Method performed by first or second network device, user equipment and corresponding device

Abstract

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. The present disclosure provides a method for communication by a first network device in a wireless communication system. The method may comprise receiving a first message including radio link failure (RLF) report related to a user equipment (UE) from a second network device, wherein the RLF report includes information related to a time of an RLF; and adjusting a setting of a time window related to a conditional handover (CHO) based on the information related to the time of the RLF.

Description

METHOD PERFORMED BY FIRST OR SECOND NETWORK DEVICE, USER EQUIPMENT AND CORRESPONDING DEVICE

[0001] The present disclosure relates to the field of communication, and more specifically, to a method performed by a first network device, a method performed by a second network device, a method performed by a user equipment, the first network device, the second network device, and the user equipment.

[0002] 5G mobile communication technologies define broad frequency bands such that high transmission rates and new services are possible, and can be implemented not only in "Sub 6GHz" bands such as 3.5GHz, but also in "Above 6GHz" bands referred to as mmWave including 28GHz and 39GHz. In addition, it has been considered to implement 6G mobile communication technologies (referred to as Beyond 5G systems) in terahertz bands (for example, 95GHz to 3THz bands) in order to accomplish transmission rates fifty times faster than 5G mobile communication technologies and ultra-low latencies one-tenth of 5G mobile communication technologies.

[0003] At the beginning of the development of 5G mobile communication technologies, in order to support services and to satisfy performance requirements in connection with enhanced Mobile BroadBand (eMBB), Ultra Reliable Low Latency Communications (URLLC), and massive Machine-Type Communications (mMTC), there has been ongoing standardization regarding beamforming and massive MIMO for mitigating radio-wave path loss and increasing radio-wave transmission distances in mmWave, supporting numerologies (for example, operating multiple subcarrier spacings) for efficiently utilizing mmWave resources and dynamic operation of slot formats, initial access technologies for supporting multi-beam transmission and broadbands, definition and operation of BWP (BandWidth Part), new channel coding methods such as a LDPC (Low Density Parity Check) code for large amount of data transmission and a polar code for highly reliable transmission of control information, L2 pre-processing, and network slicing for providing a dedicated network specialized to a specific service.

[0004] Currently, there are ongoing discussions regarding improvement and performance enhancement of initial 5G mobile communication technologies in view of services to be supported by 5G mobile communication technologies, and there has been physical layer standardization regarding technologies such as V2X (Vehicle-to-everything) for aiding driving determination by autonomous vehicles based on information regarding positions and states of vehicles transmitted by the vehicles and for enhancing user convenience, NR-U (New Radio Unlicensed) aimed at system operations conforming to various regulation-related requirements in unlicensed bands, NR UE Power Saving, Non-Terrestrial Network (NTN) which is UE-satellite direct communication for providing coverage in an area in which communication with terrestrial networks is unavailable, and positioning.

[0005] Moreover, there has been ongoing standardization in air interface architecture / protocol regarding technologies such as Industrial Internet of Things (IIoT) for supporting new services through interworking and convergence with other industries, IAB (Integrated Access and Backhaul) for providing a node for network service area expansion by supporting a wireless backhaul link and an access link in an integrated manner, mobility enhancement including conditional handover and DAPS (Dual Active Protocol Stack) handover, and two-step random access for simplifying random access procedures (2-step RACH for NR). There also has been ongoing standardization in system architecture / service regarding a 5G baseline architecture (for example, service based architecture or service based interface) for combining Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies, and Mobile Edge Computing (MEC) for receiving services based on UE positions.

[0006] As 5G mobile communication systems are commercialized, connected devices that have been exponentially increasing will be connected to communication networks, and it is accordingly expected that enhanced functions and performances of 5G mobile communication systems and integrated operations of connected devices will be necessary. To this end, new research is scheduled in connection with eXtended Reality (XR) for efficiently supporting AR (Augmented Reality), VR (Virtual Reality), MR (Mixed Reality) and the like, 5G performance improvement and complexity reduction by utilizing Artificial Intelligence (AI) and Machine Learning (ML), AI service support, metaverse service support, and drone communication.

[0007] Furthermore, such development of 5G mobile communication systems will serve as a basis for developing not only new waveforms for providing coverage in terahertz bands of 6G mobile communication technologies, multi-antenna transmission technologies such as Full Dimensional MIMO (FD-MIMO), array antennas and large-scale antennas, metamaterial-based lenses and antennas for improving coverage of terahertz band signals, high-dimensional space multiplexing technology using OAM (Orbital Angular Momentum), and RIS (Reconfigurable Intelligent Surface), but also full-duplex technology for increasing frequency efficiency of 6G mobile communication technologies and improving system networks, AI-based communication technology for implementing system optimization by utilizing satellites and AI (Artificial Intelligence) from the design stage and internalizing end-to-end AI support functions, and next-generation distributed computing technology for implementing services at levels of complexity exceeding the limit of UE operation capability by utilizing ultra-high-performance communication and computing resources.

[0008] In order to meet an increasing demand for wireless data communication services since a deployment of 4G communication system, efforts have been made to develop an improved 5G or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also referred to as "beyond 4G network" or "post LTE system".

[0009] Wireless communication is one of the most successful innovations in modern history. Recently, a number of subscribers of wireless communication services has exceeded 5 billion, and it continues growing rapidly. With the increasing popularity of smart phones and other mobile data devices (such as tablet computers, notebook computers, netbooks, e-book readers and machine-type devices) in consumers and enterprises, a demand for wireless data services is growing rapidly. In order to meet rapid growth of mobile data services and support new applications and deployments, it is very important to improve efficiency and coverage of wireless interfaces.

[0010] According to an aspect of the present disclosure, there is provided a method for communication by a first network device in a wireless communication system. The method may comprise receiving a first message including radio link failure (RLF) report related to a user equipment (UE) from a second network device, wherein the RLF report includes information related to a time of an RLF; and adjusting a setting of a time window related to a conditional handover (CHO) based on the information related to the time of the RLF.

[0011] According to an aspect of the present disclosure, there is provided a method for communication by a second network device in a wireless communication system is provided. The method may comprise receiving a first message including radio link failure (RLF) report related to a user equipment from the UE, wherein the RLF report includes information related to a time of the RLF; and transmitting a second message including the RLF report to a first network device.

[0012] According to an aspect of the present disclosure, there is provided a first network device in a wireless communication system. The first network device may comprise a transceiver; and at least one processor coupled to the transceiver. The at least one processor may be configured to: receive a first message including radio link failure (RLF) report related to a user equipment (UE) from a second network device, wherein the RLF report includes information related to a time of an RLF; and adjust a setting of a time window related to a conditional handover (CHO) based on the information related to the time of the RLF.

[0013] According to an aspect of the present disclosure, there is provided a method performed by a first network device, comprising: receiving a first container from a second network device, wherein the first container includes a radio link failure (RLF) report received by the second network device from a user equipment (UE), and the RLF report includes a time window related message; and adjusting a setting of a time window based on the time window related message in the RLF report.

[0014] According to the method performed by the first network device provided by the present disclosure, wherein the time window related message includes at least one of: first time indication information for indicating a duration from a time at which the time window starts to a time at which the RLF is detected; second time indication information for indicating a duration from a time at which the time window ends to the time at which the RLF is detected; third time indication information for indicating a duration from the time at which the RLF is detected to the time at which the time window starts; fourth time indication information for indicating a duration from the time at which the RLF is detected to the time at which the time window ends; fifth indication information for indicating whether the time window ends when the RLF occurs; sixth indication information for indicating whether the time window starts when the RLF occurs; seventh indication information for indicating that the time window ends or starts too early; eighth indication information for indicating that the time window starts or ends too late.

