Radio link failure recovery method and user equipment

Abstract

The present disclosure provides a radio link failure recovery method and a user equipment. The radio link failure recovery method comprises: the user equipment UE initiates an RRC connection reestablishment process; in a cell selection process of the RRC connection reestablishment process, when the selected cell is a conditional switching candidate cell of the UE, the UE identifies the selected conditional switching candidate cell in a radio link failure report.

Description

Technical Field

[0001] The present disclosure relates to the technical field of wireless communications, and more specifically, to a recovery method after a wireless link failure and a user equipment. Background Art

[0002] In June 2018, a new research project for 5G technical standards was approved at the 3rd Generation Partnership Project (3GPP) RAN#80 plenary meeting (see non-patent document: RP-181433: New WID on NR (New Radio) mobility enhancements). In addition, there is another new research project for Release 16 (see non-patent document: RP-190272: WID for Even further Mobility enhancement in E-UTRAN (Evolved-Universal Terrestrail Radio Access Network)). One of the research objectives of these two projects is to find a solution to meet one of the mobility needs in the network: seamless switching, that is, to meet a switching interruption time of 0 milliseconds or close to 0 milliseconds during the cell switching process, and to enhance the robustness of the switching. Among the solutions being studied to reduce the switching interruption time and / or enhance the robustness of the switching, there is a solution called conditional handover (CHO). In the CHO mechanism, the base station sends a handover command to the UE in advance, and the handover command contains conditional configuration information. The UE saves the received conditional handover command, and performs handover according to the previously received handover command when the configured condition is met. In this way, the handover command reception success rate can be improved by sending the handover command in advance, thereby improving the handover success rate and avoiding the delay caused by the handover failure due to the handover command reception failure to interrupt the service.

[0003] The present disclosure proposes solutions to some problems of implementing CHO in NR systems and LTE (Long Term Evolution) systems. Summary of the invention

[0004] The purpose of the embodiments of the present disclosure is to propose a solution to the problem of implementing CHO technology in NR systems and LTE systems. More specifically, the present disclosure proposes a solution to the problem of how to use a saved CHO configuration to restore a link connection when a radio link fails, such as how to set a radio link failure report in a solution of using a saved CHO configuration to restore a link connection. The embodiments of the present disclosure provide a recovery method when a radio link fails in a user equipment and a corresponding user equipment.

[0005] According to the first aspect of the present disclosure, a wireless link failure recovery method is proposed, including: a user equipment UE initiates an RRC connection re-establishment process; during a cell selection process of the RRC connection re-establishment process, when the selected cell is a conditional switching candidate cell of the UE, the UE identifies the selected conditional switching candidate cell in a wireless link failure report.

[0006] In the radio link failure recovery method of the first aspect above, the UE may set the link recovery cell identifier in the radio link failure report variable VarRLF-Report to the selected conditional handover candidate cell identifier.

[0007] In the wireless link failure recovery method of the first aspect above, when the selected cell is a conditional switching candidate cell for the UE, the following operations can also be performed: the UE performs conditional switching to the selected cell, initiates a conditional switching process, applies the saved conditional switching configuration of the cell, and performs access to the selected cell.

[0008] In the radio link failure recovery method of the first aspect above, when the selected cell is not a conditional handover candidate cell for the UE, the RRC connection reestablishment process is continued.

[0009] According to a second aspect of the present disclosure, a radio link failure recovery method is provided, comprising: determining whether a radio link failure RLF occurs in a radio link of a user equipment UE; when the RLF occurs in the UE, if the UE is configured with conditional switching, the UE performs a cell selection process in a conditional switching link recovery process; in a case where the selected cell is a conditional switching candidate cell of the UE, the UE identifies the selected conditional switching candidate cell in a radio link failure report.

[0010] In the radio link failure recovery method of the second aspect, the UE may set the link recovery cell identifier in the radio link failure report variable VarRLF-Report to the selected conditional switching candidate cell identifier.

[0011] In the wireless link failure recovery method of the second aspect above, when the selected cell is a conditional switching candidate cell for the UE, the following operations may also be performed: Operation 1: the UE performs conditional switching to the selected cell, initiates a conditional switching process, applies the saved conditional switching configuration of the cell, and performs access to the selected cell; Operation 2: when available wireless link failure or switching failure information is saved in the wireless link failure report variable of the UE and the current public land mobile network PLMN of the UE is included in the PLMN identification list saved in the wireless link failure report variable, the UE includes indication information in the conditional switching completion message, and the indication information is used to indicate that there is available wireless link failure or switching failure related information saved on the UE.

