611. The source gNB at step 612 sends a UE context modification response to the AMF.

[0088] As shown in FIG. 6C, during LTM execution, the UE 110 at step 613 performs LI measurements on the configured candidate (target) gNBs 306B, and sends LI measurement reports to the source gNB 306A. The source gNB at steps 614 and 615 decides to initiate a cell change to one of the candidate (target) gNBs as the target gNB, and sends a cell switch command (e.g., MAC-CE) to trigger the cell switch. The source gNB at step 616 sends a SN status transfer message to the target gNB.

[0089] The UE 110 at steps 617, 618 synchronizes to a cell of the target gNB 306B, and completes the LTM cell switch by sending a RRC reconfiguration complete message to target gNB. The target gNB at step 619 sends a handover success message to the source gNB 306B.

[0090] The target gNB 306B at step 620 sends a path switch request message to the AMF 308 to trigger the 5GC 302 to switch the DL data path towards the target gNB and to establish an NG-C interface instance towards the target gNB. But because the target gNB still has outdated AMF UE NGAP ID, the target gNB will use the outdated AMF UE NGAP ID in the path switch request message. The AMF may be unable to identify theUE by the outdated AMF UE NGAP ID, and the path switch procedure may fail. The AMF at step 622 sends a path switch failure message to the target gNB. And due to the path switch failure, the target gNB may release the UE, as shown at step 623.

[0091] FIGS. 7 A and 7B illustrate a signaling chart 700 for a conventional LTM procedure in which one or more UPF endpoints of the NG-U transport bearer or additional NG-U transport bearer(s) for the UE 110 are modified. As shown, the procedure includes handover preparation, as explained above at steps 601-608. As explained above, the handover preparation includes the source gNB 306A at step 603 issuing the handover request message to the candidate (target) gNB(s) 306B with information to prepare the LTM at the target side, including the UP transport layer information that indicates the UPF endpoint(s) of the NG-U transport bearer and any additional NG-U transport bearer(s) (UL NG-U UP TNL Information at UPF .

[0092] In some scenarios, UP transport layer information for a given PDU session may be updated after initial LTM preparation or during a path switch procedure after execution of the LTM cell switch to the target gNB 306B.

[0093] In a second scenario, before execution of the LTM cell switch, as shown at 709, the AMF 308 / SMF 310 may modify or add additional NG-U transport bearers for a given PDU session after initial LTM preparation or during a path switch procedure after execution of the LTM cell switch to the target gNB 306B.

[0094] As shown, after initial LTM preparation, more than one NG-U transport bearer may be setup for a single PDU session, and flows may be mapped to each NG-U transport bearer, as shown at steps 710, 711. The source gNB 306A at step 712 sends a PDU session resource modification indication message that includes information for the gNB endpoints of the NG-U transport bearers (DL QoS Flow per TNL Information, Additional DL QoS Flow per TNL Information), together with associated QoS flows. The AMF 308 at step 713 sends a PDU session resource modification confirm message that includes information for the UPF endpoints of the NG-U transport bearers (UL NG-U UP TNL Information, Additional UL NG-U UP TNL Information).

[0095] As shown at steps 714, 715, LTM cell switch (handover) of the UE 110 to the target gNB 306B is executed, and the UE completes the LTM cell switch by sending aRRC reconfiguration complete message to target gNB, such as in the manner described above at steps 613-618.

[0096] In a first scenario in which UP transport layer information for a given PDU session may be updated, after execution of the LTM cell switch, as shown at 716, the AMF 308 / SMF 310 may at step 717 modify or add additional NG-U transport bearers in case of insertion or re-allocation of a UPF 312. Again, after the LTM cell switch, the target gNB at step 718 sends a handover success message to the source gNB 306B. The second scenario in which the AMF 308 / SMF 310 may modify or add additional NG-U transport bearers for a given PDU session is shown again at step 719.

[0097] Upon completion of the LTM cell switch, the target gNB 306B at step 720 sends a path switch request message to the AMF 308 to trigger the 5GC 302 to switch the DL data path towards the target gNB and to establish an NG-C interface instance towards the target gNB. The 5GC switches the DL data path towards the target gNB, as shown at step 721. As shown in FIG. 7B, the UPF 312 at step 722 sends one or more “end marker” packets on the old path to the source gNB 306A per PDU session / tunnel and then can release any UP / TNL resources towards the source gNB.

[0098] As shown at 723, UL user data from the UE 110 is sent by the target gNB 306B (new serving or source gNB) using stored UP transport layer information (NG-U tunnel information). In the second scenario in which the UP transport layer information is modified after initial LTM preparation (and after the information is sent to the target gNB at step 603), the stored UP transport layer information at the target gNB may be outdated. This may make it more likely that the new serving / source gNB sends the UL user data to an incorrect UL NG-U TNL address (UPF endpoint).

[0099] In some examples, the second scenario (NG-U transport bearers modified or added) occurs after the path switch, as shown at 724, now with the target gNB 306B being the new serving / source gNB for the UE. In these examples, the new serving / source gNB may at step 725 receive updated UP transport layer information. But the other candidate (target) gNBs, as well as the former source gNB 306A, will still have the earlier (now outdated) UP transport layer information.

[0100] Sometime later, as shown at steps 726, 727, a subsequent LTM cell switch (handover) of the UE 110 to another candidate (target) gNB 306B is executed, and theUE completes the LTM cell switch by sending a RRC reconfiguration complete message to other target gNB, such as in the manner described above at steps 613-618. The other target gNB at step 728 sends a handover success message to the new serving / source gNB.

[0101] In the first scenario, involving insertion or re-allocation of the UPF 312, the UP transport layer information (UL NG-U UP TNL Information) may get updated in a path switch acknowledge message during the path switch procedure. But if the other target gNB (now the new serving / source gNB) starts to send the UL user data immediately after the UE 110 connects to the new serving / source gNB, before completion of path switch procedure, some of the UL user data may be lost to an incorrect UL NG-U UP TNL address (UPF endpoint). This is shown for the first scenario at 729 that includes the UE at step 730 sending UL user data.

[0102] As shown at step 731, the other target gNB 306B sends a path switch request message to the AMF 308 to trigger the 5GC 302 to switch the DL data path towards the other target gNB and to establish an NG-C interface instance towards the other target gNB. The 5GC switches the DL data path towards the target gNB, as shown at step 732. The UPF 312 at step 733 sends one or more “end marker” packets on the old path to the former serving / source gNB per PDU session / tunnel and then can release any UP / TNL resources towards the former serving / source gNB.

[0103] The AMF 308 at step 734 confirms the path switch request message with a path switch request acknowledge message to the other target gNB 306B, as the new serving / source gNB. And upon reception of the path switch request acknowledge message from the AMF, the other target gNB 306B (new serving / source gNB) at step 735 sends a UE context release so that the source gNB 306A can then release radio and CP- related resources associated to the UE context. Any ongoing data forwarding may continue.

[0104] In view of the foregoing problem s, example implementations of the present disclosure provide a solution in which the source gNB 306A may forward, to one or more candidate (target) gNBs 306B, an update to parameter(s) of one or more access node - CN interfaces related to the UE, which the source gNB may receive from the AMF 308. The update may be sent by a Xn interface message, and include an update of parameter(s) of the gNB-AMF interface (NG-C), such as the AMF UE NGAP ID. Additionally oralternatively, the update may include an update of param eter(s) of the gNB-UPF interface (NG-U), such as UP transport layer information (e.g., UL NG-U UP TNL Information, Additional UL NG-U UP TNL Information, Additional Redundant UL NG-U UP TNL Information). Similarly, in some examples, a target of a handover may recei ve an update of one or more parameters, such as UP transport layer information, and forward the update to other candidate (target) gNBs 306B or the earlier source gNB. The solution of example implementations may apply to a number of different handover techniques, including LTM and CHO.