[0015] According to the method performed by the first network device provided by the present disclosure, wherein the receiving of the first container from the second network device comprises: receiving the first container from the second network device via a core network node.

[0016] According to the method performed by the first network device provided by the present disclosure, wherein the method further comprises: transmitting a radio resource control (RRC) Reconfiguration message to the user equipment, wherein the RRC Reconfiguration message includes a configuration on the time window and a conditional event.

[0017] According to an aspect of the present disclosure, there is provided a method performed by a user equipment, comprising: generating a radio link failure (RLF) report including a time window related message; and transmitting to a second network device a first message including the RLF report.

[0018] According to the method performed by the user equipment provided by the present disclosure, wherein the generating of the radio link failure (RLF) report comprises: determining a duration from a time at which a time window starts to a time at which the RLF is detected; or determining a duration from a time at which the time window ends to the time at which the RLF is detected; or determining a duration from the time at which the RLF is detected to the time at which the time window starts; or determining a duration from the time at which the RLF is detected to the time at which the time window ends; or deciding whether the time window ends when the RLF occurs; or / and deciding whether the time window starts when the RLF occurs; or / and deciding whether the time window is too early; or / and deciding whether the time window is too late; the UE saves a result of the determining or deciding in the RLF report.

[0019] According to the method performed by the user equipment provided by the present disclosure, wherein the time window related message includes at least one of: first time indication information for indicating a duration from a time at which the time window starts to a time at which the RLF is detected; second time indication information for indicating a duration from a time at which the time window ends to the time at which the RLF is detected; third time indication information for indicating a duration from the time at which the RLF is detected to the time at which the time window starts; fourth time indication information for indicating a duration from the time at which the RLF is detected to the time at which the time window ends; fifth indication information for indicating whether the time window ends when the RLF occurs; sixth indication information for indicating whether the time window starts when the RLF occurs; seventh indication information for indicating that the time window ends or starts too early; eighth indication information for indicating that the time window starts or ends too late.

[0020] According to an aspect of the present disclosure, there is provided a method performed by a user equipment, comprising: receiving from a first network device a radio resource control (RRC) Reconfiguration message including a configuration on a time window and a conditional event; deciding whether the configuration on the time window is reasonable; transmitting a radio resource control (RRC) Reconfiguration Complete message or an RRC Setup message to a candidate cell based on the configuration on the time window.

[0021] According to the method performed by the user equipment provided by the present disclosure, wherein the transmitting of the radio resource control (RRC) Reconfiguration Complete message or the RRC Setup message to a candidate cell based on the configuration on the time window comprises: deciding that the time window is too late based on the configuration on the time window and the conditional event; transmitting the radio resource control (RRC) Reconfiguration Complete message to the candidate cell, wherein the RRC Reconfiguration Complete message contains an identity of the UE in a source cell.

[0022] According to the method performed by the user equipment provided by the present disclosure, wherein the transmitting of the radio resource control (RRC) Reconfiguration Complete message or the RRC Setup message to a candidate cell based on the configuration on the time window comprises: deciding that the time window is too early or too late based on the configuration on the time window and the conditional event; transmitting the RRC Setup message to the candidate cell.

[0023] According to an aspect of the present disclosure, there is provided a method performed by a second network device, comprising: receiving a first message transmitted by a user equipment (UE), wherein the first message includes an RLF report, and the RLF report includes a time window related message; and transmitting the RLF report to a first network device.

[0024] According to the method performed by the second network device provided by the present disclosure, wherein the time window related message includes at least one of: first time indication information for indicating a duration from a time at which the time window starts to a time at which the RLF is detected; second time indication information for indicating a duration from a time at which the time window ends to the time at which the RLF is detected; third time indication information for indicating a duration from the time at which the RLF is detected to the time at which the time window starts; fourth time indication information for indicating a duration from the time at which the RLF is detected to the time at which the time window ends; fifth indication information for indicating whether the time window ends when the RLF occurs; sixth indication information for indicating whether the time window starts when the RLF occurs; seventh indication information for indicating that the time window ends or starts too early; eighth indication information for indicating that the time window starts or ends too late.

[0025] According to the method performed by the second network device provided by the present disclosure, wherein the method further comprises: transmitting to the user equipment a second message including information for requesting the RLF report.

[0026] According to another aspect of the present disclosure, there is provided a first network device comprising: a transceiver configured to transmit and receive signals with the outside; and a controller configured to control the transceiver to perform the above method performed by the first network device.

[0027] According to another aspect of the present disclosure, there is provided a second network device comprising: a transceiver configured to transmit and receive signals with the outside; and a controller configured to control the transceiver to perform the above method performed by the second network device.

[0028] According to another aspect of the present disclosure, there is provided a user equipment comprising: a transceiver configured to transmit and receive signals with the outside; and a controller configured to control the transceiver to perform the above method performed by the user equipment.

[0029] According to another aspect of the present disclosure, there is provided a non-transitory computer-readable recording medium having stored thereon a program which, when being executed by a computer, performs any of the above methods.

[0030] Fig. 1 is an exemplary system architecture of System Architecture Evolution (SAE).

[0031] Fig. 2 is an exemplary system architecture according to various embodiments of the present disclosure.

[0032] Fig. 3 is a diagram of a method for supporting self-configuration and self-optimization according to an embodiment of the present disclosure.

[0033] Fig. 4 is a flowchart of a method performed by a user equipment according to an embodiment of the present disclosure.

[0034] Fig. 5 is a block diagram of a network node according to an embodiment of the present disclosure.

[0035] Fig. 6 is a block diagram of a user equipment according to an embodiment of the present disclosure.

[0036] In order to make the objectives, technical schemes and advantages of the embodiments of the present disclosure, a clearly and complete description will be made with respect to the technical schemes of the embodiments of the present disclosure, in conjunction with the accompanying drawings of the embodiments of the present disclosure. Apparently, the described embodiments are a part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary skilled in the art without creative labor belong to the protection scope of the present disclosure.

[0037] Before undertaking the detailed description below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document. The term "couple" and its derivatives refer to any direct or indirect communication between two or more elements, whether those elements are in physical contact with one another. The terms "transmit," "receive," and "communicate," as well as derivatives thereof, encompass both direct and indirect communication. The terms "include" and "comprise," as well as derivatives thereof, mean inclusion without limitation. The term "or" is inclusive, meaning and / or. The phrase "associated with," as well as derivatives thereof, means to include, be included within, interconnect to or with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, have a relationship to or with, or the like. The term "controller" means any device, system or part thereof that controls at least one operation. Such a controller may be implemented in hardware or a combination of hardware and software and / or firmware. The function associated with any particular controller may be centralized or distributed, whether locally or remotely. The phrase "at least one of," when used with a list of items, means that different combinations of one or more of the listed items may be used, and only one item in the list may be needed. For example, "at least one of: A, B, and C" includes any of the following combinations: A, B, C, A and B, A and C, B and C, and A and B and C. For example, "at least one of A, B, or C " includes any of the following combinations: A, B, C, A and B, A and C, B and C, and A and B and C.

[0038] In addition, various functions described below can be implemented or supported by one or more computer programs, each of which is formed by computer-readable program code and embodied in a computer-readable medium. The terms "application" and "program" refer to one or more computer programs, software components, instruction sets, procedures, functions, objects, classes, instances, related data or parts thereof appropriate for implementation in suitable computer-readable program code. The phrase "computer readable program code" includes any type of computer code, including source code, objective code and executable code. The phrase "computer readable medium" includes any type of medium that can be accessed by a computer, such as Read-Only Memory (ROM), Random Access Memory (RAM), hard disk drive, compact disk (CD), digital video disk (DVD) or any other type of memory. A "non-transitory" computer-readable medium excludes wired, wireless, optical or other communication links that transfer transitory electrical or other signals. A non-transitory computer-readable medium includes a medium in which data can be stored permanently and a medium in which data can be stored and rewritten later, such as rewritable optical disks or erasable memory devices.