[0012] In the radio link failure recovery method of the second aspect above, when the selected cell is not a conditional handover candidate cell for the UE, an RRC connection re-establishment process is initiated.

[0013] According to a third aspect of the present disclosure, a user equipment is provided, comprising: a processor; and a memory storing instructions; wherein the instructions, when executed by the processor, execute the radio link failure recovery method described in the context. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] For a more complete understanding of the present disclosure and its advantages, reference will now be made to the following description taken in conjunction with the accompanying drawings, in which:

[0015] Figure 1 It is a sequence diagram showing how a connected user equipment UE changes a serving cell through a handover procedure.

[0016] Figure 2 This is a schematic diagram showing the flow of condition switching.

[0017] Figure 3 The invention is a flowchart showing radio link recovery based on conditional switching when a radio link fails.

[0018] Figure 4 It is a block diagram showing a user equipment UE involved in the present invention.

[0019] In the drawings, the same or similar structures are marked with the same or similar reference numerals. DETAILED DESCRIPTION

[0020] Other aspects, advantages and salient features of the disclosure will become apparent to those skilled in the art from the following detailed description of exemplary embodiments of the disclosure taken in conjunction with the accompanying drawings.

[0021] In this disclosure, the terms "include" and "including" and their derivatives mean inclusion without limitation; the term "or" is inclusive, meaning and / or.

[0022] In this specification, the various embodiments described below for describing the principles of the present disclosure are merely illustrative and should not be interpreted in any way as limiting the scope of the disclosure. The following description with reference to the accompanying drawings is used to help fully understand the exemplary embodiments of the present disclosure as defined by the claims and their equivalents. The following description includes a variety of specific details to aid understanding, but these details should be considered merely exemplary. Therefore, it should be recognized by those of ordinary skill in the art that various changes and modifications may be made to the embodiments described herein without departing from the scope and spirit of the present disclosure. In addition, for the sake of clarity and brevity, descriptions of well-known functions and structures are omitted. In addition, throughout the accompanying drawings, the same reference numerals are used for similar functions and operations.

[0023] The following uses the Long Term Evolution (LTE) / NR mobile communication system and its subsequent evolution versions as example application environments to specifically describe multiple implementations according to the present disclosure. However, it should be noted that the present disclosure is not limited to the following implementations, but is applicable to more other wireless communication systems. Unless otherwise specified, in the present disclosure, the concepts of cell and base station can be interchangeable; the LTE system is also used to refer to 5G and subsequent LTE systems (such as eLTE systems, or LTE systems that can be connected to the 5G core network), and LTE can be replaced by Evolved Universal Terrestrial Radio Access (E-UTRA) or Evolved Universal Terrestrial Radio Access Network E-UTRAN. In the present disclosure, handover refers to the change of the primary cell initiated by the network side, including the primary cell change between cells and the primary cell change within the cell, that is, the primary cell of the UE is changed from the source cell to the target cell, wherein the source cell and the target cell can be the same cell or different cells, and in this process, the key or security algorithm used for access layer security can also be updated accordingly. The source cell is also called the source base station, and may also be the source beam or the source transmission point (Transmission point, TRP). The target cell may also be called the target base station, and may also be the target beam or the target transmission point. The source cell refers to the cell serving the UE to which the UE is connected before the switching process is initiated, that is, the cell from which the UE receives the RRC message containing the switching command. The target cell refers to the cell serving the UE to which the UE is connected after the switching process is successfully completed, or the cell indicated by the target cell identifier contained in the switching command, and the cell to which the UE accesses when receiving the switching execution command. The switching command described in the present disclosure is used to trigger the UE to perform a switching. In the NR system, it is an RRC reconfiguration message containing a synchronous reconfiguration (Reconfiguration with sync) information element, and further, it is an RRC reconfiguration message containing a synchronous reconfiguration (Reconfiguration with sync) information element for the master cell group (Master Cell Group, MCG). At this time, the switching can also be referred to as the synchronous reconfiguration of the MCG. In the LTE system, it is an RRC connection reconfiguration message containing a mobility control information (Mobility Control Information) information element. Among them, the synchronous reconfiguration information element or the mobile control information information element includes configuration information of the target cell, such as the target cell identifier, the target cell frequency, the public configuration of the target cell such as system information, the random access configuration used by the UE to access the target cell, the security parameter configuration of the UE in the target cell, the wireless bearer configuration of the UE in the target cell, etc.For ease of description, in the present disclosure, the RRC reconfiguration message is equivalent to the RRC connection reconfiguration message; similarly, its response message RRC reconfiguration completion message is equivalent to the RRC connection reconfiguration completion message. The RRC connection reestablishment request message is equivalent to the RRC reestablishment request message, and the RRC reestablishment message is equivalent to the RRC connection reestablishment message; similarly, its response message RRC reestablishment completion message is equivalent to the RRC connection reestablishment completion message. The handover command is equivalent to the RRC message containing the handover command, which refers to the RRC message or the configuration in the RRC message that triggers the UE to perform the handover. The handover configuration refers to all or part of the configuration in the handover command. Cancellation, release, deletion, clearing and clearing can be replaced. Execution, use and application can be replaced. Configuration and reconfiguration can be replaced. Link and connection can be replaced. Monitoring (monitor) and detection (detect) can be replaced. Conditional handover command and conditional handover configuration are replaceable.