[0105] In some examples, the source gNB 306A may instead inform the AMF 308 about a configured handover, which may enable the AMF to avoid updating the parameter(s) of the access node -- CN interface(s) while the handover remains configured. In particular, for example, the source gNB may send a message to the AMF that indicates the handover of the UE 110 is configured to enable the AMF to avoid the update to the parameter(s) while the handover is configured

[0106] FIGS. 8A and 8B illustrate a signaling chart 800 for a LTM procedure in which the AMF UE NGAP ID allocated to the UE 110 is modified to a new AMF UE NGAP ID, according to some example implementations. As shown, the LTM procedure includes handover preparation, as explained above at steps 601-608. As explained above, the handover preparation includes the source gNB 306A at step 603 issuing the handover request message to the candidate (target) gNB(s) 306B with information to prepare the LTM at the target side, including a NG-C UE associated signaling reference (ng-c-UE- reference) with the AMF UE NGAP ID AMF-UE-NGAP-ID).

[0107] As before, in some scenarios, the AMF 308 at step 609 sends a NGAP UE context modification request to modify the AMF UE NGAP ID to a new AMF UE NGAP ID (New AMF-UE-NGAP-ID), at source gNB 306A before execution of a LTM cell switch. The source gNB at step 810 updates the AMF UE NGAP ID to the new AMF UE NGAP ID in the UE context. According to some example implementations, the source gNB at step 811 also forwards the new AMF UE NGAP ID to the candidate (target) gNBs 306B. In some examples, the source gNB forwards the AMF UE NGAP ID in a message, such as a Xn interface class 1 or class 2 message. The candidate (target) gNBs at step 812 update their stored AMF UE NGAP ID to the new AMF UE NGAP ID. Inthis regard, the candidate (target) gNBs may update their stored NG-C UE associated signaling reference (ng-c-UE-reference) with the new AMF UE NGAP ID (NewAMF- UE-NGAP-ID). The source gNB at step 813 sends a UE context modification response to the AMF.

[0108] As shown in FIG. 8B, the LTM procedure may include LTM execution at steps 814-820 (including steps 813, 814, 815, 816, 817, 818, 819 and 820), which correspond to steps 613-619 described above. The target gNB 306B at step 821 sends a path switch request message to the AMF 308 to trigger the 5GC 302 to switch the DL data path towards the target gNB and to establish an NG-C interface instance towards the target gNB. As shown at step 822, the target gNB may use the new AMF UE NGAP ID while sending the path switch request message. The 5GC switches the DL data path towards the target gNB, and the AMF at step 823 confirms the path switch request message with a path switch request acknowledge message. The handover may then be completed at step 824.

[0109] As shown in signaling chart 800, in some examples, the source gNB 306A may forward the new AMF UE NGAP ID to all of the candidate (target) gNBs 306B. In other examples, the source gNB may forward the new AMF UE NGAP ID to only the target gNB of the candidate (target) gNBs. In this regard, FIGS. 9 A and 9B illustrate a signaling chart 900 for a LTM procedure in which the AMF UE NGAP ID allocated to the UE 110 is modified to a new AMF UE NGAP ID, according to other example implementations.

[0110] As shown in FIG. 9A, the LTM procedure includes handover preparation, as explained above at steps 601-608, including the handover request message with a NG-C UE associated signaling reference (ng-c-UE-reference with the AMF UE NGAP ID (AMF-UE-NGAP-ID). Also as before, the AMF 308 at step 609 sends a NGAP UE context modification request to modify the AMF UE NGAP ID to a new AMF UE NGAP ID (NewAMF-UPANGAP-ID), at source gNB 306A before execution of a LTM cell switch. The source gNB updates the AMF UE NGAP ID to the new AMF UE NGAP ID in the UE context The source gNB at step 910 sends a UE context modification response to the AMF.

[0111] During LTM execution, the UE 110 at step 911 performs LI measurements on the configured candidate (target) gNBs 306B, and sends LI measurement reports to the source gNB 306A. The source gNB at steps 912 and 913 decides to initiate a cell change to one of the candidate (target) gNBs as the target gNB, and sends a cell switch command (e.g., MAC-CE) to trigger the cell switch. The source gNB at step 914 also forwards the new AMF UE NGAP ID to the target gNB 306B. The source gNB may forward the new AMF UE NGAP ID in a Xn interface class 1 or class 2 message. In a more particular example, the new AMF UE NGAP ID may be included in a XnAP LTM cell switch message from the source gNB to the target gNB. The target gNB at step 812 updates its stored AMF UE NGAP ID to the new AMF UE NGAP ID. In this regard, the target gNB may update its stored NG-C UE associated signaling reference ng-c-UE-reference) with the new AMF UE NGAP ID (NewAMF-UE-NGAP-ID). As shown in FIG. 9B, the source gNB at step 915 sends a SN status transfer message to the target gNB.

[0112] The UE 110 at steps 916, 917 synchronizes to a cell of the target gNB 306B, and completes the LTM cell switch by sending a RRC reconfiguration complete message to target gNB. The target gNB at step 918 sends a handover success message to the source gNB 306B.

[0113] Similar to before, the target gNB 306B at step 919 sends a path switch request message to the AMF 308 to trigger the 5GC 302 to switch the DL data path towards the target gNB and to establish an NG-C interface instance towards the target gNB. As shown at step 920, the target gNB may use the new AMF UE NGAP ID while sending the path switch request message. The 5GC switches the DL data path towards the target gNB, and the AMF at step 921 confirms the path switch request message with a path switch request acknowledge message. The handover may then be completed at step 922.

[0114] Some example implementations provide a solution to the problems caused by scenarios in which UP transport layer information (e.g., UL NG-U UP TNL Information, Additional UL NG-U UP TNL Information, Additional Redundant UL NG-U UP TNL Information) for a given PDU session may be updated. Again, in a first scenario, after execution of a LTM cell switch, the AMF 308 / SMF 310 may modify or add additional NG-U transport bearers in case of insertion or re-allocation of a UPF 312. In a second scenario, before execution of the LTM cell switch, the AMF / SMF may modify or addadditional NG-U transport bearers for a given PDU session after initial LTM preparation or during a path switch procedure after execution of the LTM cell switch .

[0115] FIGS. 10A and 10B illustrate a signaling chart 1000 for a LTM procedure that provides a solution in the first scenario in which UP transport layer information for the UE 110 is modified, according to some example implementations. As shown in FIG.10A, the LTM procedure includes handover preparation, as explained above at steps 601- 608. As explained above, the handover preparation includes the source gNB 306A at step 603 issuing the handover request message to the candidate (target) gNB(s) 306B with information to prepare the LTM at the target side, including UP transport layer information.

[0116] As shown at steps 1009, 1010, LTM cell switch (handover) of the UE 110 to the target gNB 306B is executed, and the UE completes the LTM cell switch by sending a RRC reconfiguration complete message to target gNB, such as in the manner described above at steps 613-618. The target gNB 306B at step 1011 sends a handover success message to the source gNB 306A.