[0039] The terms used herein to describe the embodiments of the present application is not intended to limit and / or define the scope of the present application. For example, unless otherwise defined, the technical or scientific terms used in the present disclosure should have ordinary meanings as understood by ordinary skilled in the art to which the present application belongs.

[0040] It should be understood that "first", "second" and similar words used in the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. Unless clearly indicated otherwise in the context, similar words such as "a", "an", "the" and the like in the singular form do not indicate a quantitative limitation, but indicate the existence of at least one.

[0041] As used herein, any reference to "one example" or "an example", "one embodiment" or "an embodiment" means that a particular element, feature, structure or characteristic described in conjunction with the embodiment is included in at least one embodiment. The appearances of the phrases "in one embodiment" or "in one example" in different places in the specification are not necessarily all referring to the same embodiment.

[0042] As used herein, "a part of" a certain thing means "at least some of" this thing, so it may mean being less than the entirety thereof or being the entirety thereof. Therefore, "a part of" the thing includes the whole thing as a special case, that is, an example in which the whole thing is a part of the thing.

[0043] It will be further understood that words such as "include", "contain" or the like means that the elements or objects appearing preceding the word encompass the elements or objects listed behind the word as well as their equivalents, without excluding other elements or objects. Words such as "connect", "interconnect" or the like are not limited to physical or mechanical connections, but may include electrical connection, whether direct or indirect. "Up", "Down", "Left" and "Right" are only used to indicate relative positional relationships. When the absolute position of the described object changes, accordingly, the relative positional relationship may change as well.

[0044] The various embodiments discussed below for describing the principle of the present disclosure in this patent document are for illustration only, and should not be construed as limiting the scope of the present disclosure in any way. Those skilled in the art will understand that the principle of the present disclosure may be implemented in any suitably arranged wireless communication system. For example, although the following detailed description of the embodiments of the present disclosure will focus on LTE and 5G communication systems, those skilled in the art can understand that the main points of the present disclosure can also be applied to other communication systems with similar technical backgrounds and channel formats, with slight modifications and basically without departing from the scope of the present disclosure. The schemes of the embodiments of the present application may be applied to various communication systems. For example, the communication systems may include a Global System for Mobile communications (GSM) system, a Code Division Multiple Access (CDMA) system, a Wideband Code Division Multiple Access (WCDMA) system, General Packet Radio Service (GPRS), Long Term Evolution (LTE) system, LTE Frequency Division Duplex (FDD) system, LTE Time Division Duplex (TDD), Universal Mobile Telecommunication System (UMTS), worldwide interoperability for microwave access (WiMAX) communication system, fifth generation (5th generation, 5G) system or New Radio (NR), etc. In addition, the schemes of the embodiments of the present application may be applied to future-oriented communication technologies. In addition, the schemes of the embodiments of the present application may be applied to future-oriented communication technologies.

[0045] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the present disclosure as defined by the claims and their equivalents. The description includes various specific details to assist in that understanding but should be regarded as exemplary only. Accordingly, the ordinary skilled in the art will recognize that various changes and modifications to the various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and structures may be omitted for clarity and conciseness.

[0046] The terms and wordings used in the following description and claims are not limited to the bibliographical meanings, but are merely used by the inventor to enable a clear and consistent understanding of the present disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustration purpose only, but not for the purpose of limiting the present disclosure as defined by the appended claims and their equivalents.

[0047] It should be understood that the singular forms "a," "an," and "the" include plural referents, unless clearly indicated otherwise in the context. Thus, for example, reference to "a component surface" includes reference to one or more of such surfaces.

[0048] The term "include" or "may include" refers to the existence of a corresponding disclosed function, operation or component which can be used in various embodiments of the present disclosure, and does not limit the existence of one or more additional functions, operations, or components. The terms "include" and / or "have" may be construed to represent certain characteristics, numbers, steps, operations, constituent elements, components or combinations thereof, but may not be construed to exclude the possibility of existence of one or more other characteristics, numbers, steps, operations, constituent elements, components or combinations thereof.

[0049] The term "or" used in various embodiments of the present disclosure includes any of the listed terms or all combinations thereof. For example, "A or B" may include A, may include B, or may include both A and B.

[0050] Unless defined differently, all terms used in the present disclosure, including technical or scientific terms, have the same meanings as those understood by the skilled in the art as described in the present disclosure. Common terms as defined in a dictionary are to be interpreted to have meanings consistent with the context in the relevant technical field o, and are not to be interpreted ideally or excessively, unless clearly defined as such in the present disclosure.

[0051] Figs. 1 to 6 discussed below and various embodiments for describing the principle of the present disclosure in this patent document are only for illustration, and should not be interpreted as limiting the scope of the present disclosure in any way. Those skilled in the art will understand that the principle of the present disclosure may be implemented in any suitably arranged system or device.

[0052] Fig. 1 is an exemplary system architecture 100 of system architecture evolution (SAE). A user equipment (UE) 101 is a terminal device for receiving data. An evolved universal terrestrial radio access network (E-UTRAN) 102 is a radio access network, which includes a macro base station (eNodeB / NodeB) that provides UE with interfaces to access the radio network. A mobility management entity (MME) 103 is responsible for managing mobility context, session context and security information for the UE. A service gateway (SGW) 104 mainly provides functions for user plane, and the MME 103 and the SGW 104 may be in a same physical entity. A packet data network gateway (PGW) 105 is responsible for functions such as charging, lawful interception, etc., and may be in a same physical entity with the SGW 104 as well. A policy and charging rule function entity (PCRF) 106 provides quality of service (QoS) policies and charging criteria. A general packet radio service support node (SGSN) 108 is a network node device that provides routing for data transmission in a universal mobile telecommunications system (UMTS). A home subscriber server (HSS) 109 is a home subsystem for the UE, and is responsible for protecting user information including a current position of the user equipment, an address of a service node, user security information, and packet data context of the user equipment, etc.

[0053] Fig. 2 is an exemplary system architecture 200 according to various embodiments of the present disclosure. Other embodiments of the system architecture 200 can be used without departing from the scope of the present disclosure.

[0054] A user equipment (UE) 201 is a terminal device for receiving data. A next generation radio access network (NG-RAN) 202 is a radio access network, which includes a base station (a gNB or an eNB connected to the 5G core network (5GC), and the eNB connected to the 5GC is also referred to as ng-gNB) that provides UE with interfaces to access the radio network. An access control and mobility management function entity (AMF) 203 is responsible for managing mobility context and security information for the UE. A user plane function entity (UPF) 204 mainly provides functions for user plane. A session management function entity (SMF) 205 is responsible for session management. A data network (DN) 206 includes, for example, services of the operators, access to the Internet and services of the third party.

[0055] The exemplary embodiments of the present disclosure are further described below with reference to the accompanying drawings.

[0056] The text and drawings are provided as examples only to help understand the present disclosure. They should not be construed as limiting the scope of the present disclosure in any way. Although certain embodiments and examples have been provided, based on the contents disclosed herein, it is obvious to those skilled in the art that changes can be made to the illustrated embodiments and examples without departing from the scope of the present disclosure.

