Wireless Link Failure Reporting Method and User Equipment

Abstract

The present disclosure provides a method for reporting radio link failure and a user equipment. The method for reporting radio link failure includes: a user equipment (UE) experiences a radio link failure (RLF) of a master cell group (MCG); the UE initiates a fast MCG link recovery process to restore the connection with the network side; the UE sends a radio link failure report to the network side, and the radio link failure report includes first fast MCG link recovery information, where the first fast MCG link recovery information is used to indicate that the UE has attempted a fast MCG link recovery mechanism based on the fast MCG link recovery process after the radio link failure corresponding to the radio link failure report.

Description

Technical Field

[0001] The present disclosure relates to the field of wireless communication technologies. More specifically, the present disclosure relates to a method for recovery after a radio link failure and a corresponding user equipment. Background Art

[0002] In June 2018, a new research project of a 5G technology standard was approved at the 80th plenary session of the 3rd Generation Partnership Project (3GPP) RAN (see non-patent literature: RP-181433: New WID on NR (New Radio) mobility enhancements). In addition, there is another new research project of Release 16 (see non-patent literature: 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 requirements in the network: seamless handover, that is, to be able to meet a handover interruption time of 0 milliseconds or close to 0 milliseconds during the cell handover process and enhance the robustness of the handover. Among the solutions being studied to reduce the handover interruption time and / or enhance the handover robustness, there is a solution called Conditional HandOver (CHO). In the CHO mechanism, the base station sends a handover command to the UE (User Equipment) in advance, and the handover command contains the configuration of handover execution conditions. The UE executes the handover according to the previously received and saved handover command only when the configured handover execution conditions are met. In this way, by sending the handover command in advance, the success rate of receiving the handover command can be improved, thereby improving the handover success rate and avoiding the delay caused by service interruption due to handover failure caused by the failure to receive the handover command.

[0003] In addition, the 3GPP RAN2 working group introduced a fast MCG (Master Cell Group) link recovery mechanism in Release 16. The fast MCG link recovery mechanism is relative to the existing link recovery mechanism (i.e., recovering the link connection through the RRC connection re-establishment process). In the fast MCG link recovery mechanism, when an RLF (Radio Link Failure) occurs in the MCG of a UE, if the link quality of the secondary cell group (SCG) of the UE is good, the UE initiates an MCG failure information procedure, and reports the information of the MCG link failure to the master base station through the SCG link, rather than directly triggering the RRC connection re-establishment process. The master base station that receives the MCG link failure information report can send an RRC connection reconfiguration message to the UE to trigger the UE to switch to a new cell or send an RRC release message to release the connection of the UE.

[0004] The present disclosure proposes a solution to the link failure reporting problem in the case of configuring the fast MCG link recovery mechanism or CHO in the NR system and the LTE (Long Term Evolution) system. Summary of the Invention

[0005] The purpose of the embodiments of the present disclosure is to propose a solution to the problem of wireless link failure reporting when the fast MCG link recovery mechanism or CHO is configured in the NR system and the LTE system. More specifically, the present disclosure proposes a solution to the problem of how to set relevant link recovery information in the wireless link failure report in the case of executing the fast MCG link recovery mechanism or the CHO recovery mechanism to recover the link. The embodiments of the present disclosure provide a wireless link failure reporting method executed in a user equipment and the corresponding user equipment.

[0006] According to a first aspect of the present disclosure, a wireless link failure reporting method is proposed, including: a user equipment (UE) experiences a radio link failure (RLF) of a master cell group (MCG); the UE initiates a fast MCG link recovery process to recover the connection with the network side; the UE sends a wireless link failure report to the network side, and the wireless link failure report includes first fast MCG link recovery information, and the first fast MCG link recovery information is used to indicate that the UE has attempted the fast MCG link recovery mechanism based on the fast MCG link recovery process after the wireless link failure corresponding to the wireless link failure report.

[0007] In the wireless link failure reporting method of the above first aspect, the wireless link failure report may further include at least one of the second fast MCG link recovery information and the third fast MCG link recovery information. Among them, the second fast MCG link recovery information may be used to indicate that: in the fast MCG link recovery mechanism, after the UE sends an RRC message to the network side, it receives a response RRC message from the network side. The third fast MCG link recovery information may be used to indicate that: in the fast MCG link recovery mechanism, after the UE sends an RRC message to the network side, it receives the cell identifier of the target handover cell included in the RRC reconfiguration RRCreconfiguration message.

[0008] In the wireless link failure reporting method of the above first aspect, the wireless link failure report may further include the fourth fast MCG link recovery information. The fourth fast MCG link recovery information may be used to indicate that: in the fast MCG link recovery mechanism, after the UE sends an RRC message to the network side, it does not receive a response RRC message from the network side.