[0117] As shown at step 1012, the target gNB 306B sends a path switch request message to the AMF 308 to trigger the 5GC 302 to switch the DL data path towards the other target gNB and to establish an NG-C interface instance towards the other target gNB. The 5GC switches the DL data path towards the target gNB, as shown at step 732. The UPF 312 at step 733 sends one or more “end marker” packets on the old path to the former serving / source gNB per PDU session / tunnel and then can release any UP / TNL resources towards the former serving / source gNB.

[0118] The AMF 308 at step 1016 confirms the path switch request message with a path switch request acknowledge message to the target gNB 306B (as the new serving / source gNB). In the path switch request acknowledge message, the AMF provides an update to the UP transport layer information (e.g., UL NG-U UP TNL Information) to the new serving / source gNB. The new serving / source gNB at steps 1017, 1018 updates its UP transport layer information, and forwards the update to the UP transport layer information to the other candidate (target) gNBs, as well as the former source gNB 306A. The other candidate (target) gNBs and source gNB at step 1019 store the update to the UP transport layer information in UE context information for the UE.

[0119] Sometime later, as shown at steps 1020, 1021, a subsequent LTM cell switch (handover) of the UE 110 to another candidate (target) gNB 306B is executed, and the UE completes the LTM cell switch by sending a RRC reconfiguration complete message to other target gNB, such as in the manner described above at steps 613-618. The other target gNB at step 1022 sends a handover success message to the new serving / source gNB.

[0120] The UE 110 at step 1023 sends UL user data. As the other target gNB 306B previously received the update to the UP transport layer information, the other target gNB may use it to transfer the UL user data on to the UPF 312.

[0121] As also shown, the other target gNB 306B at step 1024 sends a path switch request message to the AMF 308 to trigger the 5GC 302 to switch the DL data path towards the other target gNB and to establish an NG-C interface instance towards the other target gNB. The 5GC switches the DL data path towards the target gNB, as shown at step 1025. The UPF 312 at step 1026 sends one or more “end marker” packets on the old path to the former serving / source gNB per PDU session / tunnel and then can release any UP / TNL resources towards the former serving / source gNB. And the AMF at step 1027 confirms the path switch request message with a path switch request acknowledge message to the other target gNB 306B, as the new serving / source gNB.

[0122] FIGS. 11 A and 1 IB illustrate a signaling chart 1100 for a LTM procedure that provides a solution in the second scenario in which UP transport layer information for the UE 110 is modified, according to some example implementations. As shown in FIG.11 A, the LTM procedure includes handover preparation, as explained above at steps 601- 608. As explained above, the handover preparation includes the source gNB 306A at step 603 issuing the handover request message to the candidate (target) gNB(s) 306B with information to prepare the LTM at the target side, including UP transport layer information.

[0123] As shown in FIG. 11 A, after initial LTM preparation, more than one NG-U transport bearer may be setup for a single PDU session, and flows may be mapped to each NG-U transport bearer, as shown at steps 1113, 1114. The source gNB 306A at step 1115 sends a PDU session resource modification indication message that includes information for the gNB endpoints of the NG-U transport bearers DL QoS Flow per TNLInformation, Additional DL QoS Flow per TNL Information), together with associ ated QoS flows. The AMF 308 at step 1116 sends a PDU session resource modification confirm message that includes informati on for the UPF endpoints of the NG-U transport bearers (UL NG-U UP TNL Information, Additional UL NG-U UP TNL Information). The source gNB at step 1117 forwards the updated UP transport layer information to the candidate (target) gNBs 306B.

[0124] As shown in FIG. 1 IB, at steps 1118, 1119, LTM cell switch (handover) of the UE 110 to the target gNB 306B is executed, and the UE completes the LTM cell switch by sending a RRC reconfiguration complete message to target gNB, such as in the manner described above at steps 613-618. The target gNB at step 1120 sends a handover success message to the source gNB 306B. As shown at 1121, the target gNB at this point has the updated UP transport layer information (e.g., UL NG-U UP TNL Information, Additional UL NG-U UP TNL Information), which the target gNB may use to route UL user data from the UE 110.

[0125] The target gNB 306B at step 1122 sends a path switch request message to the AMF 308 to trigger the 5GC 302 to switch the DL data path towards the other target gNB and to establish an NG-C interface instance towards the other target gNB. The 5GC switches the DL data path towards the target gNB, as shown at step 1123. The UPF 312 at step 1124 sends one or more “end marker” packets on the old path to the former serving / source gNB per PDU session / tunnel and then can release any UP / TNL resources towards the former serving / source gNB.

[0126] As also shown, UL user data from the UE 110 may be sent to the target gNB 306B. As the target gNB 306B previously received the update to the UP transport layer information, the target gNB may use it at step 1125 to transfer the UL user data on to the UPF 312. The AMF at step 1127 confirms the path switch request message with a path switch request acknowledge message to the other target gNB 306B, as the new serving / source gNB. The handover may then be completed at step 1128.

[0127] As indicated above, the solution of example implementations may apply to a number of different handover techniques, including LTM and CHO.

[0128] FIGS. 12A and 12B illustrate a signaling chart 1200 of a CHO procedure in which the AMF UE NGAP ID allocated to the UE 110 is modified to a new AMF UENGAP ID, according to some example implementation. As shown, the CHO procedure includes handover preparation, as explained above at steps 401-408. The handover preparation for CHO includes the source gNB 306A at step 404 issuing the handover request message to the candidate (target) gNB(s) 306B. Similar to the LTM procedure, the handover request message may include information to prepare the CHO at the target side, including a NG-C UE associated signaling reference (ng-c-UE-reference) with the AMF UE NGAP ID (AMF-UE-NGAP-ID).

[0129] As before, in some scenarios, the 5GC 302 (AMF 308) at step 1209 sends a NGAP UE context modification request to modify the AMF UE NGAP ID to a new AMF UE NGAP ID (New AMF-UE-NGAP-ID), at source gNB 306A before execution of the handover. The source gNB at step 1210 updates the AMF UE NGAP ID to the new AMF UE NGAP ID in the UE context.

[0130] The source gNB 306A at step 1211 also forwards the new AMF UE NGAP ID to the candidate (target) gNBs 306B. The source gNB may forward the new AMF UE NGAP ID in a handover request with CHO replace indication, or by separate messaging that includes a new NG-C UE associated signaling reference (ng-c-UE-reference) with the new AMF UE NGAP ID (New AMF-UE-NGAP-ID). The candidate (target) gNBs at step 1212 update their stored AMF UE NG AP ID to the new AMF UE NGAP ID. In this regard, the candidate (target) gNBs may update their stored NG-C UE associated signaling reference (ng-c-UE-reference) with the new AMF UE NGAP ID (NewAMF- UE-NCiAP-ID). The source gNB at step 1213 sends a UE context modification response to the AMF.

[0131] As shown in FIG. 12B, the CHO procedure may include CHO execution at steps 1214-1221 (including steps 1214, 1215, 1216, 1217, 1218, 1219, 1220 and 1221), which correspond to steps 410-416 described above.