[0057] In the case that a large number of UEs are required to hand over at the same time, a large number of UEs handing over at the same time will cause impact on the network and air interface, and bring a consequence of UE's radio link failure or unsuccessful handover. In order to improve the efficiency for handover and reduce the burden for the network and air interface, time window-based handover is defined in 3GPP release 17. The network can configure for a UE a time window during which the UE performs handover. By configuring different time windows for different UEs, a purpose for decentralizing UE's handover process can be achieved.

[0058] For time window-based handover, in a handover preparing process, a source base station transmits to a destination base station a Handover Request message carrying a conditional handover information request information element. Among other things, the conditional handover information request information element contains indication information of a start of a conditional handover, a possibility of an expected handover, and time window information. The time window contains a time at which the window for handover starts and a duration of the window. The destination base station infers, according to the time window information, that the UE will hand over to the destination base station within the time window, and the destination base station may reserve resources according to the time window information. The destination base station transmits to the source base station configuration information containing an identity of a destination cell and an RRC (Radio Resource Control) message to be transmitted to the UE. The source base station forwards the RRC message to the UE, in which the RRC message contains an identity of the conditional handover, as well as information on a related measurement configuration and a radio resource connection reconfiguration of the conditional handover. If the related measurement configuration of the conditional handover contains an identity of a destination cell to be measured and a conditional initiation configuration, the conditional initiation configuration contains a time window and an event of the conditional handover, for example, the conditional handover is a conditional event A3. If the related measurement configuration of the conditional handover is based on a time condition, the UE decides whether a condition for the time window to start is reached, and if so, it is further required to decide whether the event of the conditional handover is satisfied. If it is satisfied, the UE can hand over to the destination cell. When the time window of the conditional handover is set unreasonably, the quality of the UE's serving cell has caused a radio link failure before the time at which the time window starts. As such, the handover process fails.

[0059] As described above, if the time window is set unreasonably, a UE's radio link failure or handover failure will also be caused. At present, the time window-based handover needs be further enhanced to improve the system performance. However, it can be understood that the technical problems that can be solved by the present disclosure are not limited to this, the above technical problems are only provided as examples, and any technical problems that can be solved by the embodiments of the present disclosure belong to the scope to be protected by the present disclosure.

[0060] An embodiment of the present disclosure provide a method performed by a first network device (e.g., a source base station), comprising: receiving a first container from a second network device, wherein the first container includes a radio link failure (RLF) report received by the second network device from a user equipment (UE), and the RLF report includes a time window related message; and adjusting a setting of a time window based on the time window related message in the RLF report.

[0061] Through the above method, the self-configuration and self-optimization for time window are realized, and the occurrence of failure is reduced.

[0062] It should be noted that in the present invention, the time at which the time window starts can be counted in units of 10ms as a number of UTC seconds since 00: 00: 00 on January 1st, 1900 AD (the midnight between Sunday, December 31st, 1899 and Monday, January 1st, 1900), and the duration of the time window can be in milliseconds or multiples of milliseconds. Other expressions are also possible, which is not limited by the present invention.

[0063] The NR (New Radio) and LTE (Long Term Evolution) in the following description are merely examples of different RATs (Radio Access Technologies), and other RATs are also possible, which is not limited by the present invention. Moreover, it can be understood that the present invention can also be extended to other communication systems, such as 6G communication systems and the like.

[0064] Please refer to Fig. 3, which is a diagram of a method for supporting self-configuration and self-optimization according to an embodiment of the present disclosure.

[0065] As shown in Fig. 3, a source cell is configured with a conditional handover, a UE has not handed over to a candidate cell, and an RLF is detected in the source cell, or an RLF occurs. The UE saves some information in an RLF report, and then accesses to another base station (BS), such as base station 2. The base station 2 obtains the RLF report of the UE, and transmits the RLF report to a source base station. The source base station analyses whether the conditional handover is appropriate. The method comprises the following steps:

[0066] Step 301: The source base station requests CHO (Conditional Handover) for one or more candidate cells. If there are a plurality of candidate cells, the plurality of candidate cells may belong to one or more candidate base stations. The source base station transmits a Handover Request message to a candidate base station. The cell for the handover request corresponds to each of the candidate cells. The Handover Request message includes an identity allocated by the source base station for the UE, a unique identity of a candidate cell or a destination cell, an encrypting capability of the UE, information on a PDU session to be set up, context information of RRC, and information on a conditional handover request. The conditional handover request contains a time window, which contains a starting time and a window duration.

[0067] A candidate base station or candidate cell reserves resources according to the information on the time window. If the time window expires and the UE has not appeared in the destination candidate cell, the candidate cell may consider that the UE has selected another candidate cell, or that the conditional handover has been cancelled, so that it may release the reserved resources. In an implementation, the candidate cell may keep the pre-allocated resources for a period of time after the time window expires.

[0068] Step 302: The source base station receives a Handover Request Acknowledgement message from the candidate base station. The Handover Request Acknowledgement message is for each of the candidate cells.

[0069] This message contains a destination base station-to-source base station transparent container. For the conditional handover, this container contains RRC reconfiguration information configured by the candidate cell for the UE.

[0070] Step 303: The source base station transmits an RRC Reconfiguration message to the UE.

[0071] This message contains conditional reconfiguration information. The conditional reconfiguration information includes a list of conditional reconfiguration additions and modifications, the list of the additions and modifications includes an identity of conditional reconfiguration, an identity of the candidate cell, a configuration of CHO execution conditions (which is also a configuration of measurement and reporting), and RRC reconfiguration information corresponding to the execution conditions. Upon the receipt of this message, the UE may transmit an RRC Reconfiguration Complete message to the source base station in step 304, indicating that the RRC Reconfiguration message has been received.

[0072] The configuration of CHO execution conditions is also referred to as configuration of conditional triggers or configuration of conditional handovers. The UE performs measurement on the candidate cell to decide whether this cell satisfies the CHO execution conditions. When this cell satisfies the execution conditions, the UE will select this candidate cell to be the destination cell as a new serving cell. Then the UE synchronizes with the new serving cell and transmits an RRC Reconfiguration Complete message to the new cell. As such, the conditional handover is completed.

[0073] For time-based conditional handover, the CHO execution conditions contain a setting of a time window and a setting of a conditional event. The time window contains a starting time and a window duration. The starting time, which may also be referred to as time T1, indicates a time at which the UE can start to select the new serving cell. The starting time plus the window duration, which may also be referred to as time T2, indicates a time before which the UE would set up a connection with the new serving cell. The candidate cell pre-allocates resources according to the time window. After the time window expires, if no RRC Reconfiguration Complete transmitted by the UE is received, the candidate cell may consider that the UE has selected another cell, and thus release the pre-allocated resources. In addition to the time window, the CHO execution conditions further contains a conditional event, which restricts quality of signal of the candidate cell and / or serving cell. For example, the conditional event is set to a conditional event A3. The conditional event A3 refers to that the quality of signal of a neighboring cell is higher than that of the current serving cell by a threshold value, then the conditional event of CHO is triggered, and the UE can select the neighboring cell as the new serving cell. For time-based conditional handover, the UE decides whether the conditional event is satisfied within a duration of the time window. If a certain candidate cell satisfies the conditional event within the time window, it is considered that the conditional handover is satisfied and can be performed. Then the UE can leave the source cell / source base station. According to the RRC related configuration information corresponding to the candidate cell, the UE initiates a synchronizing process to the candidate cell, transmits, after synchronization, an RRC Reconfiguration Complete message to the candidate cell, and selects the destination cell as the new serving cell. As such, the conditional handover is completed.

