Conditional fast handover of a user equipment

Abstract

A method of conditional handover (CHO) comprising receiving, by a handover (HO) source node from a HO candidate node, a default radio resource control (RRC) configuration comprising default RRC information for a HO; receiving, from a user equipment (UE), a measurement report comprising information on a radio service quality in association with the HO source node and / or with at least one radio cell provided by the HO candidate node; determining, by the HO source node, to carry out the HO of the UE to the HO candidate based on the measurement report, wherein the HO is a conditional fast HO based on service delay requirements and / or service reliability; transmitting a conditional fast HO command to the UE wherein the command comprises the default RRC configuration. The conditional fast HO command may comprise a cell radio network temporary identifier (C-RNTI) selected from a pool of C-RNTIs from HO candidate nodes.

Description

TECHNOLOGICAL FIELD

[0001] The present disclosure relates generally to telecommunications and, in particular, to user equipment handover in a telecommunications system. BACKGROUND 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 comprise, 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 comprise two-way or multi-way calls, data communication or multimedia services and access to a data network system, such as the Internet.

[0002] 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 comprise 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.

[0003] 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 with other 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.

[0004] 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 (3GPP). BRIEF SUMMARY

[0005] Example implementations of the present disclosure are directed to telecommunications and, in particular, to user equipment handover in a telecommunications system. According to example implementations, a handover candidate target access node may be configured to generate a default radio resource control (RRC) configuration for a handover, and transmit the default RRC configuration to a handover source access node. The handover source access node may be configured to receive a measurement report from at least one user equipment, where the measurement report comprises information on a radio service quality in association with at least one radio cell provided by one or more handover candidate target access nodes.

[0006] The handover source access node may be configured to determine to carry out the handover of the user equipment(s) to at least one of the handover candidate target access node(s) and whether the handover is a conditional handover based on the information on the radio service quality, service delay requirements and / or service reliability requirements. The handover source access node may be configured to transmit a handover command to the user equipment(s), wherein, in the case the handover is the conditional handover, the handover command comprises a condition for carrying out the handover. And the handover candidate target access node may be configured to carry out the handover of the user equipment to a radio cell provided by the handover candidate target access node, initiated by the user equipment when the condition for carrying out the handover is satisfied by the radio cell.

[0007] The present disclosure thus comprises, without limitation, the following example implementations.

[0008] 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, by a handover source access node from one or more handover candidate target access nodes, one or more default radio resource control configurations comprising default radio resource control configuration information for a handover; receive, from at least one user equipment, a measurement report comprising information on a radio service quality in association with the handover source access node and / or with at least one radio cell provided by the one or more handover candidate target access nodes; determine, by the handover source access node, to carry out the handover of the at least one user equipment to at least one of the one or more handover candidate target access nodes based on the measurement report, and that the handover is a conditional fast handover based on service delay requirements and / or service reliability requirements; and transmit a conditional fast handover command to the at least one user equipment, wherein the conditional fast handover command comprises the default radio resource control configuration information

[0009] Some example implementations provide an apparatus comprising: means for receiving, by a handover source access node from one or more handover candidate target access nodes, one or more default radio resource control configurations comprising default radio resource control configuration information for a handover; means for receiving, from at least one user equipment, a measurement report comprising information on a radio service quality in association with the handover source access node and / or with at least one radio cell provided by the one or more handover candidate target access nodes; means for determining, by the handover source access node, to carry out the handover of the at least one user equipment to at least one of the one or more handover candidate target access nodes based on the measurement report, and that the handover is a conditional fast handover based on service delay requirements and / or service reliability requirements; and means for transmitting a conditional fast handover command to the at least one user equipment, wherein the conditional fast handover command comprises the default radio resource control configuration information

[0010] Some example implementations provide a method comprising: receiving, by a handover source access node from one or more handover candidate target access nodes, one or more default radio resource control configurations comprising default radio resource control configuration information for a handover; receiving, from at least one user equipment, a measurement report comprising information on a radio service quality in association with the handover source access node and / or with at least one radio cell provided by the one or more handover candidate target access nodes; determining, by the handover source access node, to carry out the handover of the at least one user equipment to at least one of the one or more handover candidate target access nodes based on the measurement report, and that the handover is a conditional fast handover based on service delay requirements and / or service reliability requirements; and transmitting a conditional fast handover command to the at least one user equipment, wherein the conditional fast handover command comprises the default radio resource control configuration information

[0011] 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, by a handover source access node from one or more handover candidate target access nodes, one or more default radio resource control configurations comprising default radio resource control configuration information for a handover; receive, from at least one user equipment, a measurement report comprising information on a radio service quality in association with the handover source access node and / or with at least one radio cell provided by the one or more handover candidate target access nodes; determine, by the handover source access node, to carry out the handover of the at least one user equipment to at least one of the one or more handover candidate target access nodes based on the measurement report, and that the handover is a conditional fast handover based on service delay requirements and / or service reliability requirements; and transmit a conditional fast handover command to the at least one user equipment, wherein the conditional fast handover command comprises the default radio resource control configuration information

[0012] 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: generate, by a handover candidate target access node at least one default radio resource control configuration comprising default radio resource control configuration information for a fast handover; transmit the at least one default radio resource control configuration to a handover source access node for the fast handover of at least one user equipment; receive, from the at least one user equipment, a request for the fast handover, and carry out the fast handover of the at least one user equipment to a radio cell provided by the handover candidate target access node using the default radio resource control configuration information.

[0013] Some example implementations provide an apparatus comprising: means for generating, by a handover candidate target access node at least one default radio resource control configuration comprising default radio resource control configuration information for a fast handover; means for transmitting the at least one default radio resource control configuration to a handover source access node for the fast handover of at least one user equipment; means for receiving, from the at least one user equipment, a request for the fast handover, and means for carrying out the fast handover of the at least one user equipment to a radio cell provided by the handover candidate target access node using the default radio resource control configuration information.

[0014] Some example implementations provide a method comprising: generating, by a handover candidate target access node at least one default radio resource control configuration comprising default radio resource control configuration information for a fast handover; transmitting the at least one default radio resource control configuration to a handover source access node for the fast handover of at least one user equipment; receiving, from the at least one user equipment, a request for the fast handover, and carrying out the fast handover of the at least one user equipment to a radio cell provided by the handover candidate target access node using the default radio resource control configuration information.

[0015] 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: generate, by a handover candidate target access node at least one default radio resource control configuration comprising default radio resource control configuration information for a fast handover; transmit the at least one default radio resource control configuration to a handover source access node for the fast handover of at least one user equipment; receive, from the at least one user equipment, a request for the fast handover, and carry out the fast handover of the at least one user equipment to a radio cell provided by the handover candidate target access node using the default radio resource control configuration information.

[0016] 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 comprises 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.

[0017] 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)

[0018] 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:

[0019] FIG. 1 illustrates a telecommunications system that comprises 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;

[0020] FIG 2 illustrates a deployment of a PLMN, according to some example implementations;

[0021] FIG. 3 is a signaling chart of a conventional handover procedure;

[0022] FIG. 4 is a signaling chart of a conditional handover procedure;

[0023] FIG. 5 is a signaling chart of a fast handover procedure, according to some example implementations;

[0024] FIGS. 6Aand 6B illustrate a signaling chart of a conditional fast handover procedure, according to some example implementations;

[0025] FIGS. 7A, 7B, 7C and 7D are flowcharts illustrating various steps in a method according to various example implementations;

[0026] FIGS. 8A, 8B, 8C, 8D, 8E, 8F and 8G are flowcharts illustrating various steps in a method according to various example implementations;

[0027] FIG. 9 illustrates an apparatus according to some example implementations. DETAILED DESCRIPTION

[0028] 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.

[0029] 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.

[0030] 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 comprising clients and servers; and within a network, these computers may be interconnected directly or indirectly by various means comprising via one or more switches, routers, gateways, access points or the like.

[0031] 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 3GPP technologies such as Global System for Mobile Communications (GSM), UMTS, LTE, LTE Advanced, 5G NR, 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.

[0032] 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 (comprising 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 circuits) 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.

[0033] 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.

[0034] FIG. 1 illustrates a telecommunications system 100 according to various example implementations of the present disclosure. The telecommunications system generally comprises one or more telecommunications networks. As shown, for example, the system comprises one or more public land mobile networks (PLMNs) 102 coupled to one or more other external data networks 104 - notably comprising a wide area network (WAN) such as the Internet. Each of the PLMNs comprises 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.

[0035] In addition, the system comprises 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.

[0036] 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-latency communications (URLLC), and massive machine type communications (mMTC) or massive internet of things (MIoT).

[0037] Examples of radio access technologies comprise 3GPP radio access technologies such as GSM, UMTS, LTE, LTE Advanced, 5GNR, 5G Advanced, and 6G. Other examples of radio access technologies comprise 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).

[0038] In various examples, a RAN 108 may be configured as one or more macrocells, microcells, picocells, femtocells or the like. The RAN may generally comprise 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 comprise some type of network controlling / governing entity responsible for control of the radio access nodes. The network controlling / governing entity and radio access node may be separate or integrated into a single apparatus. The network controlling / governing entity may comprise 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.

[0039] A RAN 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), optical transport network (OTN), time sensitive networking (TSN) and / or any other data link layer network, possibly comprising radio links. The RAN may be connected to a CN 106 through one or more gateways, network functions or the like.

[0040] 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 comprises 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 comprises 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 comprises 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.

[0041] 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 comprises 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 comprise 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.