[0024] In the present application, after receiving a Radio Resource Control (RRC) message including a handover command, the UE can still maintain communication with the source base station including data transmission before initiating the handover process, so as to further reduce the time of data transmission interruption.

[0025] The following briefly describes the prior art involved in the embodiments of the present disclosure.

[0026] The general switching process in the existing mechanism:

[0027] The user mobility in the connected state is mainly achieved through a handover process, and the handover refers to the process of changing the serving cell of the UE in the RRC connected state. Figure 1 is a sequence diagram showing how a connected user equipment UE changes its serving cell through a handover process. Figure 1 As shown in FIG. 1 , the switching process generally includes the following stages:

[0028] Phase 1: Measurement phase. The base station sends measurement configuration to the user equipment (UE); the UE measures the radio link corresponding to the serving cell or neighboring cell based on the measurement configuration. When the configured measurement reporting conditions are met, the UE sends a measurement report to the base station. The measurement phase is not mandatory, and the base station can also blindly switch the UE when there is no valid measurement report.

[0029] Phase 2: Handover preparation phase. The base station decides whether to trigger a handover for the UE based on the received measurement report and other factors such as the base station load. If it is determined that a handover is triggered for the UE, the source base station initiates the handover preparation process by sending a handover request message to the target base station. The target base station decides whether to accept the handover request for the UE based on factors such as the UE context in the handover request message and the available resources of the target base station. If yes, it replies to the source base station with a handover confirmation message, which contains an inter-node RRC message, namely the handover command.

[0030] Phase 3: Handover execution phase. The source base station sends the handover command to the UE and starts forwarding the UE's data to the target base station. The UE that receives the handover command immediately applies the configuration of the handover command to perform the handover, accesses the target base station through the random access process, and sends a confirmation message to the target base station. The random access process is not mandatory.

[0031] Phase 4: Handover completion phase. After the target base station confirms that the UE has successfully accessed, it sends a handover completion message to the source base station. The source base station can release the UE context stored thereon.

[0032] As can be seen from the above, the handover process in the current system will cause interruption of data transmission. In the Release 14 version of the LTE system, the optimization of the handover process, such as handover without random access process and Make Before Break (MBB), is aimed at reducing the data interruption time during the handover process.

[0033] Condition-based switching:

[0034] Next, we will briefly describe conditional switching. As mentioned above, in the Release 16 technical requirements, it is required to meet the "0ms" data interruption delay as much as possible during the mobile switching process, and to improve the robustness of the switching to achieve the mobility requirements of seamless switching in NR. In the current switching process, one reason for the failure of the switching and the interruption of data transmission for a long time is the failure to receive the switching command due to the untimely issuance of the switching command. For this problem, a feasible method is conditional switching (referred to as conditional switching). Figure 2It is a schematic diagram showing the process of conditional switching. In conditional switching, a relatively conservative measurement report threshold is set so that the base station obtains the measurement results in advance, and performs switching preparation in advance according to the measurement results and the selected target base station, so that the base station can send a switching command containing the candidate cell for switching and the switching execution condition to the UE in advance before the real switching condition (relative to the conservative measurement report threshold) is met, which carries the conditions for the UE to perform the switching. Different from the existing switching mechanism of LTE, after receiving the conditional switching command, the UE does not perform the switching immediately, but saves the received switching command configuration, and starts monitoring the link quality of the source cell or the link quality of the target cell according to the switching execution condition carried in the switching command message to evaluate whether the switching execution condition is met. Only when it is monitored that the configured switching execution condition is met, the UE starts to execute the saved switching command and access the target cell. During the switching process, the UE will stop evaluating the configured switching execution condition. In short, conditional switching refers to a switching process that is only executed when one or more configured switching execution conditions are met. For the handover execution condition, for example, the handover execution condition is a measurement event, such as the condition is measurement event A3 (the signal quality of the neighboring cell is better than that of the serving cell by an offset for a period of time). The neighboring cell corresponds to the target cell of the handover. Generally speaking, all measurement events defined in the current 3GPP standard specifications 36.331 and 38.331 (see section 5.5.4), such as A1 to A5, can be included in the conditional handover command as handover execution conditions.