[0132] The target gNB 306B at step 1223 sends a path switch request message to the 5GC 302 (AMF 308) to trigger the 5GC to switch the DL data path towards the target gNB and to establish an NG-C interface instance towards the target gNB. As shown at step 1223, the target gNB may use the new AMF UE NGAP ID while sending the path switch request message. The 5GC switches the DL data path towards the target gNB, and the 5GC at step 1224 confirms the path switch request message with a path switchrequest acknowledge message. And upon reception of the path switch request acknowledge message from the 5GC, the target gNB 306B (new serving / source gNB) at step 1225 sends a UE context release so that the source gNB 306A can then release radio and CP -related resources associated to the UE context. Any ongoing data forwarding may continue.

[0133] FIG. 13 illustrate a signaling chart 1300 of a CHO procedure in which the AMF UE NGAP ID allocated to the UE 110 is modified to a new AMF UE NGAP ID, according to some example implementation. As shown in FIG. 10A, the CHO procedure includes handover preparation, as explained above at steps 401-408. As explained above, the handover preparation includes the source gNB 306A at step 603 issuing the handover request message to the candidate (target) gNB(s) 306B with information to prepare the CHO at the target side, including UP transport layer information (e.g., UL NG-U UP TNL Information, Additional UL NG-U UP TNL Information, Additional Redundant UL NG-U UP TNL Information) for a given PDU session. The CHO procedure also includes handover execution, as explained above at steps 419-417.

[0134] The UE at step 1318 sends UL user data, which the target gNB 306B routes to 5GC (UPF 312) using the UP transport layer information received during CHO preparation.

[0135] The target gNB 306B at step 1319 sends a path switch request message to the 5GC 302 (AMF 308) to trigger the 5GC to switch the DL data path towards the target gNB and to establish an NG-C interface instance towards the target gNB. The 5GC switches the DL data path towards the target gNB, and the 5GC at step 1321 confirms the path switch request message with a path switch request acknowledge message. In the path switch request acknowledge message, the 5GC (AMF) provides an update to the UP transport layer information (e.g., UL NG-U UP TNL Information) to the target gNB as the new serving / source gNB. The new serving / source gNB at steps 1322, 1323 updates its UP transport layer information, and forwards the update to the UP transport layer information to the former source gNB 30 A, and may also forward the update to the other candidate (target) gNBs. The source gNB (and other candidate (target) gNBs) at step 1324 stores the update to the UP transport layer information in UE contextinformation for the UE 110, such as for use during a subsequent handover of the UE, as described above.

[0136] FIGS. 14A and 14B are flowcharts illustrating various steps in a method 1400 according to various example implementations. The method includes configuring at block 1402 a handover of a user equipment (UE) in which a handover request message is sent to candidate access nodes to prepare for the handover, the handover request message including one or more parameters of one or more of an access node - access and mobility management function (AMF) interface, or an access node - user plane function (UPF) interface, related to the UE. The method includes receiving at block 1404 a UE-related request message from an AMF that includes an update to at least one of the one or more parameters of the at least one of the access node - AMF interface or the access node - UPF interface. And the method includes forwarding the update to the at least one of the one or more parameters to at least one of the candidate access nodes for use by a target access node of the at least one of the candidate access nodes in connection with the handover, as shown at block 1406 of FIG. 14 A.

[0137] In some examples, the one or more parameters include one or more parameters of an access node - AMF interface related to the UE, and the UE-related request message includes an update to at least one of the one or more parameters of the access node - AMF interface. In some of these examples, the update to the at least one of the one or more parameters is forwarded at block 1406 to the at least one of the candidate access nodes for use by the target access node for a path switch with the AMF.

[0138] In some examples, the one or more parameters of the access node - AMF interface include an identifier of the UE over the access node - AMF interface within the AMF.

[0139] In some examples, configuring at block 1402 the handover of the UE includes at least configuring a lower-layer triggered mobility (LTM) cell switch of the UE.

[0140] In some examples, the update to the at least one of the one or more parameters is forwarded at block 1406 to all of the candidate access nodes.

[0141] In some examples, the method 1400 further includes at least making a decision to execute the LTM cell switch of the UE to the target access node, as shown atblock 1408 of FIG. 14B. In some of these examples, the update to the at least one of the one or more parameters is forwarded at block 1406 only to the target access node.

[0142] In some examples, configuring at block 1402 the handover of the UE includes at least configuring a conditional handover of the UE.

[0143] In some examples, the update to the at least one of the one or more parameters is forwarded at block 1406 to all of the candidate access nodes.

[0144] In some examples, the one or more parameters include user plane transport layer information for the access node - UPF interface related to the UE, and the UE- related request message includes an update to the user plane transport layer information. In some of these examples, the update to the user plane transport layer information is forwarded at block 1406 to the at least one of the candidate access nodes for use by the target access node for routing uplink data.

[0145] FIG. 15 is a flowchart illustrating various steps in a method 1500 according to various example implementations. The method includes configuring a handover of a user equipment (UE) in which a handover request message is sent to candidate access nodes to prepare the candidate access nodes for the handover, the handover request message including one or more parameters of an access node - access and mobility management function (AMF) interface related to the UE, as shown at block 1502. The method includes receiving a UE-related request message from an AMF that includes an update to at least one of the one or more parameters of the access node - AMF interface related to the UE, as shown at block 1504. And the method includes sending a message to the AMF that indicates the handover of the UE is configured to enable the AMF to avoid the update to the at least one of the one or more parameters while the handover is configured, as shown at block 1506.

[0146] FIGS. 16A and 16B are flowcharts illustrating various steps in a method 1600 according to various example implementations. The method includes receiving a handover request message from a source access node during preparation of candidate access nodes for a handover of a user equipment (UE), the handover request message including user plane transport layer information for an access node - user plane function (UPF) interface related to the UE, as shown at block 1602 of FIG. 16 A. The method includes carrying out the handover of the UE, as shown at block 1604. The methodincludes carrying out a path switch procedure with an access and mobility function (AMF), in connection with the handover, and during which an update to the user plane transport layer information is received from the AMF, as shown at block 1606. And the method includes forwarding the update to the user plane transport layer information to one or more of the candidate access nodes for use by a target access node of the one or more candidate access nodes in connection with a subsequent handover, as shown at block 1608.

[0147] In some examples, the method 1600 further includes forwarding the update of the user plane transport layer information to the source access node as a candidate access node for the subsequent handover, as shown at block 1610 of FIG. 16B.

[0148] In some examples, carrying at block 1604 out the handover includes carrying out a lower-layer triggered mobility (LTM) cell switch of the UE.

[0149] In some examples, carrying at block 1604 out the handover includes carrying out a conditional handover of the UE.

[0150] According to example implementations of the present disclosure, a telecommunications system 100 or PLMN 102, and its components such as a UE 110, CN 106, RAN 108, radio access node 202, 5GC 302, gNB 306, source gNB 306A, target gNB 306B, AMF 308, SMF 310 and / or UPF 312, may be implemented by various means. Means for implementing the system and its components may include hardware, firmware, software, or combinations thereof. In some examples, one or more apparatuses may be configured to function as or otherwise implement the system and its components shown and described herein. In examples involving more than one apparatus, the respective apparatuses may be connected to or otherwise in communication with one another in a number of different manners, such as directly or indirectly via a wired or wireless network or the like.

[0151] According to some example implementati ons, at least some of the method 1400 described with respect to FIGS. 14A and 14B may be carried out by an apparatus including means for performing functions corresponding steps of the method. Similarly, at least some of the method 1500 described with respect to FIG. 15 may be carried out by an apparatus including means for performing functions corresponding steps of the method. And at least some of the method 1600 described with respect to FIGS. 16A and16B may be carried out by an apparatus including means for performing functions corresponding steps of the method. Examples of a suitable apparatus may include a gNB (e.g., gNB-DU, gNB-CU), ng-eNB or any suitable apparatus, such as a server, host or node.