[0042] In some deployments, operations of a radio access node 202 may be distributed or functionally split into components comprising one or more remote radio head (RRHs) or radio units (RUs), and a baseband unit (BBU); and in some architectures, the BBU may be split into a distributed unit (DU) and a central / centralized unit (CU), such as a server, host or node. In some architectures, the RRH / RU and DU may be collocated. It is also possible that node operations may be distributed among a plurality of servers, hosts or nodes.

[0043] It should also be understood that the distribution of work between CN 106 operations and radio access node 202 operations may vary depending on implementation. Thus, a 5G network architecture may be based on a so-called CU-DU split. One gNB-CU (central node) may control one or more gNB-DUs. The gNB-CU may control a 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 comprise, 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 comprise 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 skilled person is familiar with the OSI model and the functionalities within each layer.

[0044] In some example implementations, the server or CU 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, and the boundary where the responsibility is shifted between the CU and the DU may be selected according to implementation.

[0045] Although only one radio access node 202 is shown in FIG. 2, the deployment may comprise 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 radio access node and the CN is referred to as the NG interface, which is a network interface between the radio access node and an access and mobility management function (AMF) of the 5GC. 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, such as the NG application protocol (NGAP) for the NG interface between the radio access node and the CN.

[0046] 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 radio cells of one or more radio access nodes 202. To continuously monitor the UE’s radio link condition toward a serving radio cell provided by a serving radio access node, the UE may be configured to measure received signal level and quality from the serving radio cell as well as a list of configured neighboring radio 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 a handover (HO) of the UE from the serving radio cell provided by the serving radio access node (a handover source access node) to a new radio cell provided by a target radio access node (a target handover access node).

[0047] FIG. 3 is a signaling chart 300 of a conventional (inter-node) handover procedure involving a UE 110, a handover source access node (source node) 202A that is currently serving (connected to) the UE, and one or more handover candidate target access nodes (target nodes) 202B. As shown, the UE at step 301 may be configured, such as by an RRC reconfiguration, to report measurements of one or more neighboring radio cells, such as on an event basis. Once the event condition holds, the UE may at step 302 send (transmit) a measurement report indicating relevant measurements for one or more radio cells provided by the handover candidate target access node(s). Depending on various configurations and requirements, the measurement may be performed on any of a number of suitable objects. Based on measurements performed and reported by the UE and other UEs served by the handover source access node, the handover source access node may be configured to derive information, such as a number of actively connected UEs, number of RRC connections, number of physical resource blocks (PRBs) in use, the transport network load (TNL) capacity, or the like.

[0048] The handover source access node 202A may at step 303 decide to initiate the handover procedure, and initiate a handover preparation in which the handover source access node at step 304 sends (transmits) a handover request message with a current configuration of the UE 110 towards the handover candidate target access node 202B controlling a target radio cell. In some cases, the handover request message may be sent over an Xn interface between the handover source access node and the handover candidate target access node, such as according to a procedure referred to as Xn handover. In some possible cases where there is no Xn interface between these two nodes, the handover candidate target access node may be accessed over AMF, such as according to a procedure referred to as NGAP handover.

[0049] The handover candidate target access node 202B may at step 305 perform admission control, such as to accept or reject the handover request, and at step 306 provide a handover request acknowledgement (ACK) message comprising a configuration of initial access resources for the UE 110 in case of acceptance. This configuration may comprise, for example, a cell radio network temporary identifier (C-RNTI), a contention-free random access (CFRA) preamble, a data radio bearer (DRB) configuration, quality of service (QoS) flow to DRB mapping, UE capability related features enabled by the handover candidate target access node, or the like. The handover source access node 202A may then at step 307 send (transmit) a handover command message that comprises the configuration for the target radio cell towards the UE.

[0050] Upon receipt of the handover command from the handover source node 202A, the UE 110 may at steps 308, 309, 310 obtain downlink (DL) and uplink (UL) synchronization with the handover candidate target access node 202B, and thereafter complete the handover procedure. As shown, in some examples, the handover command may be provided at step 307 by a RRC reconfiguration; and in some of these examples, the handover procedure may comprise a random access procedure for handover, comprising downlink (DL) and uplink (UL) synchronization and random access channel (RACH) access to the handover candidate target access node, and random access response (RAR) message from the handover candidate target access node. The UE may then send (transmit) a RRC reconfiguration complete message to the handover candidate target access node to complete the handover procedure.

[0051] A possible issue with the message sequence flow of the (conventional) handover procedure may be that the handover preparation may take a lot of time and multiple signaling exchanges to request the resource reservation at the handover candidate target access node 202B and to receive the handover request ACK with the target radio cell configuration, thereby likely causing delay (or even leading to failure) during the overall handover procedure. The delay may vary depending on the deployment (e.g., NGAP handover or Xn handover) or the architecture (e.g., disaggregated or monolithic structure). In some possible cases, delays up to 60 milliseconds may be expected for example in a disaggregated scenario with NGAP handover. This delay may in turn increase the likelihood of possible handover failure (HOF) and / or radio link failure (RLF).

[0052] The 3 GPP has introduced a so-call conditional handover (CHO) procedure, which may be considered a potential candidate for addressing some of the issues of the convention handover procedure.

[0053] Broadly speaking, in the case of CHO, a UE 110 may be configured with a CHO command containing the target radio cell configuration and one or more CHO conditions for carrying out the handover to one or more radio 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 radio cell falls below a threshold RSRP Each of the target radio cell(s) / handover candidate target access node(s) 202B 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 target radio cell, UE may be configured to apply the CHO command and use the reserved CFRA resources to initiate the random access procedure to the target radio cell. In some examples, the UE may be configured with multiple conditions for multiple target radio cells.

[0054] 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 radio cell / handover source node 202A to trigger the HO execution (as shown at step 307 of FIG. 3 for a conventional HO) after the measurement report (as shown at steps 302 of FIG. 3).

[0055] FIG. 4 is a signaling chart 400 of a CHO procedure involving a UE 110, a handover source access node (source node) 202A that is currently serving (connected to) the UE, and one or more handover candidate target access nodes (target nodes) 202B (two handover candidate target access nodes shown). Similar to the conventional HO procedure, the UE at step 401 may be configured to report measurements of one or more neighboring radio cells, and at step 402 send (transmit) a measurement report indicating relevant measurements for one or more target radio cells provided by the handover candidate target access node(s).

[0056] The handover source access node 202A 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 handover source access node at step 404 sends (transmits) a handover request message with a current configuration of the UE 110 towards each of the handover candidate target access node(s) 202B.

[0057] Each handover candidate target access node 202B may at step 405 perform admission control, such as to accept or reject the handover request, and at step 406 provide a handover request ACK message comprising a configuration of initial access resources for the UE 110. This configuration may be the same as or similar to the conventional HO procedure, comprising for example, a C-RNTI, a CFRA preamble, a DRB configuration, QoS flow to DRB mapping, UE capability related features enabled by the handover candidate target access node, or the like.

[0058] The handover source access node 202A may then at step 407 send (transmit) a CHO command message that comprises the configuration for the target radio cell towards the UE. The CHO command message may be sent similar to the HO command message, such as by a RRC reconfiguration. The CHO command message also comprises one or more CHO conditions for one or more target radio cells of the handover candidate target access node(s) 202B.

[0059] Upon receipt of the handover command from the handover source node 202A, when the CHO command message is sent by a RRC reconfiguration, the UE 110 may at step 408 send (transmit) a RRC reconfiguration complete message to the handover source node. The UE maintains its connection with the handover source node, and at step 409 starts evaluating the CHO condition(s) for the target radio cell(s). If at least one target radio cell satisfies a corresponding CHO condition, the UE may at steps 410, 411, 412 obtain DL and UL synchronization and RACH access with the handover candidate target access node 202B that provides the target radio cell, and thereafter complete the handover procedure, such as in a manner similar to steps 308, 309, 310 described above for the conventional HO procedure.

[0060] Relative to the conventional HO, CHO may reduce the HOF and REF rate as target radio cell(s) of the handover candidate target access node(s) 202B may be prepared earlier, and the UE 110 may start HO execution as soon as a CHO condition is met. In CHO, however, decoupling handover preparation and execution may lead to unnecessary handover preparation with inefficient dedicated resources at the network. Also as CHO configuration is prepared earlier, there may be more time from preparation to execution with higher probability of a change in the handover source node 202A configuration, which may lead to a mismatch at execution time.

[0061] Example implementations of the present disclosure therefore provide solutions that support (enhanced and fast) mobility use cases, such as (mter-node) handover or the like, particularly in an efficient, flexible yet reliable manner. Some example implementations provide fast handover (FHO) and conventional FHO (CFHO) procedures that employ a baseline RRC configuration (at times referred to as a default RRC configuration) to save time spent on preparing a target radio cell, and thereby initiate the HO / CHO faster as compared to conventional HO / CHO.

[0062] FIG. 5 is a signaling chart 500 of a fast handover (FHO) procedure, according to some example implementations. As shown, at least one handover candidate target access node 202B may at step 501 generate and share a baseline RRC configuration (a default RRC configuration) for the FHO with the handover source node 202A, without a previous handover request from the handover source node (e.g., a handover request message shown at in step 304 of FIG. 3). The baseline RRC configuration may be sent (transmitted) to the handover source node in a RAN node configuration update message, or any other suitable (existing or new) message. The handover source node may at step 502 send (transmit) a corresponding acknowledgment message (e.g., RAN node configuration update ACK) back to the handover candidate target access node. In some examples, the baseline RRC configuration may be generally considered specific to a cell pair (or in other words, handover source node and target radio cell-specific).