[0035] Link recovery mechanism in existing mechanisms:

[0036] Again, let's introduce the link recovery mechanism in the existing mechanism. In the existing mechanism, when RLF of the main cell group occurs or the UE fails to perform the handover process (HandOver Failure, HOF) (i.e., T304 times out), the UE will initiate an RRC connection re-establishment process to rebuild / restore the connection with the network side. In the initiated RRC connection re-establishment process, the UE first performs a cell selection process to select a re-established cell, and sends an RRC connection re-establishment request message to it. When the UE receives a response message as an RRC connection re-establishment message, the UE re-establishes the RRC connection according to the configuration in the RRC connection re-establishment message, and feeds back an RRC connection re-establishment completion message to the base station, successfully ending the RRC connection re-establishment process. The re-established cell refers to the cell used by the UE to send an RRC connection re-establishment request message and receive a corresponding response message for re-establishing the RRC connection in the RRC connected state. A timer T311 is defined in the RRC re-establishment process. T311 is started when the UE initiates the RRC connection re-establishment process. When a suitable cell for reconstruction is selected during the cell selection process, T311 is stopped; if T311 times out and the UE is unable to select a suitable cell, it is generally considered that the UE is out of coverage. The UE will leave the RRC connected state and enter the RRC idle state or RRC inactive state (RRC_Inactive).

[0037] Link failure reporting mechanism in the existing mechanism:

[0038] In the current LTE system, the UE will generate and save a radio link failure report (RLF report) when a link failure or handover failure occurs. For example, the UE variable used to save the radio link failure report is VarRLF-Report. After restoring the connection with the network side (such as through the RRC reestablishment process or the RRC establishment process), the UE can inform the network side through an RRC message that there is an available radio link failure report (indicated by the rlf-InfoAvailable information element). For example, the UE can inform the network side that the UE has a saved and available radio link failure report in the RRC connection reestablishment complete message (RRCConnectionReestablishmentComplete) during the RRC connection reestablishment process, the RRC connection reconfiguration complete message (RRCConnectionReconfigurationComplete) during the RRC connection reconfiguration process, the RRC connection setup complete message (RRCConnectionSetupComplete) during the RRC connection establishment process, or the RRC connection recovery complete message (RRCConnectionResumeComplete) during the RRC connection recovery process. After receiving the indication, the network side can request the UE to report its saved radio link failure report through an RRC message (the rlf-ReportReq information element in the UEInformationRequest message indicates the request). The UE will report the saved radio link failure report (the rlf-Report information element in the UEInformationResponse message indicates the request) to the network side in the response RRC message. The radio link failure report obtained by the network side is used for network optimization, such as network coverage and mobility robustness optimization. The radio link failure report may include: measurement results of the source cell and neighbor cells available at the time of link failure, location information, the main cell identifier where the link failure occurred, the link failure type (RLF or HOF), the reason for RLF, the time from connection failure to reporting of the radio link failure, the time from the last switch to the connection failure, etc. In addition, the RRC re-establishment cell identifier in the radio link failure report can provide additional auxiliary information for the network side. For example, if the RRC re-establishment cell information in the wireless link failure report does not exist, the network side may assume that the UE did not find any suitable cell during the wireless link recovery process after the link failure, that is, the RRC connection re-establishment process, and the UE may be in a network coverage hole when the wireless link failure occurs; if the RRC re-establishment cell identifier in the wireless link failure report is not the source cell where the UE was located when the failure occurred, the network side may assume that the UE failure was not due to premature switching.The above RRC re-establishment cell identifier is the identifier of the RRC re-establishment cell that the UE attempts to re-establish the RRC connection, and includes it in the radio link failure report after triggering the RRC connection re-establishment request message during the RRC connection re-establishment process.