[0152] FIG. 17 illustrates an apparatus 1700 in which means for performing various functions includes hardware, alone or under direction of one or more computer programs from a computer-readable storage medium or other memory, such as computer memory, according to some example implementations of the present disclosure. The apparatus may include one or more of each of a number of components such as, for example, processing circuitry 1702 connected to computer-readable storage medium or other memory 1704.

[0153] The processing circuitry 1702 may be composed of one or more processors alone or in combination with one or more computer-readable storage media. The processing circuitry is generally any piece of computer hardware that is capable of processing information such as, for example, data, computer programs and / or other suitable electronic information. The processing circuitry is composed of a collection of electronic circuits some of which may be packaged as an integrated circuit or multiple interconnected integrated circuits (an integrated circuit at times more commonly referred to as a “chip”). The processing circuitry may be configured to execute computer programs, which may be stored onboard the processing circuitry or otherwise stored in the memory 1704 (of the same or another apparatus).

[0154] The processing circuitry 1702 may be a number of processors, a multi-core processor or some other type of processor, depending on the particular implementation. Further, the processing circuitry may be implemented using a number of heterogeneous processor systems in which a main processor is present with one or more secondary processors on a single chip. As another illustrative example, the processing circuitry may be a symmetric multi-processor system containing multiple processors of the same type. In yet another example, the processing circuitry may be embodied as or otherwise include one or more ASICs, FPGAs or the like. Thus, although the processing circuitry may be capable of executing a computer program to perform one or more functions, the processing circuitry of various examples may be capable of performing one or more functions without the aid of a computer program. In either instance, the processingcircuitry may be appropriately programmed to perform functions or operations according to example implementations of the present disclosure.

[0155] The memory 1704 is generally any piece of computer hardware that is capable of storing information such as, for example, data, computer programs, instructions 1706 (e.g., computer-readable program code) and / or other suitable information either on a temporary basis and / or a permanent basis. The memory may include volatile and / or nonvolatile memory, and may be fixed or removable. Examples of suitable memory include recording media, random access memory (RAM), read-only memory (ROM), a hard drive, a flash memory, a thumb drive, a removable computer diskette, an optical disk or some combination thereof.

[0156] The memory 1704 is a non-transitory device capable of storing information. One example of a suitable memory is a computer-readable storage medium, which is distinguishable from a computer-readable transmission medium capable of carrying information from one location to another. Examples of suitable computer-readable transmission media comprise electronic carrier signals, telecommunications signals, or some combination thereof. As used herein, the term “non-transitory” is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM versus ROM). A computer-readable medium as described herein generally refers to a computer-readable storage medium or computer-readable transmission medium. A computer-readable medium is any entity or device capable in which information, such as one or more computer programs or portions thereof, may be stored and carried.

[0157] In addition to the memory 1704 (e.g., computer-readable storage medium), the processing circuitry 1702 may also be connected to one or more interfaces for displaying, transmitting and / or receiving information. The interfaces may include a communications interface 1708 and / or one or more user interfaces (e.g., display, user input interface). The communications interface may be configured to transmit and / or receive information, such as to and / or from other apparatus(es), network(s) or the like. The communications interface may be configured to transmit and / or receive information by physical (wired) and / or wireless communications links. Examples of suitable communication interfaces include a network interface controller (NIC), wireless NIC (WNIC) or the like.

[0158] Execution of the instructions 1706 by the processing circuitry 1702, or storage of the instructi ons in the memory 1704, supports combinations of operations for implementing example implementations of the present disclosure. In this manner, an apparatus 1700 may comprise at least one processing circuitry and at least one memory coupled to the at least one processing circuitry, where the at least one processing circuitry is configured to execute instructions stored in the at least one memory. It will also be understood that one or more functions, and combinations of functions, may be implemented by special purpose hardware-based computer systems and / or processing circuitry which perform the specified functions, or combinations of special purpose hardware and program code instructions.

[0159] Some example implementati ons of the present disclosure may also be carried out in the form of a computer process defined by one or more computer programs or portions thereof. Example implementations of the present disclosure may be carried out by executing at least one portion of a computer program comprising instructions. The computer program may be in source code form, object code form, or in some intermediate form. The computer program may be stored in a computer-readable medium that is readable by a computer, processing circuitry or other suitable apparatus. As indicated above, for example, the computer program may be stored in a memory, such as a computer-readable storage medium. Additionally or alternatively, for example, the computer program may be stored in a computer-readable transmission medium. The coding of software for carrying out example implementations of the present di sclosure is well within the scope of a person of ordinary skill in the art.

[0160] As will be appreciated, any suitable instructions may be loaded onto a computer, a processing circuitry or other programmable apparatus from a memory or a computer-readable medium (e.g., computer-readable storage medium, computer-readable transmission medium) to produce a particular machine, such that the particular machine becomes a means for implementing the functions specified herein. The instructions may also be stored in a computer-readable medium that can direct a computer, a processing circuitry or other programmable apparatus to function in a particular manner to thereby generate a particular machine or particular article of manufacture. In some examples, the instructions stored in the computer-readable medium may produce an article ofmanufacture, where the article of manufacture becomes a means for implementing functions described herein. The instructions may be retrieved from a computer-readable medium and loaded into a computer, processing circuitry or other programmable apparatus to configure the computer, processing circuitry or other programmable apparatus to execute operations to be performed on or by the computer, processing circuitry or other programmable apparatus.

[0161] Retrieval, loading and execution of instructions including program code instructions may be performed sequentially such that one instruction is retrieved, loaded and executed at a time. In some example implementations, retrieval, loading and / or execution may be performed in parallel such that multiple instructions are retrieved, loaded, and / or executed together. Execution of the program code instructions may produce a computer-implemented process such that the instructions executed by the computer, processing circuitry or other programmable apparatus provide operations for implementing functions described herein.

[0162] As explained above and reiterated below, the present disclosure includes, without limitation, the following example implementations.

[0163] Clause 1. An apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: configure a handover of a user equipment (UE) in which a handover request message is sent to candidate access nodes to prepare for the handover, the handover request message including one or more parameters of one or more of an access node - access and mobility management function (AMF) interface, or an access node - user plane function (UPF) interface, related to the UE; receive a UE-related request message from an AMF that includes an update to at least one of the one or more parameters of the at least one of the access node -- AMF interface or the access node - UPF interface; and forward the update to the at least one of the one or more parameters to at least one of the candidate access nodes for use by a target access node of the at least one of the candidate access nodes in connection with the handover.

[0164] Clause 2. The apparatus of clause 1, wherein the one or more parameters include one or more parameters of an access node - AMF interface related to the UE, andthe UE-related request message includes an update to at least one of the one or more parameters of the access node -- AMF interface, and wherein the update to the at least one of the one or more parameters is forwarded to the at least one of the candidate access nodes for use by the target access node for a path switch with the AMF.

[0165] Clause 3. The apparatus of clause 2, wherein the one or more parameters of the access node AMF interface i nclude an i dentifier of the UE over the access node - AMF interface within the AMF.

[0166] Clause 4. The apparatus of clause 2 or clause 3, wherein the apparatus caused to configure the handover of the UE includes the apparatus caused to at least configuring a lower-layer triggered mobility (LTM) cell switch of the UE.