[0063] The baseline RRC configuration generated by the handover candidate target access node 202B may comprise baseline configuration information (at times referred to as default configuration information). Depending on various implementations and / or requirements, the baseline configuration information may comprise baseline low layer configuration information, that is, configuration information for lower layer(s), such as layer 1 / LI (e.g., PHY layer), layer 2 / L2 (e g., MAC layer, RLC layer, or PDCP layer), or the like. In some more particular examples, the baseline low layer configuration information may comprise suitable LI / 2 (e.g., cell-specific) configurations, and possibly also configurations related to LI measurement.

[0064] In some examples, the baseline configuration information may comprise multiple lower layer configurations (possibly for different use cases / scenarios) as part of the baseline configuration information. One example of multiple low layer configurations may comprise configuration information (e.g., PDCP and / or RLC configurations) of a radio bearer that is specific to a network slice identifier (ID) and / or QoS parameters associated with the bearer. In some examples, then, the handover candidate target access node 202B (e.g., a target DU) may be configured to provide a lower layer configuration usable only for DRBs associated with a URLLC packet data unit (PDU) session or which generally requires high reliability. This baseline configuration may as well comprise other suitable (low layer related) configuration.

[0065] In some examples, the baseline configuration information may also comprise baseline high layer configuration information, that is, a configuration for higher layer(s), such as layer 3 / L3 or even above (e.g., RRC layer, non-access stratum (NAS) layer). The baseline high layer configuration information may also comprise measurement-related configurations for higher layers (in contrast to LI measurement configurations).

[0066] In some examples, the baseline high layer configuration information may comprise some or all of the L2 sub-layers, such as the service data adaptation protocol (SDAP) layer (e.g., for signaling radio bearers - SRBs), instead of low lower configuration information. In some examples, the baseline low layer configuration information and baseline high layer configuration information may be collectively referred to as baseline configuration information for a target radio cell of handover candidate target access node 202B.

[0067] In addition to the baseline configuration information, the baseline RRC configuration may comprise at least one criterion (e.g., a set of various criteria) that generally governs the decision as to whether to use, initiate, execute or carry out the FHO procedure with the respective handover candidate target access node 202B (target radio cell). One example of a suitable criterion indicates that a UE 110 must not use a guaranteed bit rate (GBR) configuration that cannot be supported by the target radio cell provided by the handover candidate target access node.

[0068] Other examples relating to radio (related) configurations for the UE 110 that may be supported or not supported by the handover candidate target access node 202B (target radio cell) comprise a bandwidth configuration used by the UE, certain higher layer configuration (e.g., RLC, PDCP related configuration) regarding robust header compression (ROHC), or the like. In other words, if the UE is configured with a GBR that cannot be supported by the target radio cell provided by the handover candidate target access node 202B, the criterion may indicate that FHO procedure should not be used or initiated (by the handover source node 202A) for the UE.

[0069] As another example, a criterion that may govern the decision regarding the FHO may be that the (current) load of the target radio cell provided by the handover candidate target access node 202B is lower than a predetermined or predefined load criterion (e.g., a threshold, such as 50%, 30%, or the like). In some further examples, this load criterion or threshold may be determined by the target radio cell or handover candidate target access node itself, or by any other suitable network entity / element (e.g., operations, administration and maintenance (0AM)) of the telecommunications system. The (current) load information of the target radio cell may be (recently) reported by the handover candidate target access node (e.g., periodically or on request of the handover source node 202A) or estimated by the handover source node (e.g., based on an early report from the target radio cell). The load information (and correspondingly also the load criterion / threshold) may be indicated in terms of any suitable parameter, which may comprise (but is not limited to), the number of RRC connections maintained by the handover candidate target access node, the number of active UEs served by the handover candidate target access node, the number of PRBs in use in the handover candidate target access node, the TNL capacity of the handover candidate target access node, or the like.

[0070] In examples, the baseline RRC configuration may yet further comprise a pool (list) of one or more random access preambles (at times referred to as RACK preambles) that can be used for the FHO procedure. The pool of RACH preambles may be predetermined, preconfigured or (pre-)reserved at the handover candidate target access node 202B. Any one of the preambles selected (by the handover source node 202A) from this pool and assigned to the UE 110 may be later recognizable by the handover candidate target access node during the subsequent synchronization / random access process.

[0071] Similarly, in some examples, the baseline RRC configuration may comprise a pool (list) of one or more C-RNTIs that can be used / controlled (to assign to the UE 110) by the handover source node 202A node in case of handover to a radio cell provided by the handover candidate target access node 202B. The pool of C-RNTIs may also be predetermined, preconfigured or (pre-)reserved at the handover candidate target access node. Any one of the preambles may be selected (by the handover source node) from this pool and assigned to the UE may be later readily recognizable by the handover candidate target access node during any suitable subsequent process.

[0072] In some examples, the handover candidate target access node 202B may at step 503 determine a change in the RRC configuration. In particular, for example, either or both of the pool or RACH preambles or the pool of C-RNTIs may be updated, such as after some of the RACH preambles and / or C-RNTIs have been used / occupied, reconfigured, freed, or the like. In these examples, the handover candidate target access node may generate an updated baseline RRC configuration according to the change, and at step 503-1 share the updated baseline RRC configuration with the handover source node 202A.

[0073] As suggested above, the handover source node 202A may control determination or selection of the RACH preamble and / or C-RNTI from the respective pools, such as to avoid a possible collision of the RACH preamble and / or C-RNTI. In other examples, however, the handover candidate target access node 202B may be configured to determine or select (e.g., reserve) one RACH preamble and / or C-RNTI for the UE 110.

[0074] In some possible implementations, the handover candidate target access node 202B may provide more than one target radio cell. As a result, in some examples, the handover candidate target access node may be configured to generate baseline RRC configurations for respective ones of its target radio cells. These baseline RRC configurations may be transmitted (sent) to the handover source node 202A as separate suitable messages, or as a single (e.g., aggregated or the like) suitable message. On the other hand, other handover source nodes in the telecommunications system may receive different baseline RRC configurations from the associated handover candidate target access node. In this sense, it may be considered that the baseline RRC configuration is pair-specific to the handover source node and handover candidate target access node.

[0075] Returning to FIG. 5, similar to the conventional HO procedure, the UE 110 at step 504 may be configured to report measurements of one or more neighboring radio cells, and at step 505 send (transmit) a measurement report indicating relevant measurements for one or more target radio cells provided by the handover candidate target access node(s).

[0076] Based on the measurements reported from the UE 110, the handover source node 202A may at step 506 decide to perform a handover to a cell reported by the UE that has suitable measurement results (similar to step 303 in FIG. 3). According to some example implementations of the present disclosure, the handover source node 202A may at step 507 determine whether the UE and / or the target radio cell(s) reported by the UE satisfy the at least one criterion obtained from the handover candidate target access node at step 501 (or step 503-1). The message / signaling exchanges between the handover source node and the handover candidate target access node for handover preparation in the conventional HO may be skipped, thereby improving latency and overall handover efficiency.

[0077] It may also be considered that, in example implementations of the present disclosure, the handover source node 202A (instead of the handover candidate target access node 202B in the conventional HO) may be responsible for admission control related processes. Depending on the at least one criterion for FHO obtained from the handover candidate target access node, in some examples, the handover source node may check whether the UE 110 uses a GBR configuration (or other suitable radio configuration of the UE) that cannot be supported by the target radio cell, whether the current load of the handover candidate target access node is below the (predetermined) criterion / threshold (e.g., 50%), or the like.

[0078] When it is determined the at least one criterion for FHO is met, the handover source node 202A may at step 508-1 send (transmit) a FHO command message with a UE-related configuration to the UE 110. The UE-related configuration may comprise (part or all of) the baseline configuration information of the baseline RRC configuration obtained from the handover candidate target access node 202B at step 501 (or step 503-1). In some examples, the UE-related configuration may also comprise a RACH preamble and C-RNTI selected from respective ones of the pool of RACH preambles and the pool of C-RNTIs by the handover source node.

[0079] The UE-related configuration may further comprise any other suitable configuration / information necessary for the UE 110 to be successfully handed over and connected to the handover candidate target access node 202B (target radio cell). In some examples, the UE-related configuration may comprise a user plane configuration (e.g., DRBs and SDAP, PDCP, RLC configuration). In some further examples, the UE-related configuration may also comprise a new key to be used by the handover candidate target access node for security-related procedure(s). In some examples, the UE may be configured to derive the new key from a current key and target radio cell ID.

[0080] Before, after or as the FHO command message is sent to the UE 110, the handover source node 202A may at step 508-2 also send (transmit) the UE-related configuration to the handover candidate target access node 202B (target radio cell). The UE-related configuration sent to the handover candidate target access node may comprise information similar to or the same as that sent to the UE, which may comprise the RACK preamble and C-RNTI selected from the respective pools by the handover source node. The handover information may also comprise UE context information. In some examples, the handover candidate target access node may also be notified about the user plane configuration (e.g., DRB related configuration) of the UE at the handover source node. This handover information may be prepared / generated by the handover source node and transmitted (sent) to the target radio cell in a suitable (existing or newly introduced) message or as separate messages.

[0081] Upon receipt of the FHO command message, the UE 110 may be configured to obtain DL and UL synchronization and perform random access to be successfully connected to the target radio cell provided by the handover candidate target access node 202B. This may comprise the UE at step 509 obtaining DL and UL synchronization and RACK access to the target radio cell. In the RACH access, the UE may apply the RACH preamble and C-RNTI selected from the respective pools by the handover source node 202A, and received by the UE at step 508-1.

[0082] Notably, as the FHO command and handover information messages towards the UE 110 and the handover candidate target access node 202B (target radio cell) as shown at respectively steps 508-1 and 508-2 may be sent (transmitted) in any sequence or in parallel, it is possible that, in some cases, step 509 may take place before step 508-2 (or before the complete handover information is fully updated at the handover candidate target access node side).