[0039] Radio link recovery using saved conditional handoff configuration:

[0040] After the conditional switching is configured, the UE will not perform the switching immediately, but will perform the switching according to the received or saved conditional switching configuration after the corresponding conditions are met. During the period from the moment the UE receives the conditional switching configuration to the moment the switching is performed according to the received conditional switching configuration, the UE still maintains communication with the source base station. During this period, a radio link failure (RLF) may occur between the UE and the source base station. At the 106th meeting of the 3GPP RAN2 Working Group, a conclusion was reached on the situation where the switching execution conditions of the above-mentioned conditional switching are not met and RLF occurs: when RLF occurs, the UE first selects a cell to perform link recovery. If the selected cell is a conditional switching candidate cell, the UE performs the switching to the cell according to the conditional switching configuration corresponding to the cell; if the selected cell is not a conditional switching candidate cell, the UE attempts to restore the connection with the network side by sending an RRC connection establishment request to the selected cell. This enhancement of the link recovery mechanism is referred to in the present disclosure as a link failure recovery mechanism based on conditional switching configuration (for convenience of description, referred to as a conditional switching link recovery mechanism). The conditional handover candidate cell refers to the (target) cell in the conditional handover configuration in the RRC message received by the UE for configuring the conditional handover, that is, the cell identified by the cell identifier in the synchronous reconfiguration information element (ReconfigurationWithSync) or the mobility control information element (MobilityControlInfo). The network side can configure one or more handover execution conditional candidate cells for the UE at the same time.

[0041] The cell selection process may refer to 3GPP protocol specification 38.304 or 36.304. If the cell selected by the cell selection process is a cell of a different radio access technology (i.e., an Inter-RAT cell), the UE performs an operation of entering the RRC idle state, and the RRC release reason is RRC connection failure. The operation of entering the RRC idle state may refer to section 5.3.11 of protocol specification 38.331.

[0042] As mentioned above, the UE includes the re-established cell identifier in the wireless link failure report only after triggering the RRC connection re-establishment request message when attempting the RRC connection re-establishment process to the network side. However, in the conditional switching link recovery mechanism, the existing mechanism cannot achieve this function, which is the problem that the present disclosure focuses on. The present disclosure proposes a solution to the problem of how to set up a wireless link failure report in the conditional switching link recovery mechanism when the wireless link fails. Through the method described in the present disclosure, the UE can include the cell identifier of the attempted connection recovery in the wireless link failure report and report it to the network side, thereby providing more auxiliary information for the network side to optimize the mobile performance.

[0043] The following are several embodiments of the present disclosure executed on the UE based on the above-mentioned problems. In the following embodiments, the UE is configured with conditional switching, which includes the UE receiving an RRC message containing a conditional switching command from a base station, saving the switching configuration in the switching command, and monitoring whether the switching execution condition is met according to the switching execution condition. The switching configuration refers to the RRC configuration generated by the UE according to the configuration in the switching command. Optionally, the switching configuration refers to the RRC configuration generated by the UE according to the configuration in the switching command and / or the RRC configuration of the current UE. The switching execution condition, that is, the UE will only perform the switching when the condition is met, and the switching configuration is applied, and the switching execution condition is included in the conditional switching command.

[0044] Example 1

[0045] This embodiment provides a method for setting a cell identifier in a radio link failure report in a conditional handover link recovery mechanism when a radio link fails. When a UE uses the conditional handover link recovery mechanism to perform link recovery, the network side can obtain the cell identifier of the UE attempting to connect to recovery from the radio link failure report reported by the UE, thereby locating the network problem more accurately and optimizing network configuration parameters such as handover threshold parameters. Figure 3 is a flow chart showing wireless link recovery based on conditional switching when a wireless link fails, such as Figure 3 As shown, the wireless link recovery using the conditional switching link recovery mechanism includes the following steps.

[0046] Step 1: UE initiates the RRC connection re-establishment process.

[0047] Step 2: During the cell selection process in the RRC connection reestablishment process, when a suitable cell is selected, if the selected cell is a conditional switching candidate cell for the UE, execute step 3A; otherwise, if the selected cell is not a conditional switching candidate cell for the UE, execute step 3B.

[0048] In the NR system, the selected suitable cell is an NR cell; in the LTE system, the selected suitable cell is an LTE / E-UTRAN cell.

[0049] Step 3A: The UE performs the following operations:

[0050] Operation 1: The UE identifies the selected conditional handover candidate cell in the radio link failure report. For example, the UE sets a cell identification information element in the saved radio link failure report variable (VarRLF-Report) as the cell identification of the selected conditional handover candidate cell. The cell identification can be a global cell identification that uniquely identifies a cell globally in a wireless communication system, or it can be a physical cell identification or the frequency where the cell is located. In the LTE system, the global cell identification is the Evolved Cell Global Identifier (ECGI), which is used to uniquely identify the cell in the LTE system.

[0051] The information element used to carry the cell identifier can reuse the reestablishment cell identifier information element (reestablishmentCellid) in the existing mechanism, or it can be a newly defined information element different from the reestablishment cell identifier information element, such as a conditional handover cell identifier (such as expressed as a conditionalHOcellid information element), or a link recovery cell identifier (linkrecoverycellid or connectionrecoverycellid, recoverycellid information element). The cell identifier is used to indicate the cell in which the UE performs a recovery attempt (conditional handover) during the recovery process after a radio link failure. Its name is not limited in this disclosure.