[0074] The time window is related to the resources allocated by the candidate cell, and is also related to the time at which the UE selects the candidate cell, therefore, it greatly affects whether the conditional handover can be successful. When the time window in the execution conditions is set unreasonably, the situations as follows may occur:

[0075] The time window starts too late, the quality of the UE's serving cell has got worse before the time at which the time window starts, and the quality of the neighboring cell is good enough. Being good enough means that the conditional event has been satisfied. If the UE can, only within the time window, select a candidate cell whose quality satisfies the conditional event, transmit a synchronization and RRC Reconfiguration Complete message to the candidate cell, then a radio link failure will occur for the UE in the source cell since the time window starts too late. If the UE may transmit the synchronization and RRC Reconfiguration Complete message to the candidate cell whose quality satisfies the conditional event only according to the conditional event, there will be a problem that, the candidate cell reserves resources according to the time window, if the time window is set to be too late, the candidate cell will receive the RRC Reconfiguration Complete message before the time window starts, and the candidate cell cannot properly analyze the RRC Reconfiguration Complete message.

[0076] The time window starts too early, or the duration of the time window is set to be too short, that is, during the duration of the time window, the quality of the neighboring cell has not reached a good enough level, the conditional event is not satisfied, and the conditional handover cannot be performed; and when the quality of the neighboring cell satisfies the conditional handover, the time window has expired and is over. If the UE can, only within the time window, select a candidate cell whose quality satisfies the conditional event, then a radio link failure will occur for the UE in the source cell as the quality of the source cell gets worse. If the UE may transmit the synchronization and RRC Reconfiguration Complete message to the candidate cell whose quality satisfies the conditional event only according to the conditional event, there will be another problem that, if the time window is too early, when the RRC Reconfiguration Complete message is received, the candidate cell has released the pre-allocated resources and the context information of the UE, so that the RRC Reconfiguration Complete cannot be received normally.

[0077] If a radio link failure (RLF) occurs for the UE in the cell of the source base station, in the following description, the radio link failure (RLF) may also refer to handover failure, the RLF failure related information may also contain handover failure information, and the UE saves the radio link failure information or handover failure information in a variable of RLF report. After an RLF occurs for the UE, according to a result of measurement, the UE may select another cell with good quality of signal and reset up an RRC connection with this cell. In the process of transmitting to the cell an RRC Setup Request and an RRC Setup, the UE informs the network that the UE has saved an RLF report, and the network may decide whether to obtain the RLF report from the UE. In this process, the UE records one or more pieces of information in the following and contains the one or more pieces of information in the RLF report:

[0078] An identity of a cell where an RLF occurs. The cell identity can be a unique cell identity (CGI), or a physical layer cell identity (PCI), or another identity.

[0079] A measurement result. The measurement result contains a result of a measurement on the serving cell, the source cell, the destination cell and the neighboring cell. The measurement result contains a cell identity and a measurement value for quality of air interface of the cell. The cell identity can be a unique cell identity (CGI), or a physical layer cell identity (PCI), or another identity. The measurement value can be information such as RSRP (Reference Signal Receiving Power) and RSRQ (Reference Signal Receiving Quality) of the cell, etc.

[0080] An identity of a reset-up cell. After an RLF occurs for the UE, the UE may reselect a cell, initiate an RRC Connection Setup in the reselected cell, which is the reset-up cell. The cell identity can be a unique cell identity (CGI), or a physical layer cell identity (PCI), or another identity.

[0081] T1: A duration from a time of RLF to a time of RRC Setup Complete (timeUntilReconnection-r16). The UE performs cell reselection and sets up an RRC connection in the reselected cell, and the UE saves, in the RLF report, the duration from the occurrence of RLF to the time of transmitting an RRC Setup Complete.

[0082] T2: A duration from the execution of HO (handover) to the detection of RLF (timeConnFailure).

[0083] T3: A duration from the last execution of DAPS handover to the detection of RLF in the source cell (timeConnSourceDAPS-Failure) (T304 is running). The value is in milliseconds.

[0084] T4: A duration from the occurrence of RLF to the reception of UE Information Request (timeSinceFailure). If the UE later receives the UE Information Request transmitted by the base station, asking the UE to transmit the RLF report to the base station, then the UE records the duration from the occurrence of RLF to the reception of UE Information Request (timeSinceFailure). This duration records how long since the RLF occurred, until the UE transmits the RLF report to the base station.

[0085] T5: A duration from the time of the last execution of CHO (Conditional Handover) to the time of the reception of the latest conditional reconfiguration (timeSinceCHO-Reconfig).

[0086] A list of CHO candidate cells: The list contains unique cell identities or physical layer cell identities.

[0087] T6: A duration from the time at which the time window starts to the time at which the RLF is detected; and the time window is obtained in step 303 from the RRC message transmitted by the source base station.

[0088] T7: A duration from the time at which the time window ends to the time at which the RLF is detected;

[0089] T8: A duration from the time at which the RLF is detected to the time at which the window starts;

[0090] T9: A duration from the time at which the RLF is detected to the time at which the window ends;

[0091] Indication information of whether the time window ends, or indication information that the time window ends: indicates whether the time window has expired and closed when the RLF occurs.

[0092] Indication information of whether the time window starts, or indication information that the time window starts, or indication information that the event window has not yet started: indicates whether the time window has started when the RLF occurs, or whether the time window has started and has not expired when the RLF occurs.

[0093] Information indicating that the time window ends or starts too early. If, when the time window ends, there is none of candidate cells whose quality satisfies the setting of conditional event in the conditional handover (CHO) execution condition, that is, no candidate cell satisfies the requirement of the quality of handover, then the conditional event of handover is not triggered, and the UE can neither hand over to a new serving cell, nor can perform time window-based handover, and still remains in the original serving cell (source cell). When the quality of the original serving cell has gradually got worse, and the quality of a certain candidate cell has gradually got better, since the time window has ended, the UE cannot perform event-based handover and still remains in the source cell. Because of the poor quality of signal of the source cell, an RLF occurs for the UE in the source cell. For the RLF occurring at this time, the time window may be considered as being unreasonably set, which is an error of time window being too early.

[0094] Information indicating that the time window starts or ends too late. When the quality of the candidate cell satisfies the conditional event, the time window has not yet started. If the operation of the UE is that only when the quality of the candidate cell satisfies the conditional event, and specifically the quality of the candidate cell satisfies the conditional event within the time period of the time window, the UE can select the candidate cell as the new serving cell, since the time window has not yet started, the UE cannot perform time-based handover and still remains in the original serving cell (source cell), and the quality of the original serving cell has gradually got worse, and an RLF occurs for the UE in the source cell. This RLF may occur before the start of the time window, or during the duration of the time window, or after the end of the time window. In a word, this situation is caused by unreasonable setting of time window and late starting of time window, which is an error of time window being too late.

[0095] An identity of an appropriate cell. The appropriate cell identity information or reconnected cell identity information contains a global cell identity and / or a tracking area code (TAC) of the cell. The appropriate cell or reconnected cell is a cell appropriate for the UE to access after a failure, or a cell where the UE is reconnected successfully.

[0096] Step 305: The UE connects to the base station 2. The UE transmits an RRC Connection Request or an RRC Connection Reset-up Request message to the base station 2. The base station 2 transmits an RRC Connection Setup or RRC Connection Reset-up message to the UE. The UE transmits an RRC Connection Setup Complete or RRC Connection Reset-up Complete message to the base station 2.

[0097] The cell which is successfully reconnected contains a cell where the UE successfully completes an RRC re-setup process, or a cell where the UE successfully completes an RRC connection setup process.