[0009] In the wireless link failure reporting method of the above first aspect, the RRC message may include MCG failure information MCGfailureinformation.

[0010] In the wireless link failure reporting method of the above first aspect, the response RRC message may include: an RRC reconfiguration RRCreconfiguration message for instructing the UE to perform handover, or an RRC release RRCrelease message for releasing the RRC connection.

[0011] In the wireless link failure reporting method of the above first aspect, the second fast MCG link recovery information may further indicate the message type received by the UE, and the message type includes: an RRC reconfiguration RRCreconfiguration message, an RRC release RRCrelease message.

[0012] In the wireless link failure reporting method of the above first aspect, the cell identifier may be indicated by a frequencyInfoDL information element and a physCellid information element included in the reconfigurationWithSync information element.

[0013] In the wireless link failure reporting method of the above first aspect, the frequencyInfoDL information element may indicate a downlink carrier and the basic parameters of the transmission thereon, and the physCellid information element indicates a physical cell identifier.

[0014] In the wireless link failure reporting method of the first aspect described above, the UE may initiate the fast MCG link recovery process when specified conditions are met. The specified conditions include: the UE is configured with parameters for fast MCG link recovery, namely timer T316; the UE is configured with a split SRB or SRB3; neither MCG nor SCG is in a suspended state; and timer T316 is not in a running state. The timer T316 is used to monitor the fast MCG link recovery process.

[0015] According to a second aspect of the present disclosure, there is provided a user equipment, including: a processor; and a memory storing instructions; wherein, when the instructions are run by the processor, they execute the wireless link failure reporting method described above according to the context. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] To more fully understand the present disclosure and its advantages, reference will now be made to the following description taken in conjunction with the accompanying drawings, in which:

[0017] Figure 1 is a sequence diagram showing a user equipment UE in a connected state changing serving cells through a handover process.

[0018] Figure 2 is a schematic diagram showing the process of conditional handover.

[0019] Figure 3 is a flowchart showing the wireless link failure reporting method of Embodiment 1.

[0020] Figure 4 shows a block diagram of the user equipment UE involved in the present disclosure.

[0021] In the drawings, the same or similar structures are identified by the same or similar reference numerals. DETAILED DESCRIPTION

[0022] From the following detailed description of the exemplary embodiments of the present disclosure taken in conjunction with the drawings, other aspects, advantages and salient features of the present disclosure will become apparent to those skilled in the art.

[0023] In the present disclosure, the terms "include" and "comprise" and their derivatives are intended to be inclusive rather than limiting; the term "or" is inclusive and means and / or.

[0024] In this specification, the various embodiments described below for explaining the principles of the present disclosure are illustrative only and should not be construed in any way as limiting the scope of the disclosure. The following description with reference to the accompanying drawings is used to assist in a comprehensive understanding of the exemplary embodiments of the present disclosure defined by the claims and their equivalents. The following description includes various specific details to assist in the understanding, but these details should be considered merely exemplary. Accordingly, those of ordinary skill in the art should recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and structures are omitted for clarity and conciseness. Further, throughout the drawings, the same reference numerals are used for similar functions and operations.

[0025] The following takes the Long Term Evolution (LTE) / NR mobile communication system and its subsequent evolved versions as an example application environment, and specifically describes multiple embodiments according to the present disclosure. However, it should be noted that the present disclosure is not limited to the following embodiments, but is applicable to more other wireless communication systems. Without special instructions, in the present disclosure, the concepts of cell and base station can be replaced with each other; the LTE system is also used to refer to the LTE system after 5G (such as the so-called eLTE system, or the LTE system that can be connected to the 5G core network), and at the same time, LTE can be replaced with 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 change of the primary cell between cells and within a cell, that is, the primary cell of the UE changes from the source cell to the target cell, where the source cell and the target cell can be the same cell or different cells. During this process, the key or security algorithm for access layer security can also be updated accordingly. The source cell is also called the source base station, and can also be the source beam, source transmission point (TRP). The target cell can also be called the target base station, and can also be the target beam, target transmission point. The source cell refers to the cell that serves the UE before the handover process is initiated, that is, the cell from which the UE receives the RRC message containing the handover command. The target cell refers to the cell that serves the UE after the handover process is successfully completed, or the cell indicated by the target cell identifier included in the handover command, the cell to which the UE accesses when receiving the execution of the handover. The handover command described in the present disclosure is used to trigger the UE to perform a handover. In the NR system, it is the RRC reconfiguration message containing the Reconfigurationwithsync information element. Further, it is the RRC reconfiguration message containing the Reconfigurationwithsync information element for the Master Cell Group (MCG). At this time, the handover can also be called the synchronous reconfiguration of the MCG. In the LTE system, it is the RRC connection reconfiguration message containing the MobilityControlInformation information element. Among them, the synchronous reconfiguration information element or the MobilityControlInformation information element contains the configuration information of the target cell, such as the target cell identifier, the target cell frequency, the common 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 radio bearer configuration of the UE in the target cell, etc.For ease of description, in the present disclosure, the RRC reconfiguration message and the RRC connection reconfiguration message are equivalent; similarly, their response messages, the RRC reconfiguration complete message and the RRC connection reconfiguration complete message are equivalent. The RRC connection re-establishment request message and the RRC re-establishment request message are equivalent, and the RRC re-establishment message and the RRC connection re-establishment message are equivalent; similarly, their response messages, the RRC re-establishment complete message and the RRC connection re-establishment complete message are equivalent. The handover command and the RRC message containing the handover command are equivalent, referring to the RRC message or the configuration in the RRC message that triggers the UE to perform handover. The handover configuration refers to all or part of the configuration in the handover command. Cancel, release, delete, empty, and clear can be replaced with each other. Execute, use, and apply can be replaced with each other. Configure and reconfigure can be replaced with each other. Link and connection can be replaced with each other. Monitor and detect can be replaced with each other.