[0083] In some examples, then, upon receipt of the RACH preamble at step 509, the handover candidate target access node 202B (target radio cell) may identify that the UE 110 is undergoing the FHO procedure, such as based on the RACH preamble and / or C-RNTI from the respective pools of (preconfigured / reserved) RACH preambles and C-RNTIs. The handover candidate target access node may start a timer (e.g., ra-ResponseWindow) that defines a response window for the RAR message. The handover candidate target access node may at step 510 determine the handover candidate target access node will not receive the handover information from the handover source node 202A in due time to provide the RAR before expiration of the timer. In response, the handover candidate target access node may at steps 510-1 and 510-B fetch the handover information, comprising the UE context information, from the handover source node.

[0084] The handover candidate target access node 202B (target radio cell) may generate any remaining configuration based on the UE-related configuration received at step 508-2 or at step 510-2. The handover candidate target access node may at step 511 provide this remaining configuration in a RAR message to the UE 110. The UE may then at step 512 send (transmit) a RRC reconfiguration complete message to the handover candidate target access node to complete the handover procedure.

[0085] FIGS. 6A and 6B illustrate a signaling chart 600 of a conditional FHO (CFHO) procedure, according to some example implementations. As shown, the CFHO procedure involves one or more handover candidate target access nodes (target nodes) 202B that provide one or more (N) target radio cells. Similar to the FHO procedure, in the CFHO procedure, at least one handover candidate target access node 202B may at step 601 generate a baseline RRC configuration for the FHO with the handover source node 202A. The handover candidate target access node(s) may then send (transmit) the baseline RRC configuration to the handover source node, such as in a RAN node configuration update message, or any other suitable (existing or new) message. The handover source node may at step 602 send (transmit) a corresponding acknowledgment message (e.g., RAN node configuration update ACK) back to the handover candidate target access node(s).

[0086] In examples in which a handover candidate target access node 202B provides resources in multiple target radio cells, the baseline RRC configuration may comprise a basic configuration for the multiple target radio cells. In some further examples, the baseline RRC configuration may be divided into two parts to reduce its size and thereby load requirements. In this regard, the baseline RRC configuration may comprise a common node-specific part that applies across the multiple target radio cells provided by the handover candidate target access node. This part may be provided once as a reference configuration. The second part of the baseline RRC configuration be a cell-specific part, that is as cell-specific configuration for each of the multiple target radio cells on top of the reference configuration. The cell-specific part for each target radio cell may comprise, for example, a number of supported multiple-input and multiple-output (MIMO) layers, frequency, beams or the like. In these examples, both parts of the baseline RRC configuration may be provided to the handover source node 202A in a single message (e.g., RAN node configuration update message). In other examples, parts of the baseline RRC configuration may be provided in separate messages, such as one message for the common node-specific part, and one message for the node-specific part for each of the target radio cells.

[0087] Similar to the FHO procedure, in some examples, the handover candidate target access node(s) 202B may at step 603 determine a change in the RRC configuration. In these examples, the handover candidate target access node(s) may generate an updated baseline RRC configuration according to the change, and at step 603-1 share the updated baseline RRC configuration with the handover source node 202A. Also similar to the FHO procedure, the UE 110 at step 604 may be configured to report measurements of one or more neighboring radio cells, and at step 605 send (transmit) a measurement report indicating relevant measurements for one or more target radio cells provided by the handover candidate target access node(s) 202B.

[0088] Based on the measurements reported from the UE 110, the handover source access node 202A may at step 606 decide to initiate a handover procedure as a CFHO procedure. In this regard, the handover source node may make a determination to apply a conventional HO procedure or CHO procedure, such as based on the measurement report and radio service quality. Likewise, the handover source node may make a determination to apply a CHO procedure or CFHO procedure, such as based on one or more service reliability requirements (e.g., QoS on reliability), one or more service delay requirements (e.g., expected QoS on delay), or the like.

[0089] In some examples, the handover decision may be based on criteria including the radio link conditions observed by the UE 110 for the handover source access node 202A and the handover candidate target access node(s) 202B, so that the UE is served by the cell with the best radio link condition. Additionally or alternatively, the handover decision may also be based on network load balancing. In particular, for example, a handover may be triggered due to load balancing, as long as another cell can provide an acceptable radio link condition.

[0090] In some examples, the handover source access node 202A may determine to initiate a conventional HO / CHO procedure where target radio cell(s) are fully prepared, or initiate a FHO / CFHO procedure without preparation and admission control at the target radio cell(s). The handover source access node may determine to initiate a FHO procedure when the current QoS flow requires low delay, such as a low packet delay budget (PDB). The handover source access node may determine to initiate a FHO procedure when the UE HO is experiencing high mobility (and the UE’s radio link condition is quickly changing) to reduce the risk of failure before a convention HO could be initiated. The handover source access node may determine to initiate a conventional CHO procedure (with early target radio cell preparation) when the current QoS flow requires high reliability. When the current QoS flow requires high reliability, but there is limited capacity to reserve resources at the target radio cell(s) s, the handover source access node may determine to initiate a. CFHO procedure (without early target radio cell preparation). In examples in which the determination is to initiate FHO / CFHO, the handover source access node may determine capaci ty of the handover candidate target access node(s) 2028, and thereby the possibility of the handover candidate target access node(s) accepting the UE to handover without early target radio cell preparation.

[0091] The handover source access node 202A may at step 607 determine one or more CHO conditions for one or more target radio cells of the handover candidate target access node(s) 202B. The CHO condition(s) may be based on radio measurements, such as measured RSRP. The CHO condition(s) may be the same or different for each target radio cell. In some examples, the CHO condition(s) may comprise a different threshold RSRP for one or more target radio cells based on a different priority of the target radio cell(s). In some of these examples, the priority may depend on the target radio cell’s capacity (e.g., in GBR). In some examples, the handover source access node may determine CHO condition(s) for multiple target radio cells that support all or a subset of the features supported by the UE 110, and allow the UE to down select the target radio cell(s) based on active feature(s) needed for the UE’s current operation.

[0092] The handover source node 202A may at step 608-1 send (transmit) a CFHO command message (e.g., RRC reconfiguration) with the CHO condition(s) and a UE-related configuration to the UE 110. Similar to the FHO procedure, the UE-related configuration in the CFHO procedure may comprise (part or all of) the baseline configuration information of the baseline RRC configuration obtained from the handover candidate target access node(s) 202B at step 601 (or step 603-1). The UE-related configuration may also comprise a RACH preamble and C-RNTI selected from respective ones of the pool of RACH preambles and the pool of C-RNHs by the handover source node.

[0093] Before, after or as the handover command message is sent to the UE 110, the handover source node 202A may at step 608-2 also send (transmit) the UE-related configuration to the handover candidate target access node(s) 202B (target radio cell(s)), similar to step 508-1 in the FHO procedure. Again, the UE-related configuration sent (transmitted) to the handover candidate target access node(s) may comprise information similar to or the same as that sent to the UE, which may comprise the RACH preamble and C-RNTI selected from the respective pools by the handover source node. The handover information may also comprise UE context information and the user plane configuration (e.g., DRB related configuration) of the UE at the handover source node.

[0094] Upon receipt of the CFHO command message, when the CFHO command message is sent by a RRC reconfiguration, the UE 110 at step 609 may send (transmit) a RRC reconfiguration complete message to the handover source node. As shown in FIG. 6B, the UE 110 maintains its connection with the handover source node, and at step 610 starts evaluating the CHO condition(s) for the target radio cell(s) provided by the handover candidate target access node(s) 202B. During this time, in some examples, the handover source node 202A may at step 611 determine a change in the UE-related configuration sent to the handover candidate target access node 202B (target radio cell(s)). In these examples, the handover source node may at step 611-1 send (transmit) an updated UE-related configuration to the handover candidate target access node 202B.

[0095] If at least one target radio cell satisfies a corresponding CHO condition, the UE 110 may be configured to obtain DL and UL synchronization and perform random access to be successfully connected to the target radio cell provided by the handover candidate target access node 202B, similar to the FHO procedure. In this regard, the UE may at step 612 obtain DL and UL synchronization and RACH access to the target radio cell. In the RACH access, the UE may apply the RACH preamble and C-RNTI selected from the respective pools by the handover source node 202A, and received by the UE at step 608-1.

[0096] Similar to the FHO procedure, in some examples in which step 612 takes place before step 608-2 (and thereby also step 611-1), upon receipt of the RACK preamble at step 612, the handover candidate target access node 202B (target radio cell) may identify that a UE 110 is undergoing the CFHO procedure (e g., based on the RACH preamble, C-RNTI). The handover candidate target access node may start a timer (e.g., ra-ResponseWindowY and at step 613 determine the handover candidate target access node will not receive the handover information from the handover source node 202A in due time to provide the RAR before expiration of the timer. In response, the handover candidate target access node may at steps 613-1 and 613-2 fetch the handover information, comprising the UE context information, from the handover source node.

[0097] The handover candidate target access node 202B (target radio cell) may generate any remaining configuration based on the UE-related configuration received at step 608-2 / 611-1 or at step 613-2. The handover candidate target access node may at step 614 provide this remaining configuration in a RAR message to the UE 110. The UE may then at step 615 send (transmit) a RRC reconfiguration complete message to the handover candidate target access node to complete the handover procedure.

[0098] In some examples of CHFO failure, the UE 110 may be configured to initiate a re-establishment according to a connection re-establishment procedure. In this regard, the UE may attempt re-establishment of an RRC connection at one of the candidate target cells for which the UE received a UE-related configuration in the CFHO command message at step 608-1. Similar to CHO failure, the UE may therefore benefit from the preparation at the target radio cell with which the UE attempts to re-establish a connection.