[0098] The RRC Connection Setup Complete or RRC Connection Reset-up Complete message contains RLF available information. If there is information of radio link failure or handover failure in the variable of RLF report and a registered PLMN is contained in a list of PLMN identities of the maintained variable of RLF report, the RLF available information is contained the RRC Connection Setup Complete or RRC Connection Reset-up Complete message.

[0099] Step 306: The base station 2 transmits a UE Information Request message to the UE. The base station 2 transmits a UE Information Request message to the UE after receiving the RLF available information.

[0100] Step 307: The UE transmits a UE Information Request Response message to the base station 2. The UE Information Request Response message contains an RLF report. The RLF report contains at least one piece of the following information:

[0101] An identity of a cell where an RLF occurs. The cell identity can be a unique cell identity (CGI), or a physical layer cell identity (PCI), or another identity.

[0102] A UE's measurement result. The measurement result contains a result of a measurement on the serving cell, the source cell, the destination cell and the neighboring cell. The measurement result contains a cell identity and a measurement value for quality of air interface of the cell. The cell identity can be a unique cell identity (CGI), or a physical layer cell identity (PCI), or another identity. The measurement value can be information such as RSRP (Reference Signal Receiving Power) and RSRQ (Reference Signal Receiving Quality) of the cell, etc.

[0103] An identity of a reset-up cell. The cell identity can be a unique cell identity (CGI), or a physical layer cell identity (PCI), or another identity.

[0104] T1: A duration from a time of RLF to a time of RRC Setup Complete (timeUntilReconnection-r16).

[0105] T2: A duration from the execution of HO to the detection of RLF (timeConnFailure).

[0106] T3: A duration from the last execution of DAPS handover to the detection of RLF in the source cell (TimeconnSourceDAPs-failure) (T304 is running). The value is in milliseconds.

[0107] T4: A duration from the occurrence of RLF to the reception of UE Information Request (timeSinceFailure);

[0108] T5: A duration from the time of the last execution of CHO to the time of the reception of the latest conditional reconfiguration (timeSinceCHO-Reconfig).

[0109] A list of CHO candidate cells: The list contains unique cell identities or physical layer cell identities.

[0110] T6: A duration from the time at which the time window starts to the time at which the RLF is detected; and the time window is obtained in step 303 from the RRC message transmitted by the source base station.

[0111] T7: A duration from the time at which the time window ends to the time at which the RLF is detected;

[0112] T8: A duration from the time at which the RLF is detected to the time at which the window starts;

[0113] T9: A duration from the time at which the RLF is detected to the time at which the window ends;

[0114] Indication information of whether the time window ends, or indication information that the time window ends: indicates whether the time window has expired and closed when the RLF occurs.

[0115] Indication information of whether the time window starts, or indication information that the time window starts, or indication information that the event window has not yet started: indicates whether the time window has started when the RLF occurs, or whether the time window has started and has not expired when the RLF occurs.

[0116] Information indicating that the time window ends or starts too early. If, when the time window ends, there is none of candidate cells whose quality satisfies the setting of conditional event in the conditional handover (CHO) execution condition, that is, no candidate cell satisfies the requirement of the quality of handover, then the conditional event of handover is not triggered, and the UE can neither hand over to a new serving cell, nor can perform time window-based handover, and still remains in the original serving cell (source cell). When the quality of the original serving cell has gradually got worse, and the quality of a certain candidate cell has gradually got better, since the time window has ended, the UE cannot perform event-based handover and still remains in the source cell. Because of the poor quality of signal of the source cell, an RLF occurs for the UE in the source cell. For the RLF occurring at this time, the time window may be considered as being unreasonably set, which is an error of time window being too early.

[0117] Information indicating that the time window starts or ends too late. When the quality of the candidate cell satisfies the conditional event, the time window has not yet started. If the operation of the UE is that only when the quality of the candidate cell satisfies the conditional event, and specifically the quality of the candidate cell satisfies the conditional event within the time period of the time window, the UE can select the candidate cell as the new serving cell, since the time window has not yet started, the UE cannot perform time-based handover and still remains in the original serving cell (source cell), and the quality of the original serving cell has gradually got worse, and an RLF occurs for the UE in the source cell. This RLF may occur before the start of the time window, or during the duration of the time window, or after the end of the time window. In a word, this situation is caused by unreasonable setting of time window and late starting of time window, which is an error of time window being too late.

[0118] An identity of an appropriate cell. The appropriate cell identity information or reconnected cell identity information contains a global cell identity and / or a tracking area code (TAC) of the cell. The appropriate cell or reconnected cell is a cell appropriate for the UE to access after a failure, or a cell where the UE is reconnected successfully.

[0119] Step 308: The base station 2 transmits the received RLF report to the base station where the cell for which a failure occurs is located. Here, the base station where the cell for which a failure occurs is located is the source base station. Among other things, the base station 2 can be a base station which supports the same radio access technology as the source base station, or a base station which supports a different radio access technology, and the base station 2 can be a base station which supports the same system as the source base station, or a base station under a different access system.

[0120] The base station 2 transmits the RLF report received from the UE to the source base station through the inter-base station interface, or transmits the RLF report received from the UE to the source base station through the core network.

[0121] If the base station 2 and the source base station are both under the same access system, for example, both under the NR system, the base station 2 may transmit the RLF report to the source base station through an RLF indication message of the inter-base station interface. The base station 2 may also transmit the RLF report to the source base station through another inter-base station interface message.

[0122] If there is no interface between the base station 2 and the source base station or the base station 2 and the source base station are base stations of different systems, the base station 2 transmits the RLF report to the source base station through the core network.

[0123] The source base station detects the reason for the occurrence of the failure. According to the T6 (the duration from the time at which the time window starts to the time at which the RLF is detected) contained in the RLF report, in combination with the time window duration saved by the source base station, the source base station gets to know that the time window has expired and closed when the RLF occurs. At this time, the UE does not satisfy the condition for conditional handover, and fails to hand over to the candidate destination cell. From the measurement result contained in the RLF report, the source base station can get to know that the quality of the candidate cell is already very good and the quality of the serving cell is getting worse. However, the UE does not perform conditional handover, so the source base station will get to know that one reason is that the event in the configured conditional handover is unreasonable, so that the UE initiates the handover event too late, the configured time window is too early, or the duration is configured to be too short. Because the time window is configured unreasonably, the UE fails to perform conditional handover.

[0124] According to the T7 (the duration from the time at which the time window ends to the time at which the RLF is detected) contained in the RLF report, the source base station gets to know that the time window has closed before the RLF and before the quality of the candidate cell gets good enough, so the source base station gets to know that the configured time window is too early or too short.

[0125] According to the T8 (the duration from the time at which the RLF is detected to the time at which the window starts) contained in the RLF report, the source base station gets to know that the time window will start only after the RLF. Although there is a candidate cell with a fine quality, because the time window has not yet started, the condition for handover is not satisfied, so the source base station gets to know that the configured time window is too delayed or too late.

[0126] According to the T9 (the duration from the time at which the RLF is detected to the time at which the window ends) contained in the RLF report, in combination with the time window duration saved by the source base station, the source base station gets to know that the time window will start only after the RLF. Although there is a candidate cell with a fine quality, because the time window has not yet started, and the condition for handover is not satisfied, so the source base station gets to know that the configured time window is too delayed or too late.

[0127] According to the indication information that the time window ends contained in the RLF report, in combination with that the identity of the cell where the RLF occurs indicates the source cell, also with reference to whether the quality of signal of the candidate cell is good enough in the measurement report, the source base station gets to know that the time window has closed when the RLF occurs and before the quality of the candidate cell gets good enough, so the source base station gets to know that the configured time window is too early or too short.