[0052] Operation 2: The UE performs conditional handover to the selected cell, initiates a conditional handover process, applies the saved conditional handover configuration of the cell, and performs access to the selected cell.

[0053] In one manner, the operation 1 is performed before the operation 2, that is, after the UE determines that the appropriate cell selected in the cell selection process in step 2 is a conditional handover candidate cell, the operation 1 is performed. In another manner, the operation 1 is completed after the operation 2 or during the execution of the operation 2, such as the UE performs the operation 1 in the initialization phase of initiating the conditional handover in the operation 2.

[0054] Step 3B: Continue the RRC connection re-establishment process, such as initiating the sending of an RRC connection re-establishment request message.

[0055] Optionally, as described above, the UE determines whether the selected cell is a conditional handover candidate cell of the UE, and the judgment is performed when the UE is configured with conditional handover and / or the reason for initiating the RRC connection re-establishment process is that the RLF of the MCG is monitored or the handover failure (that is, the timer (such as T304) used to detect the handover process has timed out, which also includes the conditional handover failure). Optionally, the UE determines whether the selected cell is a conditional handover candidate cell of the UE when the UE is enabled with the conditional handover link recovery mechanism.

[0056] In this step, the UE being configured with conditional switching is equivalent to the UE having a saved conditional switching configuration.

[0057] The selected cell is a conditional switching candidate cell and can also be described as the selected cell being included in the saved conditional switching configuration, preferably, included in the synchronous reconfiguration information element (ReconfigurationWithSync) or the mobile control information information element in the saved conditional switching configuration. The UE performs switching to the selected cell, that is, performs switching to the cell (or synchronous reconfiguration) according to the saved conditional switching configuration corresponding to the cell. In this operation, the UE can perform switching to the cell and restore communication with the network side as soon as possible without waiting for the conditions corresponding to the conditional switching candidate cell to be met. The operation of performing conditional switching includes one or more of the following: starting timer T304; executing the target cell RRC configuration in the conditional switching configuration corresponding to the target cell; executing the configuration in the synchronous reconfiguration information element corresponding to the target cell; downlink synchronization to the target cell; performing random access to the target cell; generating an RRC reconfiguration completion message and submitting it to the lower layer for sending.

[0058] Example 2

[0059] This embodiment provides another method for setting the re-established cell identifier in the radio link failure report in the conditional switching link recovery mechanism when the radio link fails. When the UE uses the conditional switching link recovery mechanism to perform link recovery, the network side can obtain the cell identifier of the UE attempting to connect to recovery from the radio link failure report reported by the UE, thereby locating the network problem more accurately to optimize network configuration parameters such as switching threshold parameters. Different from Example 1, the conditional switching recovery mechanism is not executed during the RRC connection re-establishment process, but when the UE configured with conditional switching occurs RLF, it first performs a cell selection process. If the selected cell is a conditional switching candidate cell, the UE performs a switch to the cell according to the conditional switching configuration corresponding to the cell; if the selected cell is not a conditional switching candidate cell, the UE initiates the RRC connection re-establishment process.

[0060] Step 1: RLF occurs in the radio link of the UE. More specifically, RLF occurs in the MCG link. Or a handover failure (HOF) occurs in the UE. The handover failure can be determined based on the timeout of a timer used to monitor the handover process, such as T304 timeout. The handover includes conditional handover. The handover failure also includes a conditional handover process failure.

[0061] Step 2: If the UE is configured with conditional handover, the UE performs a conditional handover link recovery process, which includes performing a cell selection process. The cell selection process is performed in accordance with the cell selection process in standard protocol specifications 38.304 or 36.304. The execution condition of step 2 also includes that the UE is enabled with the conditional handover link recovery mechanism.

[0062] The UE being configured with conditional switching is equivalent to the UE having a saved conditional switching configuration.

[0063] Step 3: The cell selection process of step 2 selects a suitable cell. When a suitable cell is selected, if the selected cell is a conditional handover candidate cell of the UE, step 4A is executed; otherwise, if the selected cell is not a conditional handover candidate cell of the UE, step 4B is executed.

[0064] In the NR system, the selected suitable cell is an NR cell; in the LTE system, the selected suitable cell is an LTE / E-UTRAN cell.

[0065] Step 4A: The UE performs the following operations:

[0066] Operation 1: The UE sets a cell identity information element in the saved radio link failure report variable (VarRLF-Report) as the cell identity of the selected conditional handover candidate cell. The cell identity may be a global cell identity that uniquely identifies a cell globally in a wireless communication system, or may be a physical cell identity or the frequency where the cell is located. In the LTE system, the global cell identity is the Evolved Cell Global Identifier (ECGI), which is used to uniquely identify the cell in the LTE system.