[0099] FIGS. 7A~ 7D are flowcharts illustrating various steps in a method 700 according to various example implementations. The method comprises receiving, by a handover source access node from one or more handover candidate target access nodes, one or more default radio resource control configurations comprising default radio resource control configuration information for a handover, as shown at block 702 of FIG. 7A. The method comprises receiving, from at least one user equipment, a measurement report comprising information on a radio service quality in association with the handover source access node and / or with at least one radio cell provided by the one or more handover candidate target access nodes, as shown at block 704. The method comprises determining, by the handover source access node, to carry out the handover of the at least one user equipment to at least one of the one or more handover candidate target access nodes based on the measurement report, and that the handover is a conditional fast handover based on service delay requirements and / or service reliability requirements, as shown at block 706. And the method comprises transmitting a conditional fast handover command to the at least one user equipment, wherein the conditional fast handover command comprises the default radio resource control configuration information, as shown at block 708.

[0100] In some examples, receiving the one or more default radio resource control configurations at block 702 comprises receiving, from the one or more handover candidate target access nodes, one or more radio access node configuration update messages comprising the one or more default radio resource control configurations, as shwon at block 71.0 of FIG. 7B. In some of these examples, receiving the one or more default radio resource control configurations also comprises transmitting, to the one or more handover candidate target access nodes, one or more radio access node configuration update acknowledge messages in response to the one or more radio access node configuration update messages, as shown at block 712.

[0101] In some examples, the one or more default radio resource control configurations comprise information on at least one radio cell provided by the least one of the one or more handover candidate target access nodes, a pool of random access preambles and a pool of cell radio network temporary identifiers (C-RNTIs).

[0102] In some examples, the conditional fast handover command transmitted to the at least one user equipment at block 708 comprises the one or more default radio resource control configurations, at least one selected random access preamble from the pool of random access preambles, and at least one selected C-RNTI from the pool of C-RNTIs from each selected handover candidate target access node.

[0103] In some examples, the conditional fast handover command transmitted to the at least one user equipment at block 708 further identifies the one or more handover candidate target access nodes, and comprises the default radio resource control configuration information for the one or more handover candidate target access nodes.

[0104] In some examples, the method 700 further comprises determining a condition for carrying out the conditional fast handover of the at least one user equipment to at least one of the one or more handover candidate target access nodes, as shown at block 714 of FIG. 7C. In some of these examples, the conditional fast handover command transmitted to the at least one user equipment at block 708 further comprises the condition.

[0105] In some examples, the method 700 further comprises transmitting, to the one or more handover candidate target access nodes, handover information in association with the at least one user equipment, the handover information comprising at least one selected random access preamble, at least one selected cell radio network temporary identifier (C-RNTI), and user equipment context information, as shown at block 716 of FIG. 7D.

[0106] FIGS. 8A 8G are flowcharts illustrating various steps in a method 800 according to various example implementations. The method comprises generating, by a handover candidate target access node, at least one default radio resource control configuration comprising default radio resource control configuration information for a fast handover, as shown at block 802 of FIG. 8A. The method comprises transmitting the at least one default radio resource control configuration to a handover source access node for the fast handover of at. least one user equipment, as shown at block 804.The method comprises receiving, from the at least one user equipment, a request for the fast handover, as shown at block 806. And the method comprises carrying out the fast handover of the at least one user equipment to a radio cell provided by the handover candidate target access node using the default radio resource control configuration information, as shown at block 808.

[0107] In some examples, the handover candidate target access node provides a plurality' of radio cells. In some of these examples, generating the at least one default radio resource control configuration at block 802 comprises for each radio resource control configuraiotn, generating a common part of the default radio resource control configuration that applies to the plurality' of radio cells, as shown at block 810 of FIG. 8B. Generating the default radio resource control configuration m these examples also comprises generating cell-sped fit: parts of the default radio resource control configuration that apply to respective ones of the plura lity of radio cells, as shown at block 812,

[0108] In some examples, transmitting the at least one default radio resource control configuration at block 804 comprises transmitting a radio access node configuration update messages comprising the at least one default radio resource control configuration, as shown at block 814 of FIG. 8C. Transmitting the default radio resource control configuration in these examples also comprises receiving, from the handover source access node, a radio access node configuration update acknowledge message in response to the radio access node configuration update message, as shown at block 816.

[0109] In some examples, the method 800 further comprises determining, by the handover candidate target access node, a, change in the at least one default radio resource control configuration, as shown at block 818 of FIG. 8D. In some of these examples, the mehtod also comprises generating, by the handover candidate target access node, at least, one updated default radio resource control configuration based on the change, and transmitting the at least one updated default radio resource control configuration to the handover source access node, as shown at blocks 820 and 822.

[0110] In some examples, the at least one default radio resource control configuration comprises information on at least one radio cell provided by the handover candidate target access node, a pool of random access preambles, and a pool of cell radio network temporary' identifiers (C-RNTIs).

[0111] in some examples, the method 800 further comprises receiving, from the handover source access node, handover information in association with the at least one user equipment, the handover information comprising at least one selected random access preamble, at least one selected C-RNTI, and user equipment context information, as shown at block 824 of FIG. 8E.

[0112] In some examples, the request for the fast handover received from the at least one user equipment comprises the at least one selected random access preamble and the at least one selected C-RNTI. [Oil3] In some examples, the method 800 further comprises generating a full configuration for the at least one user equipment based on the at least one default radio resource control configuration, and the handover information received from the handover source access node, as shown at block 826 of FIG. 8F. In some of these examples, carrying out the handover at block 808 comprises transmitting the full configuration to the at least one user equipment, as shown at block 828,

[0114] In some examples, the request for the fast handover received from the at least one user equipment comprises at least one selected random access preamble and at least one selected C-RNTI. In some of these examples, carrying out the handover at block 808 also comprises obtaining, from the handover source access node, user equipment context information in association with the at least one user equipment, as shown at block 830 of FIG RG H Lv.B< OVJ.

[0115] 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, handover source access node 202A and / or handover candidate target access node 202B, may be implemented by various means. Means for implementing the system and its components may comprise 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.

[0116] According to some example implementations, at least some of the method 700 described with respect to FIGS. 7A-7D may be carried out by an apparatus comprising means for performing functions corresponding steps of the method. Similarly, at least some of the method 800 described with respect to FIGS. 8A-8G may be carried out by an apparatus comprising means for performing functions corresponding steps of the method. Examples of a suitable apparatus may comprise a gNB (e.g., gNB-DU, gNB-CU), ng~ eNB or any suitable apparatus, such as a server, host or node.

[0117] FIG. 9 illustrates an apparatus 900 in which means for performing various functions comprises 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 comprise one or more of each of a number of components such as, for example, processing circuitry 902 connected to computer-readable storage medium or other memory 904.

[0118] The processing circuitry 902 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 904 (of the same or another apparatus).

[0119] The processing circuitry 902 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 comprise 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 processing circuitry may be appropriately programmed to perform functions or operations according to example implementations of the present disclosure.

[0120] The memory 904 is generally any piece of computer hardware that is capable of storing information such as, for example, data, computer programs, instructions 906 (e.g., computer-readable program code) and / or other suitable information either on a temporary’ basis and / or a permanent basis. The memory may comprise volatile and / or non-volatile memoty, and may be fixed or removable. Examples of suitable memory comprise 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.

[0121] The memory 904 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, software distribution packages, 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.

[0122] In addition to the memory 904 (e.g., computer-readable storage medium), the processing circuitry 902 may also be connected to one or more interfaces for displaying, transmitting and / or receiving information. The interfaces may comprise a communications interface 908 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 comprise a network interface controller (NIC), wireless NIC (WNIC) or the like.

[0123] Execution of the instructions 906 by the processing circuitry 902, or storage of the instructions in the memory 904, supports combinations of operations for implementing example implementations of the present disclosure. In this manner, an apparatus 900 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.

[0124] Some example implementations of the present disclosure may also be earned 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 disclosure is well within the scope of a person of ordinary skill in the art,

[0125] 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 of manufacture, 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.

[0126] Retrieval, loading and execution of instructions comprising 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.

[0127] As explained above and reiterated below, the present disclosure comprises, without limitation, the following example implementations.

[0128] 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: receive, by a handover source access node from one or more handover candidate target access nodes, one or more default radio resource control configurations comprising default radio resource control configuration information for a handover; receive, from at least, one user equipment, a measurement report comprising information on a radio service quality in association with the handover source access node and / or with at least one radio cell provided by the one or more handover candidate target access nodes; determine, by the handover source access node, to carry out the handover of the at least one user equipment to at least one of the one or more handover candidate target access nodes based on the measurement report, and that the handover is a conditional fast handover based on service delay requirements and / or service reliability requirements; and transmit a conditional fast handover command to the at least one user equipment, wherein the conditional fast handover command comprises the default radio resource control configuration information

[0129] Clause 2. The apparatus of clause 1, wherein the apparatus caused to receive the one or more default radio resource control configurations comprises the apparatus caused to: receive, from the one or more handover candidate target access nodes, one or more radio access node configuration update messages comprising the one or more default radio resource control configurations, and transmit, to the one or more handover candidate target access nodes, one or more radio access node configuration update acknowledge messages in response to the one or more radio access node configuration update messages.

[0130] Clause 3. The apparatus of clause 1 or clause 2, wherein the one or more default radio resource control configurations comprise information on at least one radio cell provided by the least one of the one or more handover candidate target access nodes, a pool of random access preambles, and a pool of cell radio network temporary identifiers (C-RNTIs).