[0128] According to the indication information that the time window has not yet started contained in the RLF report, in combination with that the identity of the cell where the RLF occurs indicates the source cell, also with reference to whether the quality of signal of the candidate cell is good enough in the measurement report, the source base station gets to know that the time window has not yet started when the RLF occurs. Although the quality of the candidate cell is good enough, the condition for handover is not satisfied, so the source base station gets to know that the configured time window is too delayed or too late.

[0129] According to the derived decision, the source base station may adjust the setting of time window. When the time window-based handover is configured later, a new time window can be employed and configured to the UE, so as to improve the success rate for UE handover.

[0130] According to the information that the time window ends or starts too early contained in the RLF report, or according to the information that the time window starts or ends too late contained in the RLF report, the source base station can adjust the setting of time window. When the time-based handover is configured later, a new time window can be employed and configured to the UE, so as to improve the success rate for UE handover.

[0131] At this point, the method for supporting self-configuration and self-optimization in the present invention is completed. Through this method, in the case that the time window-based handover fails, the reason of the failure can be properly recognized for reasonable optimization. By adjusting the setting of time window, the occurrence of handover failure can be reduced, the continuity of service can be guaranteed, and the labor cost of operators can be reduced.

[0132] In addition, for the problem mentioned above, that is, the candidate cell reserves resources according to the time window, if the time window is set unreasonably, a problem will also be caused to the resources reservation by the candidate cell. Specifically, when the source cell configures CHO, it configures the UE with time window-based CHO handover. For time window-based conditional handover, the CHO execution conditions contain the setting of time window and the setting of conditional events. When the quality of the candidate cell is gradually getting better, the quality of the source cell is gradually getting worse. At the UE side, there are two kinds of actions, and which action to employ depends on the implementation:

[0133] Action 1: allowing the UE to hand over to the candidate cell if the quality of the candidate cell satisfies the conditional event.

[0134] Action 2: allowing the UE to hand over to the candidate cell only when the quality of the candidate cell satisfies the conditional event and specifically the quality of the candidate cell satisfies the conditional event within the time window.

[0135] When the source cell configures time window-based CHO, it also configures the time window to the base station where the candidate cell is located. The candidate cell reserves resources according to the time window. If the time window is set to be too late, it means that the resources are reserved only after the time window starts. Before the time window starts, the candidate cell does not reserve resources for the UE. The reserved resources include resources reserved for random access (RACH) and resources reserved for radio bearers, which contain signaling radio bearer and data radio bearer. If the UE is allowed to hand over to the candidate cell when the quality of the candidate cell satisfies the conditional event, then when the UE decides to hand over to the candidate cell, it first synchronizes with the candidate cell, and transmits, after the synchronization, an RRC Reconfiguration Complete message to the candidate cell. If the time window has not yet started, then the reserved resources have not been started, in which case the synchronization between the UE and the candidate cell will fail, or if the synchronization is completed, and the UE transmits an RRC Reconfiguration Complete message to the candidate cell, and the candidate cell has not allocated resources for signaling bearer, then the candidate cell cannot properly analyze the RRC Reconfiguration Complete message. If the time window is set to be too early, when the UE decides to hand over to the candidate cell, the candidate cell has released the pre-allocated resources and the context information of the UE, so that the RRC Reconfiguration Complete cannot be received normally, either. For example, the following embodiment can at least solve the problem that the RRC Reconfiguration Complete cannot be properly performed, but not limited to this.

[0136] Please refer to Fig. 4, which is a flowchart of a method performed by a user equipment according to an embodiment of the present disclosure. The method may include steps 401 and 402.

[0137] Step 401: The UE decides whether a configuration of time window is reasonable.

[0138] The UE decides that a certain candidate cell satisfies the conditional event, but the time window has not yet started, that is, the time window is too late. At this time, the resources reserved by the candidate cell for the UE have not yet started, but at least the candidate cell has received the context information of the UE. Upon receiving a Handover Request message transmitted by the source base station, the candidate cell allocates for the UE a signaling radio bearer. The signaling radio bearer is a UE's dedicated control channel which can transfer RRC messages. The signaling radio bearer is operable when the time window has not yet started. The candidate cell may receive an RRC Reconfiguration Complete message from the UE's dedicated control channel. When the UE decides that the time window has not yet started, although the dedicated RACH resources are allocated by the candidate cell, the UE knows that the RACH resource has not yet started. The UE may initiate a contention-based random access process to synchronize with the candidate cell, and then transmit an RRC Reconfiguration Complete to the candidate cell. The RRC Reconfiguration Complete message contains a conditional reconfiguration identity. The candidate cell that receives the message may find the context of the corresponding UE from the conditional reconfiguration identity, and then activate or start the reserved resources in advance. If there are no reserved resources, then resources are allocated. Alternatively, the RRC Reconfiguration Complete message contains an identity of the old cell (or source cell or source serving cell) and / or a UE identity of the UE in the old cell, such as C-RNTI (Cell Radio Network Temporary Identity). The candidate cell may find the context information of the UE saved by the candidate cell from the cell identity and / or the old C-RNTI, and then activate or start the reserved resources in advance. If there are no reserved resources, then resources are allocated according to the UE's context.

[0139] If the UE decides that a certain candidate cell satisfies the conditional event, but the time window has expired, that is, the time window is too early, considering that the candidate cell may have released the UE's context information, the UE does not perform conditional handover, and proceeds to step 402 to transmit an RRC Setup Request message to the candidate cell to reset up the UE's context information and channel.

[0140] Alternatively, if the UE decides that a certain candidate cell satisfies the conditional event, but the time window has not yet started, that is, the time window is too late or has expired, considering that the candidate cell may not be able to receive the RRC Reconfiguration Complete message properly, or that the candidate cell has released the UE's context information, the UE does not perform conditional handover, and proceeds to step 402 to transmit an RRC Setup Request message to the candidate cell to reset up the UE's context information and channel.

[0141] The RRC Setup Request message may contain an identity of the old cell (or source cell or original serving cell) and / or a UE identity of the UE in the old cell, such as C-RNTI (Cell Radio Network Temporary Identity). After receiving an RRC Setup Request, the candidate cell transmits, to the old base station with the identity of the old cell, a Handover Success message or a UE Context Release Request message, which carries the identity of the old cell and / or the identity of the old UE. The old base station may delete, after receiving this message, the context of the UE corresponding to the UE identity.

[0142] Step 402: The UE transmits an RRC Reconfiguration Complete message or an RRC Setup message to the base station.

[0143] Through the above method, an RRC Reconfiguration Complete message can still be properly received in the case that the time window is set to be too late, or the UE can directly transmit an RRC Setup message to reset up an RRC connection in the case that the time window is set to be too early, which speeds up the RRC setup process, or the UE can directly transmit an RRC Setup message to reset up an RRC connection in the case that the time window is set to be too early or too late, which speeds up the RRC setup process.

[0144] Fig. 5 is a block diagram of a network device according to an embodiment of the present disclosure.

[0145] A network node in the network can be used to implement the first network device, the second network device, the source base station, the candidate base station, the base station 2 and the like in the present invention. Referring to Fig. 5, the network node according to the present invention includes a transceiver 510, a controller 520 and a memory 530. The transceiver 510, the controller 520 and the memory 530 are configured to perform the operations of the methods and / or embodiments of the present invention. Although the transceiver 510, the controller 520 and the memory 530 are shown as separate entities, they may be implemented as a single entity, such as a single chip. The transceiver 510, the controller 520 and the memory 530 may be electrically connected or coupled to each other. The transceiver 510 may transmit and receive signals to and from other network nodes, such as UE, MN, SN, S-SN, T-SN, other candidate T-SN or core network node. The controller 520 may include one or more processing units (e.g. processors), and may control the network device to perform the operations and / or functions according to one of the above embodiments. The memory 530 may store instructions for implementing the operations and / or functions of one of the above embodiments described.