[0167] Clause 5. The apparatus of clause 4, wherein the update to the at least one of the one or more parameters is forwarded to all of the candidate access nodes.

[0168] Clause 6. The apparatus of clause 4 or clause 5, wherein the method further comprises at least making a decision to execute the LTM cell switch of the UE to the target access node, and the update to the at least one of the one or more parameters is forwarded only to the target access node.

[0169] Clause 7. The apparatus of any of clauses 2 to 6, wherein the apparatus caused to configure the handover of the UE includes the apparatus caused to at least configuring a conditional handover of the UE.

[0170] Clause 8. The apparatus of clause 7, wherein the update to the at least one of the one or more parameters is forwarded to all of the candidate access nodes.

[0171] Clause 9. The apparatus of any of clauses 1 to 8, wherein the one or more parameters include user plane transport layer information for the access node ~ UPF interface related to the UE, and the UE-related request message includes an update to the user plane transport layer information, and wherein the update to the user plane transport layer information is forwarded to the at least one of the candidate access nodes for use by the target access node for routing uplink data.

[0172] Clause 10. An apparatus comprising: means for configuring a handover of an user equipment (UE) in which a handover request message is sent to candidate access nodes to prepare for the handover, the handover request message including one or more parameters of one or more of an access node - access and mobility management function(AMF) interface, or an access node - user plane function (UPF) interface, related to the UE; means for receiving a UE-related request message from an AMF that includes an update to at least one of the one or more parameters of the at least one of the access node - AMF interface or the access node - UPF interface; and means for forwarding the update to the at least one of the one or more parameters to at least one of the candidate access nodes for use by a target access node of the at least one of the candidate access nodes in connection with the handover.

[0173] Clause 11. The apparatus of clause 10, wherein the one or more parameters include one or more parameters of an access node -- AMF interface related to the UE, and the UE-related request message includes an update to at least one of the one or more parameters of the access node -- AMF interface, and wherein the update to the at least one of the one or more parameters is forwarded to the at least one of the candidate access nodes for use by the target access node for a path switch with the AMF.

[0174] Clause 12. The apparatus of clause 11, wherein the one or more parameters of the access node ™ AMF interface include an identifier of the UE over the access node ™ AMF interface within the AMF.

[0175] Clause 13. The apparatus of clause 11 or clause 12, wherein the means for configuring the handover includes at least means for configuring a lower-layer triggered mobility (LTM) cell switch of the UE.

[0176] Clause 14. The apparatus of clause 13, wherein the update to the at least one of the one or more parameters is forwarded to all of the candidate access nodes.

[0177] Clause 15. The apparatus of clause 13 or clause 14, wherein the apparatus further comprises at least means for making a decision to execute the LTM cell switch of the UE to the target access node, and the update to the at least one of the one or more parameters is forwarded only to the target access node.

[0178] Clause 16. The apparatus of any of clauses 11 to 15, wherein the means for configuring the handover includes at least means for configuring a conditional handover of the UE.

[0179] Clause 17. The apparatus of clause 16, wherein the update to the at least one of the one or more parameters is forwarded to all of the candidate access nodes.

[0180] Clause 18. The apparatus of any of clauses 10 to 17, wherein the one or more parameters include user plane transport layer information for the access node -- UPF interface related to the UE, and the UE-related request message includes an update to the user plane transport layer information, and wherein the update to the user plane transport layer information is forwarded to the at least one of the candidate access nodes for use by the target access node for routing uplink data.

[0181] Clause 19. A method comprising: configuring a handover of a user equipment (UE) in which a handover request message is sent to candidate access nodes to prepare for the handover, the handover request message including one or more parameters of one or more of an access node -- access and mobility management function (AMF) interface, or an access node - user plane function (UPF) interface, related to the UE; receiving a UE-related request message from an AMF that includes an update to at least one of the one or more parameters of the at least one of the access node - AMF interface or the access node - UPF interface; and forwarding the update to the at least one of the one or more parameters to at least one of the candidate access nodes for use by a target access node of the at least one of the candidate access nodes in connection with the handover.

[0182] Clause 20. The method of clause 19, wherein the one or more parameters include one or more parameters of an access node - AMF interface related to the UE, and the UE-related request message includes an update to at least one of the one or more parameters of the access node - AMF interface, and wherein the update to the at least one of the one or more parameters is forwarded to the at least one of the candidate access nodes for use by the target access node for a path switch with the AMF.

[0183] Clause 21. The method of clause 20, wherein the one or more parameters of the access node - AMF interface include an identifier of the UE over the access node - AMF interface within the AMF.

[0184] Clause 22. The method of clause 20 or clause 21, wherein configuring the handover of the UE includes at least configuring a lower-layer triggered mobility (LTM) cell switch of the UE.

[0185] Clause 23. The method of clause 22, wherein the update to the at least one of the one or more parameters is forwarded to all of the candidate access nodes.

[0186] Clause 24. The method of clause 22 or clause 23, wherein the method further comprises at least making a decision to execute the LTM cell switch of the UE to the target access node, and the update to the at least one of the one or more parameters is forwarded only to the target access node.

[0187] Clause 25. The method of any of clauses 20 to 24, wherein configuring the handover of the UE includes at least configuring a conditional handover of the UE.

[0188] Clause 26. The method of clause 25, wherein the update to the at least one of the one or more parameters is forwarded to all of the candidate access nodes.

[0189] Clause 27. The method of any of clauses 19 to 26, wherein the one or more parameters include user plane transport layer information for the access node - UPF interface related to the UE, and the UE-related request message includes an update to the user plane transport layer information, and wherein the update to the user plane transport layer information is forwarded to the at least one of the candidate access nodes for use by the target access node for routing uplink data.

[0190] Clause 28. A computer-readable storage medium that is non-transitory and has instructions stored therein that, in response to execution by at least one processing circuitry, causes an apparatus to at least: configure a handover of a user equipment (UE) in which a handover request message is sent to candidate access nodes to prepare for the handover, the handover request message including one or more parameters of one or more of an access node - access and mobility management function (AMF) interface, or an access node - user plane function (UPF) interface, related to the UE; receive a UE- related request message from an AMF that includes an update to at least one of the one or more parameters of the at least one of the access node - AMF i nterface or the access node - UPF interface; and forward the update to the at least one of the one or more parameters to at least one of the candidate access nodes for use by a target access node of the at least one of the candidate access nodes in connection with the handover.

[0191] Clause 29. The computer-readable storage medium of clause 28, wherein the one or more parameters include one or more parameters of an access node - AMF interface related to the UE, and the UE-related request message includes an update to at least one of the one or more parameters of the access node - AMF interface, and wherein the update to the at least one of the one or more parameters is forwarded to the at leastone of the candidate access nodes for use by the target access node for a path switch with the AMF.

[0192] Clause 30. The computer-readable storage medium of clause 29, wherein the one or more parameters of the access node -- AMF interface include an identifier of the UE over the access node AMF interface within the AMF.

[0193] Clause 31. The computer-readable storage medium of clause 29 or clause 30, wherein the apparatus caused to configure the handover of the UE i ncludes the apparatus caused to at least configuring a lower-layer triggered mobility (LTM) cell switch of the UE.

[0194] Clause 32. The computer-readable storage medium of clause 31, wherein the update to the at least one of the one or more parameters is forwarded to all of the candidate access nodes.