[0131] Clause 4. The apparatus of clause 3, wherein the conditional fast handover command transmitted to the at least one user equipment comprises the one or more default radio resource control configurations, at least one selected random access preamble from the pool of random access preambles, and at least, one selected C-RNTI from the pool of C-RNTIs from each selected handover candidate target access node.

[0132] Clause 5. The apparatus of clause 4, wherein the conditional fast handover command transmitted to the at least one user equipment further identifies the one or more handover candidate target access nodes, and comprises the default radio resource control configuration information for the one or more handover candidate target access nodes.

[0133] Clause 6. The apparatus of any of clauses 1 to 5, wherein the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further determine a condition for carrying out the conditional fast handover of the at least one user equipment to at least one of the one or more handover candidate target access nodes, and wherein the conditional fast handover command transmitted to the at least one user equipment further comprises the condition.

[0134] Clause 7. The apparatus of any of clauses 1 to 6, wherein the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further transmit, to the one or more handover candidate target access nodes, handover information in association with the at least one user equipment, the handover information comprising at least one selected random access preamble, at least one selected cell radio network temporary identifier (C-RNTI), and user equipment context information.

[0135] Clause 8. An apparatus comprising: means for receiving, by a handover source access node from one or more handover candidate target access nodes, one or more default radio resource control configurations comprising default radio resource control configuration information for a handover; means for receiving, from at least one user equipment, a measurement report comprising information on a radio service quality' in association with the handover source access node and / or with at least one radio cell provided by the one or more handover candidate target access nodes; means for determining, by the handover source access node, to carry out the handover of the at least one user equipment to at least one of the one or more handover candidate target access nodes based on the measurement report, and that the handover is a conditional fast handover based on service delay requirements and / or service reliability requirements; and means for transmitting a conditional fast handover command to the at least one user equipment, wherein the conditional fast handover command comprises the default radio resource control configuration information

[0136] Clause 9. The apparatus of clause 8, wherein the means for receiving the one or more default radio resource control configurations comprises: means for receiving, from the one or more handover candidate target access nodes, one or more radio access node configuration update messages comprising the one or more default radio resource control configurations; and means for transmitting, to the one or more handover candidate target access nodes, one or more radio access node configuration update acknowledge messages in response to the one or more radio access node configuration update messages,

[0137] Clause 10. The apparatus of clause 8 or clause 9, wherein the one or more default radio resource control configurations comprise information on at least one radio cell provided by the least one of the one or more handover candidate target access nodes, a pool of random access preambles, and a pool of cell radio network temporary identifiers (C-RMls).

[0138] Clause 11. The apparatus of clause 10, wherein the conditional fast handover command transmitted to the at least one user equipment comprises the one or more default radio resource control configurations, at least one selected random access preamble from the pool of random access preambles, and at least one selected C-RNTI from the pool of C-RNTIs from each selected handover candidate target access node.

[0139] Clause 12. The apparatus of clause 11, wherein the conditional fast handover command transmitted to the at least one user equipment further identifies the one or more handover candidate target access nodes, and comprises the default radio resource control configuration information for the one or more handover candidate target access nodes.

[0140] Clause 13. The apparatus of any of clauses 8 to 12, wherein the apparatus further comprises means for determining a condition for carrying out the conditional fast handover of the at least one user equipment to at least one of the one or more handover candidate target access nodes, and wherein the conditional fest handover command transmitted to the at least one user equipment further comprises the condition.

[0141] Clause 14. The apparatus of any of clauses 8 to 13, wherein the apparatus further comprises means for transmitting, to the one or more handover candidate target access nodes, handover information m association with the at least one user equipment, the handover information comprising at least one selected random access preamble, at least one selected cell radio network temporary identifier (C-RNTI), and user equipment context information.

[0142] Clause 15. A method comprising: receiving, by a handover source access node from one or more handover candidate target access nodes, one or more default radio resource control configurations comprising default radio resource control configuration information for a handover; receiving, from at least one user equipment, a measurement report comprising information on a radio service quality in association with the handover source access node and / or with at least one radio cell provided by the one or more handover candidate target access nodes; determining, by the handover source access node, to carry out the hando ver of the at least one user equipment to at least one of the one or more handover candidate target access nodes based on the measurement report, and that the handover is a conditional fast handover based on sendee delay requirements and / or service reliability requirements; and transmitting a conditional fast handover command to the at least one user equipment, wherein the conditional fast handover command comprises the default radio resource control configuration information

[0143] Clause 16. The method of clause 15, wherein receiving the one or more default radio resource control configurations comprises: receiving, from the one or more handover candidate target access nodes, one or more radio access node configuration update messages comprising the one or more default radio resource control configurations; and transmitting, to the one or more handover candidate target access nodes, one or more radio access node configuration update acknowledge messages in response to the one or more radio access node configuration update messages.

[0144] Clause 17. The method of clause 15 or clause 16, wherein the one or more default radio resource control configurations comprise information on at least one radio cell provided by the least one of the one or more handover candidate target access nodes, a pool of random access preambles, and a pool of cell radio network temporary identifiers (C-RNTIs).

[0145] Clause 18. The method of clause 17, wherein the conditional fast handover command transmitted to the at least one user equipment comprises the one or more default radio resource control configurations, at least one selected random access preamble from the pool of random access preambles, and at least one selected C-RNTI from the pool of C-RNTIs from each selected handover candidate target access node.

[0146] Clause 19. The method of cla use 18, wherein the conditional fast handover command transmitted to the at least one user equipment further identifies the one or more handover candidate target access nodes, and comprises the default radio resource control configuration information for the one or more handover candidate target access nodes.

[0147] Clause 20. The method of any of clauses 15 to 19, wherein the method further comprises determining a condition for carrying out the conditional fast handover of the at least one user equipment to at least one of the one or more handover candidate target access nodes, and w herein the conditional fast handover command transmitted to the at least one user equipment further comprises the condition.

[0148] Clause 21. The method of any of clauses 15 to 20, wherein the method further comprises transmitting, to the one or more handover candidate target access nodes, handover information in association with the at least one user equipment, the handover information comprising at least one selected random access preamble, at least one selected cell radio network temporary identifier (C-RNTI), and user equipment context information.

[0149] Clause 22. A computer-readable storage medium that is non-transitory and has instructions stored therein that, m response to execution by at least one processing circuitry, causes an apparatus to at least: receive, by a handover source access node from, one or more handover candidate target access nodes, one or more default radio resource control configurations comprising default radio resource control configuration information for a handover; receive, from at least one user equipment, a measurement report, comprising information on a. radio service quality m association with the handover source access node and / or with at least, one radio cell provided by the one or more handover candidate target access nodes; determine, by the handover source access node, to cany out the handover of the at least one user equipment to at least one of the one or more handover candidate target access nodes based on the measurement, report, and that the handover is a conditional fast handover based on sendee delay requirements and / or service reliability requirements; and transmit a conditional fast handover command to the at least one user equipment, wherein the conditional fast handover command comprises the default radio resource control configuration information

[0150] Clause 23. The computer-readable storage medium of clause 22, wherein the apparatus caused to receive the one or more default radio resource control configurations comprises the apparatus caused to: receive, from the one or more handover candidate target access nodes, one or more radio access node configuration update messages comprising the one or more default radio resource control configurations; and transmit, to the one or more handover candidate target access nodes, one or more radio access node configuration update acknowledge messages in response to the one or more radio access node configuration update messages.

[0151] Clause 24. The computer-readable storage medium of clause 22 or clause 23, wherein the one or more default radio resource control configurations comprise information on at least one radio cell provided by the least one of the one or more handover candidate target access nodes, a pool of random access preambles, and a pool of cell radio network temporary identifiers (C-RNTIs).

[0152] Clause 25. The computer-readable storage medium of clause 24, wherein the conditional fast handover command transmitted to the at least one user equipment comprises the one or more default radio resource control configurations, at least one selected random access preamble from the pool of random access preambles, and at least one selected C-RNTI from the pool of C-RNTTs from each selected handover candidate target access node.

[0153] Clause 26. The computer-readable storage medium of clause 25, wherein the conditional fast handover command transmitted to the at least one user equipment further identifies the one or more handover candidate target access nodes, and comprises the default radio resource control configuration information for the one or more handover candidate target access nodes.

[0154] Clause 27. The computer-readable storage medium of any of clauses 22 to 26, 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 determine a condition for carrying out the conditional fast handover of the at least one user equipmen t to at least one of the one or more handover candidate target access nodes, and wherein the conditional fast handover command transmitted to the at least one user equipment further comprises the condition.

[0155] Clause 28. The computer-readable storage medium of any of clauses 22 to 27, 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 transmit, to the one or more handover candidate target access nodes, handover information in association with the at least one user equipment, the handover information comprising at least one selected random access preamble, at least one selected cell radio network temporary identifier (C-RNTI), and user equipment context information.

[0156] Clause 29. An apparatus comprising means for performing the method of any of clauses 15 to 21.

[0157] Clause 30. 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 15 to 21.

[0158] Clause 31. 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 15 to 21.

[0159] Clause 32. 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 15 to 21.

[0160] Clause 33. 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: generate, by a handover candidate target access node at least one default radio resource control configuration comprising default radio resource control configuration information for a fast handover; transmit the at least one default radio resource control configuration to a handover source access node for the fast handover of at least one user equipment; receive, from the at least one user equipment, a request for the fast, handover, and cany out the fast handover of the at least one user equipment to a radio cell provided by the handover candidate target access node using the default radio resource control configuration information.