[0146] Fig. 6 is a block diagram of a user equipment (UE) according to an embodiment of the present disclosure.

[0147] Referring to Fig. 6, the UE according to the present invention includes a transceiver 610, a controller 620 and a memory 630. The transceiver 610, the controller 620 and the memory 630 are configured to perform the operations of the methods and / or embodiments of the present invention. Although the transceiver 610, the controller 620 and the memory 630 are shown as separate entities, they may be implemented as a single entity, such as a single chip. The transceiver 610, the controller 620 and the memory 630 may be electrically connected or coupled to each other. The transceiver 610 may transmit and receive signals to and from other network nodes, such as UE, MN, SN, S-SN, T-SN, other candidate T-SN or core network node. The controller 620 may include one or more processing units (e.g. processors), and may control the UE to perform the operations and / or functions according to one of the above embodiments. The memory 630 may store instructions for implementing the operations and / or functions of one of the above embodiments described.

[0148] Those skilled in the art will understand that the illustrative embodiments described above are described herein and are not intended to be limiting. It should be understood that any two or more of the embodiments disclosed herein can be combined in any combination. In addition, other embodiments can be utilized and other changes can be made without departing from the spirit and scope of the subject matter presented herein. It will be readily understood that aspects of the present invention of the present disclosure, as generally described herein and shown in the accompanying drawings, can be arranged, substituted, combined, separated and designed in various different configurations, all of which are contemplated herein.

[0149] Those skilled in the art will understand that the various illustrative logical blocks, modules, circuits, and steps described in the present application can be implemented as hardware, software, or a combination of both. In order to clearly illustrate this interchangeability between hardware and software, various illustrative components, blocks, modules, circuits, and steps are generally described above in the form of their function set. Whether such a function set is implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system. Skilled people can implement the described function set in different ways for each specific application, but such design decisions should not be interpreted as causing a departure from the scope of the present application.

[0150] The various illustrative logic blocks, modules, and circuits described in the present application can be implemented in a general-purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic devices, discrete gate or transistor logic, discrete hardware component, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors cooperating with a DSP core, or any other such configuration.

[0151] The steps of the method or technique described in the present application can be embodied directly in hardware, in a software module executed by a processor, or in a combination of both. Software modules may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, register, hard disk, removable disk, or any other form of storage media known in the art. An exemplary storage medium is coupled to a processor to enable the processor to read and write information from / to the storage medium. In the alternative, the storage medium may be integrated into the processor. The processor and storage medium may reside in an ASIC. The ASIC may reside in the UE. In the alternative, the processor and the storage medium may reside in the UE as discrete components.

[0152] In one or more exemplary designs, the described functions can be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, each function can be stored on or transferred by a computer-readable medium as one or more instructions or codes. Computer-readable media include both computer storage media and communication media, which includes any media that facilitates the transfer of computer programs from one place to another. The storage medium may be any available medium that can be accessed by a general-purpose or special-purpose computer.

[0153] What has been described above is only an exemplary embodiment of the present disclosure, and is not used to limit the protection scope of the present disclosure, which is determined by the appended claims.

Claims

1.A method for communication by a first network device in a wireless communication system, comprising:receiving a first message including radio link failure (RLF) report related to a user equipment (UE) from a second network device, wherein the RLF report includes information related to a time of an RLF; andadjusting a setting of a time window related to a conditional handover (CHO) based on the information related to the time of the RLF.2.The method of claim 1, wherein the information related to the time of the RLF includes at least one of:first time indication information for indicating a duration from a time at which the time window starts to a time at which the RLF is detected;second time indication information for indicating a duration from a time at which the time window ends to the time at which the RLF is detected;third time indication information for indicating a duration from the time at which the RLF is detected to the time at which the time window starts;fourth time indication information for indicating a duration from the time at which the RLF is detected to the time at which the time window ends;fifth indication information for indicating whether the time window ends when the RLF occurs; andsixth indication information for indicating whether the time window starts when the RLF occurs;3.The method of claim 1, wherein the RLF report includes at least one of:seventh indication information for indicating that the time window ends or starts too early; andeighth indication information for indicating that the time window starts or ends too late.4.The method of claim 1, further comprising:transmitting, to at least one candidate base station, a handover request related to the CHO of the UE;receiving, from the at least one candidate base station, a handover request acknowledgement;transmitting, to the UE, a radio resource control (RRC) reconfiguration request information related to the CHO of the UE; andreceiving, from the UE, a RRC reconfiguration complete message.5.The method of claim 4, wherein the RLF is related to a failure of the CHO to the at least one candidate base station.6.A method for communication by a second network device in a wireless communication system, comprising:receiving a first message including radio link failure (RLF) report related to a user equipment from the UE, wherein the RLF report includes information related to a time of the RLF; andtransmitting a second message including the RLF report to a first network device.7.The method of claim 6, wherein the information related to the time of the RLF includes at least one of:first time indication information for indicating a duration from a time at which the time window starts to a time at which the RLF is detected;second time indication information for indicating a duration from a time at which the time window ends to the time at which the RLF is detected;third time indication information for indicating a duration from the time at which the RLF is detected to the time at which the time window starts;fourth time indication information for indicating a duration from the time at which the RLF is detected to the time at which the time window ends;fifth indication information for indicating whether the time window ends when the RLF occurs; andsixth indication information for indicating whether the time window starts when the RLF occurs;8.The method of claim 6, wherein the RLF report includes at least one of:seventh indication information for indicating that the time window ends or starts too early; andeighth indication information for indicating that the time window starts or ends too late.9.The method of claim 6, wherein the RLF is related to a failure of a conditional handover (CHO) of the UE.10.The method of claim 6, further comprising:establishing a radio resource control (RRC) connection with the UE;transmitting a UE information request to the UE; andreceiving a UE information response including the RLF report from the UE,wherein the first message is a UE information response.11.A first network device in a wireless communication system, comprising:a transceiver; andat least one processor coupled to the transceiver, wherein the at least one processor is configured to:receive a first message including radio link failure (RLF) report related to a user equipment (UE) from a second network device, wherein the RLF report includes information related to a time of an RLF; andadjust a setting of a time window related to a conditional handover (CHO) based on the information related to the time of the RLF.12.The first network device of claim 11, wherein the information related to the time of the RLF includes at least one of:first time indication information for indicating a duration from a time at which the time window starts to a time at which the RLF is detected;second time indication information for indicating a duration from a time at which the time window ends to the time at which the RLF is detected;third time indication information for indicating a duration from the time at which the RLF is detected to the time at which the time window starts;fourth time indication information for indicating a duration from the time at which the RLF is detected to the time at which the time window ends;fifth indication information for indicating whether the time window ends when the RLF occurs; andsixth indication information for indicating whether the time window starts when the RLF occurs;13.The first network device of claim 11, wherein the RLF report includes at least one of:seventh indication information for indicating that the time window ends or starts too early; andeighth indication information for indicating that the time window starts or ends too late.14.The first network device of claim 1, wherein the at last one processor is further configured to:transmit, to at least one candidate base station, a handover request related to the CHO of the UE;receive, from the at least one candidate base station, a handover request acknowledgement;transmit, to the UE, a radio resource control (RRC) reconfiguration request information related to the CHO of the UE; andreceive, from the UE, a RRC reconfiguration complete message.15.The first network device of claim 4, wherein the RLF is related to a failure of the CHO to the at least one candidate base station.

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