[0195] Clause 33. The computer-readable storage medium of clause 31 or clause 32, wherein the method further comprises at least making a decision to execute the LTM cell switch of the UE to the target access node, and the update to the at least one of the one or more parameters is forwarded only to the target access node.

[0196] Clause 34. The computer-readable storage medium of any of clauses 29 to 33, wherein the apparatus caused to configure the handover of the UE includes the apparatus caused to at least configuring a conditional handover of the UE.

[0197] Clause 35. The computer-readable storage medium of clause 34, wherein the update to the at least one of the one or more parameters is forwarded to all of the candidate access nodes.

[0198] Clause 36. The computer-readable storage medium of any of clauses 28 to 35, wherein the one or more parameters include user plane transport layer information for the access node - UPF interface related to the UE, and the UE-related request message includes an update to the user plane transport layer information, and wherein the update to the user plane transport layer information is forwarded to the at least one of the candidate access nodes for use by the target access node for routing uplink data.

[0199] Clause 37. An apparatus comprising means for performing the method of any of clauses 19 to 27.

[0200] Clause 38. A computer-readable medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 19 to 27.

[0201] Clause 39. A computer-readable storage medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 19 to 27.

[0202] Clause 40. A computer program comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 19 to 27.

[0203] Clause 41. An apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: configure a handover of a user equipment (UE) in which a handover request message is sent to candidate access nodes to prepare the candidate access nodes for the handover, the handover request message including one or more parameters of an access node - access and mobility management function (AMF) interface related to the UE; receive a UE- related request message from an AMF that includes an update to at least one of the one or more parameters of the access node - AMF interface related to the UE; and send a message to the AMF that indi cates the handover of the UE is configured to enable the AMF to avoid the update to the at least one of the one or more parameters while the handover is configured.

[0204] Clause 42. An apparatus comprising: means for configuring a handover of an user equipment (UE) in which a handover request message is sent to candidate access nodes to prepare the candidate access nodes for the handover, the handover request message including one or more parameters of an access node -- access and mobility management function (AMF) interface related to the UE; means for receiving a UE- related request message from an AMF that includes an update to at least one of the one or more parameters of the access node -- AMF interface related to the UE; and means for sending a message to the AMF that indicates the handover of the UE is configured to enable the AMF to avoid the update to the at least one of the one or more parameters while the handover is configured.

[0205] Clause 43. A method comprising: configuring a handover of a user equipment (UE) in which a handover request message is sent to candidate access nodes to prepare the candidate access nodes for the handover, the handover request message including one or more parameters of an access node -- access and mobility management function (AMF) interface related to the UE; receiving a UE-related request message from an AMF that includes an update to at least one of the one or more parameters of the access node ™ AMF interface related to the UE; and sending a message to the AMF that indicates the handover of the UE is configured to enable the AMF to avoid the update to the at least one of the one or more parameters while the handover is configured.

[0206] Clause 44. A computer-readable storage medium that is non-transitory and has instructions stored therein that, in response to execution by at least one processing circuitry, causes an apparatus to at least: configure a handover of a user equipment (UE) in which a handover request message is sent to candidate access nodes to prepare the candidate access nodes for the handover, the handover request message including one or more parameters of an access node ™ access and mobility management function (AMF) interface related to the UE; receive a UE-related request message from an AMF that includes an update to at least one of the one or more parameters of the access node -- AMF interface related to the UE; and send a message to the AMF that indicates the handover of the UE is configured to enable the AMF to avoid the update to the at least one of the one or more parameters while the handover is configured.

[0207] Clause 45. A computer-readable medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of clause Clause 43.

[0208] Clause 46. A computer program comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of clause Clause 43.

[0209] Clause 47. An apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: receive a handover request message from a source access node during preparation of candidate access nodes for a handover of a user equipment (UE), the handover request messageincluding user plane transport layer information for an access node - user plane function (UPF) interface related to the UE; carry out the handover of the UE; carry out a path switch procedure with an access and mobility function (AMF), in connection with the handover, and during which an update to the user plane transport layer information is received from the AMF; and forward the update to the user plane transport layer information to one or more of the candidate access nodes for use by a target access node of the one or more candidate access nodes in connection with a subsequent handover.

[0210] Clause 48. The apparatus of clause 47, wherein the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further forward the update of the user plane transport layer information to the source access node as a candidate access node for the subsequent handover.

[0211] Clause 49. The apparatus of clause 47 or clause 48, wherein the apparatus caused to carry out the handover includes the apparatus caused to carry out a lower-layer triggered mobility (LTM) cell switch of the UE.

[0212] Clause 50. The apparatus of any of clauses 47 to 49, wherein the apparatus caused to carry out the handover includes the apparatus caused to carry out a conditional handover of the UE.

[0213] Clause 51. An apparatus comprising: means for receiving a handover request message from a source access node during preparation of candidate access nodes for a handover of an user equipment (UE), the handover request message including user plane transport layer information for an access node ™ user plane function (UPF) interface related to the UE; means for carrying out the handover of the UE; means for carrying out a path switch procedure with an access and mobility function (AMF), in connection with the handover, and during which an update to the user plane transport layer information is received from the AMF; and means for forwarding the update to the user plane transport layer information to one or more of the candidate access nodes for use by a target access node of the one or more candidate access nodes in connection with a subsequent handover.

[0214] Clause 52. The apparatus of clause 51, wherein the apparatus further comprises means for forwarding the update of the user plane transport layer information to the source access node as a candidate access node for the subsequent handover.

[0215] Clause 53. The apparatus of clause 51 or clause 52, wherein the means for carrying out the handover includes means for carrying out a lower-layer triggered mobility (LTM) cell switch of the UE.

[0216] Clause 54. The apparatus of any of clauses 51 to 53, wherein the means for carrying out the handover includes means for carrying out a conditional handover of the UE.

[0217] Clause 55. A method comprising: receiving a handover request message from a source access node during preparation of candidate access nodes for a handover of a user equipment (UE), the handover request message including user plane transport layer information for an access node - user plane function (UPF) interface related to the UE; carrying out the handover of the UE; carrying out a path switch procedure with an access and mobility function (AMF), in connection with the handover, and during which an update to the user plane transport layer information is received from the AMF; and forwarding the update to the user plane transport layer information to one or more of the candidate access nodes for use by a target access node of the one or more candidate access nodes in connection with a subsequent handover.

[0218] Clause 56. The method of clause 55, wherein the method further comprises forwarding the update of the user plane transport layer information to the source access node as a candidate access node for the subsequent handover.

[0219] Clause 57. The method of clause 55 or clause 56, wherein carrying out the handover includes carrying out a lower-layer triggered mobility (LTM) cell switch of the UE.

[0220] Clause 58. The method of any of clauses 55 to 57, wherein carrying out the handover includes carrying out a conditional handover of the UE.

[0221] Clause 59. A computer-readable storage medium that is non-transitory and has instructions stored therein that, in response to execution by at least one processing circuitry, causes an apparatus to at least: receive a handover request message from a source access node during preparation of candidate access nodes for a handover of a user equipment (UE), the handover request message including user plane transport layer information for an access node ™ user plane function (UPF) interface related to the UE; carry out the handover of the UE; carry out a path switch procedure with an access andmobility function (AMF), in connection with the handover, and during which an update to the user plane transport layer information is received from the AMF; and forward the update to the user plane transport layer information to one or more of the candidate access nodes for use by a target access node of the one or more candidate access nodes in connection with a subsequent handover.