[0161] Clause 34. The apparatus of clause 33, wherein the handover candidate target access node provides a plurality of radio cells, and the apparatus caused to generate the at least one default radio resource control configuration comprises, for each radio resource control configuration, the apparatus caused to: generate a common part of the default radio resource control configuration that applies to the plurality of radio cells; and generate cell-specific parts of the default radio resource control configuration that apply to respective ones of the plurality of radio cells.

[0162] Clause 35. The apparatus of clause 33 or clause 34, wherein the apparatus caused to transmit the at least one default radio resource control configuration comprises the apparatus caused to: transmit a radio access node configuration update message comprising the at least one default radio resource control configuration; and receive, from the handover source access node, a radio access node configuration update acknowledge message in response to the radio access node configuration update message.

[0163] Clause 36. The apparatus of any of clauses 33 to 35, wherein the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further at least: determine, by the handover candidate target access node, a change in the at least one default radio resource control configuration; generate, by the handover candidate target access node, at least one updated default radio resource control configuration based on the change, and transmit the at least one updated default radio resource control configuration to the handover source access node.

[0164] Clause 37. The apparatus of any of clauses 33 to 36, wherein the at least one default radio resource control configuration comprises information on at least one radio cell provided by the handover candidate target access node, a pool of random access preambles, and a pool of cell radio network temporary identifiers (C-RNTIs).

[0165] Clause 38. The apparatus of clause 37, wherein the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further receive, from the handover source access node, handover information in association with the at least one user equipment, the handover information comprising at least one selected random access preamble, at least one selected C-RNTI, and user equipment context information.

[0166] Clause 39. The apparatus of clause 38, wherein the request for the fast handover received from the at least one user equipment comprises the at least one selected random access preamble and the at least one selected C-RNTI.

[0167] Clause 40. The apparatus of any of clauses 37 to 39, wherein the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further generate a full configuration for the at least one user equipment based on the at least one default radio resource control configuration, and the handover information received from the handover source access node, and wherein the carrying out the handover comprises transmitting the full configuration to the at least one user equipment.

[0168] Clause 41. The apparatus of any of clauses 37 to 40, wherein the request for the fast handover received from the at least one user equipment comprises at least one selected random access preamble and at least one selected C-RNTI; and wherein the apparatus caused to carry out the fast handover comprises the apparatus caused to obtain, from the handover source access node, user equipment context information in association with the at least one user equipment.

[0169] Clause 42. An apparatus comprising: means for generating, by a handover candidate target access node at least one default radio resource control configuration comprising default radio resource control configuration information for a fast handover: means for transmitting the at least one default radio resource control configuration to a handover source access node for the fast handover of at least one user equipment; means for receiving, from the at least one user equipment, a request for the fast handover, and means for cai ry mg out the fast handover of the at least one user equipment to a radio cell provided by the handover candidate target access node using the default radio resource control configuration information.

[0170] Clause 43. The apparatus of clause 42, wherein the handover candidate target access node provides a plurality of radio cells, and the means for generating the at least one default radio resource control configuration comprises for each radio resource control configuration: means for generating a common part of the default radio resource control configuration that applies to the plurality of radio cells; and means for generating cellspecific parts of the default radio resource control configuration that apply to respective ones of the plurality of radio cells.

[0171] Clause 44. The apparatus of clause 42 or clause 43, wherein the means for transmitting the at least one default radio resource control configuration comprises: means for transmitting a radio access node configuration update message comprising the at least one default radio resource control configuration; and means for receiving, from the handover source access node, a radio access node configuration update acknowledge message in response to the radio access node configuration update message.

[0172] Clause 45. The apparatus of any of clauses 42 to 44, wherein the apparatus further comprises: means for determining, by the handover candidate target access node, a change in the at least one default radio resource control configuration; means for generating, by the handover candidate target access node, at least one updated default radio resource control configuration based on the change; and means for transmitting the at least one updated default radio resource control configuration to the handover source access node.

[0173] Clause 46. The apparatus of any of clauses 42 to 45, wherein the at least one default radio resource control configuration comprises information on at least one radio cell provided by the handover candidate target access node, a pool of random access preambles, and a pool of cell radio network temporary identifiers (C-RNTTs).

[0174] Clause 47 The apparatus of clause 46, wherein the apparatus further comprises means for receiving, from the handover source access node, handover information in association with the at least one user equipment, the handover information comprising at least one selected random access preamble, at least one selected C-RNTI, and user equipment context information.

[0175] Clause 48. The apparatus of clause 47, wherein the request for the fast handover received from the at least one user equipment comprises the at least one selected random access preamble and the at least one selected C-RNTI.

[0176] Clause 49. The apparatus of any of clauses 46 to 48, wherein the apparatus further comprises means for generating a full configuration for the at least one user equipment based on the at least one default radio resource control configuration, and the handover information received from the handover source access node, and wherein the means for carrying out the handover comprises means for transmitting the full configuration to the at least one user equipment.

[0177] Clause 50. The apparatus of any of clauses 46 to 49, wherein the request for the fast handover received from the at least one user equipment comprises at least one selected random access preamble and at least one selected C-RNTI; and wherein the means for carrying out the fast handover comprises means for obtaining, from the handover source access node, user equipment context information in association with the at least one user equipment.

[0178] Clause 51. A method comprising: generating, by a handover candidate target access node at least one default radio resource control configuration comprising default radio resource control configuration information for a fast handover; transmitting the at least one default radio resource control configuration to a handover source access node for the fast handover of at least one user equipment; receiving, from the at least one user equipment, a request for the fast handover, and carrying out the fast handover of the at least one user equipment to a radio cell provided by the handover candidate target access node using the default radio resource control configuration information.

[0179] Clause 52. The method of clause 51, wherein the handover candidate target access node provides a plurality of radio cells, and generating the at least one default radio resource control configuration comprises for each radio resource control configuration: generating a common part of the default radio resource control configuration that applies to the plurality of radio cells, and generating cell-specific parts of the default radio resource control configuration that apply to respective ones of the plurality of radio cells.

[0180] Clause 53. The method of clause 51 or clause 52, wherein transmitting the at least one default radio resource control configuration comprises' transmitting a radio access node configuration update message comprising the at least one default radio resource control configuration; and receiving, from the handover source access node, a radio access node configuration update acknowledge message in response to the radio access node configuration update message.

[0181] Clause 54. The method of any of clauses 51 to 53, wherein the method further comprises: determining, by the handover candidate target access node, a change in the at least one default radio resource control configuration; generating, by the handover candidate target access node, at least one updated default radio resource control configuration based on the change; and transmitting the at least one updated default radio resource control configuration to the handover source access node.

[0182] Clause 55. The method of any of clauses 51 to 54, wherein the at least one default radio resource control configuration comprises information on at least one radio cell provided by the handover candidate target access node, a pool of random access preambles, and a pool of cell radio network temporary identifiers (C-RNTIs).

[0183] Clause 56. The method of clause 55, wherein the method further comprises receiving, from the handover source access node, handover information in association with the at least one user equipment, the handover information comprising at least one selected random access preamble, at least one selected C-RNTI, and user equipment context information.

[0184] Clause 57. The method of clause 56, wherein the request for the fast handover received from the at least one user equipment comprises the at least one selected random access preamble and the at least one selected C-RNTT.

[0185] Clause 58. The method of any of clauses 55 to 57, wherein the method further comprises generating a full configuration for the at least one user equipment based on. the at least one default radio resource control configuration, and the handover information received from the handover source access node, and wherein the carrying out the handover comprises transmitting the full configuration to the at least one user equipment,

[0186] Clause 59. The method of any of clauses 55 to 58, wherein the request for the fast handover received from the at least one user equipment comprises at least one selected random access preamble and at least one selected C-RNTI, and wherein the carrying out the fast handover comprises obtaining, from the handover source access node, user equipment context information in association with the at least one user equipment.

[0187] Clause 60. 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: generate, by a handover candidate target access node at least one default radio resource control configuration comprising default radio resource control configuration information for a fast handover; transmit the at least one default radio resource control configuration to a handover source access node for the fast handover of at least one user equipment; receive, from the at least one user equipment, a request for the fast handover, and carry out the fast handover of the at least one user equipment to a radio cell provided by the handover candidate target access node using the default radio resource control configuration information.

[0188] Clause 61. The computer-readable storage medium of clause 60, wherein the handover candidate target access node provides a plurality of radio cells, and the apparatus caused to generate the at least one default radio resource control configuration comprises, for each radio resource control configuration, the apparatus caused to: generate a common part of the default radio resource control configuration that applies to the plurality of radio cells; and generate cell-specific parts of the default radio resource control configuration that apply to respective ones of the plurality of radio cells.

[0189] Clause 62. The computer-readable storage medium of clause 60 or clause 61, wherein the apparatus caused to transmit the at least one default radio resource control configuration comprises the apparatus caused to: transmit a. radio access node configuration update message comprising the at least one default radio resource control configuration, and receive, from the handover source access node, a radio access node configuration update acknowledge message in response to the radio access node configuration update message. [1)190] Clause 63. The computer-readable storage medium of any of clauses 60 to 62, 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 at least: determine, by the handover candidate target access node, a change in the at least one default radio resource control configuration; generate, by the handover candidate target access node, at least one updated default radio resource control configuration based on the change; and transmit the at least one updated default radio resource control configuration to the handover source access node.

[0191] Clause 64. The computer-readable storage medium of any of clauses 60 to 63, wherein the at least one default radio resource control configuration comprises information on at least one radio cell provided by the handover candidate target access node, a pool of random access preambles, and a pool of cell radio network temporary identifiers (C-RNTls)

[0192] Clause 65. The computer-readable storage medium of clause 64, 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 receive, from the handover source access node, handover information in association with the at least one user equipment, the handover information comprising at least one selected random access preamble, at least one selected C-RNTI, and user equipment context information.