[0067] The information element used to carry the cell identifier can reuse the reestablishment cell identifier information element (reestablishmentCellid) in the existing mechanism, or it can be a newly defined information element different from the reestablishment cell identifier information element, such as a conditional handover cell identifier (such as expressed as a conditionalHOcellid information element), or a link recovery cell identifier (linkrecoverycellid or connectionrecoverycellid, recoverycellid information element). The cell identifier is used to indicate the cell in which the UE performs a recovery attempt (conditional handover) during the link recovery process after a radio link failure or a handover failure. Its name is not limited in this disclosure.

[0068] Operation 2: The UE performs conditional handover to the selected cell, initiates a conditional handover process, applies the saved conditional handover configuration of the cell, and performs access to the selected cell.

[0069] In one manner, the operation 1 is performed before the operation 2, that is, after the UE determines that the appropriate cell selected in the cell selection process in step 2 is a conditional handover candidate cell, the operation 1 is performed. In another manner, the operation 1 is completed after the operation 2 or during the execution of the operation 2, such as the UE performs the operation 1 in the initialization phase of initiating the conditional handover in the operation 2.

[0070] Step 4B: Initiate an RRC connection re-establishment procedure.

[0071] Optionally, as described above, the UE determines whether the selected cell is a conditional handover candidate cell of the UE, and the judgment is performed when the UE is configured with conditional handover and / or the reason for initiating the RRC connection re-establishment process is that the RLF of the MCG is monitored or the handover failure (that is, the timer (such as T304) used to detect the handover process has timed out, which also includes the conditional handover failure). Optionally, the UE determines whether the selected cell is a conditional handover candidate cell of the UE when the UE is enabled with the conditional handover link recovery mechanism.

[0072] The selected cell is a conditional switching candidate cell and can also be described as the selected cell being included in the saved conditional switching configuration, preferably, included in the synchronous reconfiguration information element (ReconfigurationWithSync) or the mobile control information information element in the saved conditional switching configuration. The UE performs switching to the selected cell, that is, performs switching to the cell (or synchronous reconfiguration) according to the saved conditional switching configuration corresponding to the cell. In this operation, the UE can perform switching to the cell and restore communication with the network side as soon as possible without waiting for the conditions corresponding to the conditional switching candidate cell to be met. The operation of performing conditional switching includes one or more of the following: starting timer T304; executing the target cell RRC configuration in the conditional switching configuration corresponding to the target cell; executing the configuration in the synchronous reconfiguration information element corresponding to the target cell; downlink synchronization to the target cell; performing random access to the target cell; generating an RRC reconfiguration completion message and submitting it to the lower layer for sending.

[0073] In the above embodiments 1 to 2, before the UE executes the conditional switching process or during the process, if a radio link failure or a switching failure process occurs before (just before) the execution of the conditional switching process, that is, the execution of the conditional switching process is triggered to restore the link connection when the link fails, then the UE will include an indication information for indicating the conditional switching target cell identifier in the saved radio link failure report to inform the network side that the UE has executed conditional switching in the cell corresponding to the cell identifier to restore the connection.

[0074] Example 3

[0075] This embodiment provides a method for a UE to report a radio link failure to a network, which is performed when the UE is configured with conditional switching.

[0076] Step 1: The UE initiates a conditional handover and accesses the selected conditional handover candidate cell.

[0077] The UE initiates the conditional handover when the conditional handover execution condition monitored by the UE is satisfied. The process of the UE accessing the selected conditional handover candidate cell is as described above and will not be repeated here.

[0078] Step 2: If the UE's radio link failure report variable stores available radio link failure or handover failure information and the UE's current public land mobile network (PLMN) is included in the PLMN identifier list stored in the radio link failure report variable, the UE includes an indication information in the conditional handover complete message. The indication information is used to indicate that the UE has available radio link failure or handover failure related information stored, and preferably, the UE's current PLMN is the UE's currently registered PLMN (RPLMN).

[0079] Example 4

[0080] This embodiment illustrates the user equipment disclosed in the present invention. Figure 4 is a block diagram showing a user equipment UE involved in the present invention. Figure 4 As shown, the user equipment UE40 includes a processor 401 and a memory 402. The processor 401 may include, for example, a microprocessor, a microcontroller, an embedded processor, etc. The memory 402 may include, for example, a volatile memory (such as a random access memory RAM), a hard disk drive (HDD), a non-volatile memory (such as a flash memory), or other memories, etc. The memory 402 stores program instructions. When the instructions are executed by the processor 401, the above-mentioned radio link recovery method described in detail in the present invention may be executed.