[0222] Clause 60. The computer-readable storage medium of clause 59, wherein the computer-readable storage medium has further instructions stored therein that, in response to execution by the at least one processing circuitry, causes the apparatus to further forward the update of the user plane transport layer information to the source access node as a candidate access node for the subsequent handover.

[0223] Clause 61. The computer-readable storage medium of clause 59 or clause 60, wherein the apparatus caused to carry out the handover includes the apparatus caused to carry out a lower-layer triggered mobility (LTM) cell switch of the UE.

[0224] Clause 62. The computer-readable storage medium of any of clauses 59 to 61, wherein the apparatus caused to carry out the handover includes the apparatus caused to carry out a conditional handover of the UE.

[0225] Clause 63. An apparatus comprising means for performing the method of any of clauses 55 to 58.

[0226] Clause 64. A computer-readable medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 55 to 58.

[0227] Clause 65. A computer-readable storage medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 55 to 58.

[0228] Clause 66. A computer program comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 55 to 58.

[0229] Many modifications and other implementations of the disclosure set forth herein will come to mind to one skilled in the art to which the disclosure pertains having the benefit of the teachings presented in the foregoing description and the associated figures. Therefore, it is to be understood that the disclosure is not to be limited to thespecific implementations disclosed and that modifications and other implementations are intended to be included within the scope of the appended claims. Moreover, although the foregoing description and the associated figures describe example implementations in the context of certain example combinations of elements and / or functions, it should be appreciated that different combinations of elements and / or functions may be provided by alternative implementations without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and / or functions than those explicitly described above are also contemplated as may be set forth in some of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

WHAT IS CLAIMED IS:

1. An apparatus comprising: means for configuring a handover of an user equipment (UE) in which a handover request message is sent to candidate access nodes to prepare for the handover, the handover request message including one or more parameters of one or more of an access node - access and mobility management function (AMF) interface, or an access node - user plane function (UPF) interface, related to the UE; means for receiving a UE-related request message from an AMF that includes an update to at least one of the one or more parameters of the at least one of the access node - AMF interface or the access node - UPF interface; and means for forwarding the update to the at least one of the one or more parameters to at least one of the candidate access nodes for use by a target access node of the at least one of the candidate access nodes in connection with the handover.

2. The apparatus of claim 1, wherein the one or more parameters include one or more parameters of an access node - AMF interface related to the UE, and the UE- related request message includes an update to at least one of the one or more parameters of the access node - AMF interface, and wherein the update to the at least one of the one or more parameters is forwarded to the at least one of the candidate access nodes for use by the target access node for a path switch with the AMF.

3. The apparatus of claim 2, wherein the one or more parameters of the access node - AMF interface include an identifier of the UE over the access node - AMF interface within the AMF.

4. The apparatus of claim 2 or claim 3, wherein the means for configuring the handover includes at least means for configuring a lower-layer triggered mobility (LTM) cell switch of the UE.-53-5. The apparatus of claim 4, wherein the update to the at least one of the one or more parameters is forwarded to all of the candidate access nodes.

6. The apparatus of claim 4 or claim 5, wherein the apparatus further comprises at least means for making a decision to execute the LTM cell switch of the UE to the target access node, and the update to the at least one of the one or more parameters is forwarded only to the target access node.

7. The apparatus of any of claims 2 to 6, wherein the means for configuring the handover includes at least means for configuring a conditional handover of the UE.

8. The apparatus of claim 7, wherein the update to the at least one of the one or more parameters is forwarded to all of the candidate access nodes.

9. The apparatus of any of claims 1 to 8, wherein the one or more parameters include user plane transport layer information for the access node - UPF interface related to the UE, and the UE-related request message includes an update to the user plane transport layer information, and wherein the update to the user plane transport layer information is forwarded to the at least one of the candidate access nodes for use by the target access node for routing uplink data.

10. A method comprising: configuring a handover of a user equipment (UE) in which a handover request message is sent to candidate access nodes to prepare for the handover, the handover request message including one or more parameters of one or more of an access node - access and mobility management function (AMF) interface, or an access node - user plane function (UPF) interface, related to the UE; receiving a UE-related request message from an AMF that includes an update to at least one of the one or more parameters of the at least one of the access node - AMF interface or the access node - UPF interface; andforwarding the update to the at least one of the one or more parameters to at least one of the candidate access nodes for use by a target access node of the at least one of the candidate access nodes in connection with the handover.

11. The method of claim 10, wherein the one or more parameters include one or more parameters of an access node - AMF interface related to the UE, and the UE- related request message includes an update to at least one of the one or more parameters of the access node - AMF interface, and wherein the update to the at least one of the one or more parameters is forwarded to the at least one of the candidate access nodes for use by the target access node for a path switch with the AMF.

12. The method of claim 11, wherein the one or more parameters of the access node - AMF interface include an identifier of the UE over the access node - AMF interface within the AMF.

13. The method of claim 11 or claim 12, wherein configuring the handover of the UE includes at least configuring a lower-layer triggered mobility (LTM) cell switch of the UE.

14. The method of claim 13, wherein the update to the at least one of the one or more parameters is forwarded to all of the candidate access nodes.

15. The method of claim 13 or claim 14, wherein the method further comprises at least making a decision to execute the LTM cell switch of the UE to the target access node, and the update to the at least one of the one or more parameters is forwarded only to the target access node.

16. The method of any of claims 11 to 15, wherein configuring the handover of the UE includes at least configuring a conditional handover of the UE.

17. The method of claim 16, wherein the update to the at least one of the one or more parameters is forwarded to all of the candidate access nodes.

18. The method of any of claims 10 to 17, wherein the one or more parameters include user plane transport layer information for the access node - UPF interface related to the UE, and the UE-related request message includes an update to the user plane transport layer information, and wherein the update to the user plane transport layer information is forwarded to the at least one of the candidate access nodes for use by the target access node for routing uplink data.

19. An apparatus comprising: means for configuring a handover of an user equipment (UE) in which a handover request message is sent to candidate access nodes to prepare the candidate access nodes for the handover, the handover request message including one or more parameters of an access node - access and mobility management function (AMF) interface related to the UE; means for receiving a UE-related request message from an AMF that includes an update to at least one of the one or more parameters of the access node - AMF interface related to the UE; and means for sending a message to the AMF that indicates the handover of the UE is configured to enable the AMF to avoid the update to the at least one of the one or more parameters while the handover is configured.

20. A method comprising: receiving a handover request message from a source access node during preparation of candidate access nodes for a handover of a user equipment (UE), the handover request message including user plane transport layer information for an access node - user plane function (UPF) interface related to the UE; carrying out the handover of the UE;carrying out a path switch procedure with an access and mobility function (AMF), in connection with the handover, and during which an update to the user plane transport layer information is received from the AMF; and forwarding the update to the user plane transport layer information to one or more of the candidate access nodes for use by a target access node of the one or more candidate access nodes in connection with a subsequent handover.

21. The method of claim 20, wherein the method further comprises forwarding the update of the user plane transport layer information to the source access node as a candidate access node for the subsequent handover.

22. The method of claim 20 or claim 21, wherein carrying out the handover includes carrying out a lower-layer triggered mobility (LTM) cell switch of the UE.

23. The method of any of claims 20 to 22, wherein carrying out the handover includes carrying out a conditional handover of the UE.

24. An apparatus comprising means for performing the method of any of claims 20 to 23.

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