[0193] Clause 66. The computer-readable storage medium of clause 65, wherein the request for the fast handover received from the at least one user equipment comprises the at least one selected random access preamble and the at least one selected C-RNTI.

[0194] Clause 67. The computer-readable storage medium of any of clauses 64 to 66, 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 generate a full configuration for the at least one user equipment based on the at least one default radio resource control configuration, and the handover information received from the handover source access node, and wherein the carrying out the handover comprises transmitting the full configuration to the at least one user equipment.

[0195] Clause 68. The computer-readable storage medium of any of clauses 64 to 67, wherein the request for the fast handover received from the at least one user equipment comprises at least one selected random access preamble and at least one selected C-RNTI; and wherein the apparatus caused to carry out the fast handover comprises the apparatus caused to obtain, from the handover source access node, user equipment context information in association with the at least one user equipment.

[0196] Clause 69. An apparatus comprising means for performing the method of any of clauses 51 to 59.

[0197] Clause 70. 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 51 to 59.

[0198] Clause 71. 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 51 to 59.

[0199] Clause 72. 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 51 to 59.

[0200] 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 the specific 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 5 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

1. An apparatus comprising:means for receiving, by a handover source access node from one or more handover candidate target access nodes, one or more default radio resource control configurations comprising default radio resource control configuration information for a handover;means for receiving, from at least one user equipment, a measurement report comprising information on a radio service quality in association with the handover source access node and / or with at least one radio cell provided by the one or more handover candidate target access nodes;means for determining, by the handover source access node, to carry out the handover of the at least one user equipment to at least one of the one or more handover candidate target access nodes based on the measurement report, and that the handover is a conditional fast handover based on service delay requirements and / or service reliability requirements; andmeans for transmitting a conditional fast handover command to the at least one user equipment, wherein the conditional fast handover command comprises the default radio resource control configuration information2. The apparatus of claim 1, wherein the means for receiving the one or more default radio resource control configurations comprises:means for receiving, from the one or more handover candidate target access nodes, one or more radio access node configuration update messages comprising the one or more default radio resource control configurations; andmeans for transmitting, to the one or more handover candidate target access nodes, one or more radio access node configuration update acknowledge messages in response to the one or more radio access node configuration update messages.

3. The apparatus of claim 1 or claim 2, wherein the one or more default radio resource control configurations comprise information on at least one radio cell provided by the least one of the one or more handover candidate target access nodes, a pool ofrandom access preambles, and a pool of cell radio network temporary identifiers (C-RNTIs).

4. The apparatus of claim 3, wherein the conditional fast handover command transmitted to the at least one user equipment comprises the one or more default radio resource control configurations, at least one selected random access preamble from the pool of random access preambles, and at least one selected C-RNTI from the pool of C-RNTIs from each selected handover candidate target access node.

5. The apparatus of claim 4, wherein the conditional fast handover command transmitted to the at least one user equipment further identifies the one or more handover candidate target access nodes, and comprises the default radio resource control configuration information for the one or more handover candidate target access nodes.

6. The apparatus of any of claims 1 to 5, wherein the apparatus further comprises means for determining a condition for carrying out the conditional fast handover of the at least one user equipment to at least one of the one or more handover candidate target access nodes, andwherein the conditional fast handover command transmitted to the at least one user equipment further comprises the condition.

7. The apparatus of any of claims 1 to 6, wherein the apparatus further comprises means for transmitting, to the one or more handover candidate target access nodes, handover information in association with the at least one user equipment, the handover information comprising at least one selected random access preamble, at least one selected cell radio network temporary identifier (C-RNTI), and user equipment context information.

8. A method comprising:receiving, by a handover source access node from one or more handover candidate target access nodes, one or more default radio resource control configurations comprising default radio resource control configuration information for a handover;receiving, from at least one user equipment, a measurement report comprising information on a radio service quality in association with the handover source access node and / or with at least one radio cell provided by the one or more handover candidate target access nodes;determining, by the handover source access node, to carry out the handover of the at least one user equipment to at least one of the one or more handover candidate target access nodes based on the measurement report, and that the handover is a conditional fast handover based on service delay requirements and / or service reliability requirements; and transmitting a conditional fast handover command to the at least one user equipment, wherein the conditional fast handover command comprises the default radio resource control configuration information.

9. The method of claim 8, wherein receiving the one or more default radio resource control configurations comprises:receiving, from the one or more handover candidate target access nodes, one or more radio access node configuration update messages comprising the one or more default radio resource control configurations; andtransmitting, to the one or more handover candidate target access nodes, one or more radio access node configuration update acknowledge messages in response to the one or more radio access node configuration update messages.

10. The method of claim 8 or claim 9, wherein the one or more default radio resource control configurations comprise information on at least one radio cell provided by the at least one of the one or more handover candidate target access nodes, a pool of random access preambles, and a pool of cell radio network temporary identifiers (C-RNTIs).

11. The method of claim 10, wherein the conditional fast handover command transmitted to the at least one user equipment comprises the one or more default radio resource control configurations, at least one selected random access preamble from the pool of random access preambles, and at least one selected C-RNTI from the pool of C-RNTIs from each selected handover candidate target access node.

12. The method of any of claims 8 to 11, wherein the method further comprises determining a condition for carrying out the conditional fast handover of the at least one user equipment to at least one of the one or more handover candidate target access nodes, andwherein the conditional fast handover command transmitted to the at least one user equipment further comprises the condition.

13. The method of any of claims 8 to 12, wherein the method further comprises transmitting, to the one or more handover candidate target access nodes, handover information in association with the at least one user equipment, the handover information comprising at least one selected random access preamble, at least one selected cell radio network temporary identifier (C-RNTI), and user equipment context information.

14. An apparatus comprising:means for generating, by a handover candidate target access node at least one default radio resource control configuration comprising default radio resource control configuration information for a fast handover;means for transmitting the at least one default radio resource control configuration to a handover source access node for the fast handover of at least one user equipment;means for receiving, from the at least one user equipment, a request for the fast handover, andmeans for carrying out the fast handover of the at least one user equipment to a radio cell provided by the handover candidate target access node using the default radio resource control configuration information.

15. The apparatus of claim 14, wherein the handover candidate target access node provides a plurality of radio cells, and the means for generating the at least one default radio resource control configuration comprises for each radio resource control configuration:means for generating a common part of the default radio resource control configuration that applies to the plurality of radio cells; andmeans for generating cell-specific parts of the default radio resource control configuration that apply to respective ones of the plurality of radio cells.

16. The apparatus of claim 14 or claim 15, wherein the means for transmitting the at least one default radio resource control configuration comprises:means for transmitting a radio access node configuration update message comprising the at least one default radio resource control configuration; andmeans for receiving, from the handover source access node, a radio access node configuration update acknowledge message in response to the radio access node configuration update message.

17. The apparatus of any of claims 14 to 16, wherein the apparatus further comprises:means for determining, by the handover candidate target access node, a change in the at least one default radio resource control configuration;means for generating, by the handover candidate target access node, at least one updated default radio resource control configuration based on the change; andmeans for transmitting the at least one updated default radio resource control configuration to the handover source access node.

18. The apparatus of any of claims 14 to 17, wherein the at least one default radio resource control configuration comprises information on at least one radio cell provided by the handover candidate target access node, a pool of random access preambles, and a pool of cell radio network temporary identifiers (C-RNTIs).

19. The apparatus of claim 18, wherein the apparatus further comprises meansfor receiving, from the handover source access node, handover information in association with the at least one user equipment, the handover information comprising at least one selected random access preamble, at least one selected C-RNTI, and user equipment context information.

20. The apparatus of claim 19, wherein the request for the fast handover received from the at least one user equipment comprises the at least one selected random access preamble and the at least one selected C-RNTI.

21. The apparatus of claim 18 or claim 19, wherein the apparatus further comprises means for generating a full configuration for the at least one user equipment based on the at least one default radio resource control configuration, and the handover information received from the handover source access node, andwherein the means for carrying out the handover comprises means for transmitting the full configuration to the at least one user equipment.

22. The apparatus of any of claims 18 to 21, wherein the request for the fast handover received from the at least one user equipment comprises at least one selected random access preamble and at least one selected C-RNTI, andwherein the means for carrying out the fast handover comprises means for obtaining, from the handover source access node, user equipment context information in association with the at least one user equipment.

23. A method comprising:generating, by a handover candidate target access node, at least one default radio resource control configuration comprising default radio resource control configuration information for a fast handover;transmitting the at least one default radio resource control configuration to a handover source access nodefor the fast handover of at least one user equipment;receiving, from the at least one user equipment, a request for the fast handover;andcarrying out the fast handover of the user equipment to a radio cell provided by the handover candidate target access node using the default radio resource control configuration information.

24. The method of claim 23, wherein the handover candidate target access node provides a plurality of radio cells, and generating the at least one default radio resource control configuration comprises for each radio resource control configuration:generating a common part of the default radio resource control configuration that applies to the plurality of radio cells; andgenerating cell-specific parts of the default radio resource control configuration that apply to respective ones of the plurality of radio cells.

25. The method of claim 23 or claim 24, wherein transmitting the at least one default radio resource control configuration comprises:transmitting a radio access node configuration update messages comprising at least one the default radio resource control configuration; andreceiving, from the handover source access node, a radio access node configuration update acknowledge message in response to the radio access node configuration update message.

26. The method of any of claims 23 to 25, wherein the default radio resource control configuration comprises information on at least one radio cell provided by the handover candidate target access node, a pool of random access preambles, and a pool of cell radio network temporary identifiers (C-RNTIs).

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