[0081] In the present disclosure, some different embodiments may work together.

[0082] In this disclosure, "base station" refers to a mobile communication data and control exchange center with large transmission power and wide coverage area, including functions such as resource allocation scheduling, data reception and transmission, etc. "User equipment" refers to a user mobile terminal, such as a mobile phone, a notebook, etc., which can communicate wirelessly with a base station or a micro base station.

[0083] The method of the present invention and the equipment involved have been described above in conjunction with the preferred embodiments. It will be appreciated by those skilled in the art that the method shown above is exemplary only. The method of the present invention is not limited to the steps and sequence shown above. The base station and user equipment shown above may include more modules, for example, modules that can be developed or developed in the future and can be used for base stations, MMEs, or UEs, etc. The various identifiers shown above are exemplary only and not restrictive, and the present invention is not limited to the specific information elements used as examples of these identifiers. Those skilled in the art may make many changes and modifications based on the teachings of the illustrated embodiments.

[0084] The program running on the device according to the present disclosure may be a program that enables a computer to implement the functions of the embodiments of the present disclosure by controlling a central processing unit (CPU). The program or information processed by the program may be temporarily stored in a volatile memory (such as a random access memory RAM), a hard disk drive (HDD), a non-volatile memory (such as a flash memory), or other memory systems.

[0085] The program for realizing the functions of each embodiment of the present disclosure can be recorded on a computer-readable recording medium. The corresponding functions can be realized by making a computer system read the program recorded on the recording medium and executing these programs. The so-called "computer system" herein can be a computer system embedded in the device, and can include an operating system or hardware (such as a peripheral device). "Computer-readable recording medium" can be a semiconductor recording medium, an optical recording medium, a magnetic recording medium, a recording medium of a short-term dynamic storage program, or any other recording medium readable by a computer.

[0086] The various features or functional modules of the devices used in the above embodiments can be implemented or executed by circuits (e.g., monolithic or multi-chip integrated circuits). Circuits designed to perform the functions described in this specification may include general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic, discrete hardware components, or any combination of the above devices. The general-purpose processor may be a microprocessor, or any existing processor, controller, microcontroller, or state machine. The above circuits may be digital circuits or analog circuits. In the case where new integrated circuit technologies have emerged to replace existing integrated circuits due to advances in semiconductor technology, one or more embodiments of the present disclosure may also be implemented using these new integrated circuit technologies.

[0087] In addition, the present disclosure is not limited to the above-mentioned embodiments. Although various examples of the embodiments have been described, the present disclosure is not limited thereto. Fixed or non-mobile electronic devices installed indoors or outdoors can be used as terminal devices or communication devices, such as AV equipment, kitchen equipment, cleaning equipment, air conditioners, office equipment, vending machines, and other household appliances.

[0088] As mentioned above, the embodiments of the present disclosure have been described in detail with reference to the accompanying drawings. However, the specific structure is not limited to the above embodiments, and the present disclosure also includes any design changes that do not deviate from the main purpose of the present disclosure. In addition, various changes can be made to the present disclosure within the scope of the claims, and the embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure. In addition, the components with the same effect described in the above embodiments can be replaced by each other.

Claims

1. A user equipment UE, comprising a processing unit and a memory, wherein: The memory stores a conditional switching configuration, and The processing unit is configured to: The RRC re-establishment procedure is initiated based on the following: The RRC re-establishment is triggered by detecting a radio link failure RLF of a master cell group MCG or a synchronization reconfiguration failure of the MCG; enabling link recovery based on conditional handover configuration; and The cell selected in the cell selection process in the RRC re-establishment is a conditional handover candidate cell in the synchronous reconfiguration included in the stored conditional handover configuration; Set the information element in the RLF variable VarRLF-report to the cell identity of the selected cell, and The stored conditional handover configuration associated with the selected cell is applied.

2. A method performed by a UE, the UE comprising a memory storing a conditional handover configuration, the method comprising: The RRC re-establishment procedure is initiated based on the following: The RRC re-establishment is triggered by detecting a radio link failure RLF of a master cell group MCG or a synchronization reconfiguration failure of the MCG; enabling link recovery based on conditional handover configuration; and The cell selected in the cell selection process in the RRC re-establishment is a conditional handover candidate cell in the synchronous reconfiguration included in the stored conditional handover configuration; Set the information element in the RLF variable VarRLF-report to the cell identity of the selected cell, and The stored conditional handover configuration associated with the selected cell is applied.

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