[0026] The following briefly describes the prior art related to the embodiments of the present disclosure.

[0027] General handover process in existing mechanisms:

[0028] The mobility of a user in the connected state is mainly achieved through the handover process, where the handover refers to the process of a UE in the RRC connected state changing its serving cell. Figure 1 It is a sequence diagram showing that a user equipment UE in the connected state changes its serving cell through the handover process. As Figure 1 shown, the handover process generally includes the following stages:

[0029] Stage 1: Measurement stage. The base station sends a measurement configuration to the user equipment (UE); the UE measures the radio link corresponding to the serving cell or neighboring cells based on this measurement configuration. When the configured measurement reporting condition is met, the UE sends a measurement report to the base station. The measurement stage is not mandatory, and the base station can also perform a blind handover of the UE when there is no valid measurement report.

[0030] Stage 2: Handover preparation stage. The base station decides whether to trigger a handover for the UE by combining the received measurement report and other factors such as base station load. If it is determined to trigger a handover 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 this handover request for the UE based on factors such as the UE's context in the handover request message and the available resources of the target base station. If it can, it sends a handover confirmation message to the source base station, where the handover confirmation message contains an inter-node RRC message, namely the handover command.

[0031] 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 procedure, and sends a confirmation message to the target base station. Among them, the random access procedure is not necessary.

[0032] Phase 4: Handover completion phase. After the target base station confirms the successful access of the UE, it sends a handover completion message to the source base station. The source base station can release the UE context saved thereon accordingly.

[0033] Conditional handover:

[0034] Secondly, conditional handover is briefly described. As mentioned before in the Release 16 technical requirements, it is required to meet the "0 ms" data interruption delay as much as possible during the mobile handover process and improve the robustness of the handover to meet the mobility requirements of seamless handover in NR. In the current handover process, one of the reasons for handover failure and long-time data transmission interruption is the failure to receive the handover command caused by untimely sending of the handover command. For this problem, a feasible method is conditional handover (abbreviated as conditional handover). Figure 2It is a schematic diagram showing the process of conditional handover. In conditional handover, a relatively conservative measurement report threshold is set so that the base station can obtain measurement results in advance and perform handover preparation in advance according to the measurement results and the selected target base station. In this way, the base station can send a handover command containing the handover candidate cell and the handover execution condition to the UE in advance before the real handover condition (relative to the conservative measurement report threshold) is met, and the condition for the UE to perform the handover is carried therein. Different from the existing handover mechanism, after receiving the conditional handover command, the UE will not immediately perform the handover, but save the received handover command configuration and start monitoring the link quality of the source cell or the target cell according to the handover execution condition carried in the handover command message to evaluate whether the handover execution condition is met. Only when it is monitored that the configured handover execution condition is met, the UE will start to execute the saved handover command and access the target cell. Generally speaking, conditional handover refers to a handover process that is only executed when one or more configured handover 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 within a certain period of time). The neighboring cell corresponds to the target cell of the handover. Generally, 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 the handover execution condition. Since the handover command is included in the RRC reconfiguration message, conditional handover CHO is also called conditional reconfiguration.

[0035] Link recovery mechanism in the existing mechanism:

[0036] Next, introduce the link recovery mechanism in the existing mechanism, i.e., versions 15 and earlier. In the existing mechanism, after the UE experiences a radio link failure (RLF) of the primary cell group or fails to execute the handover process (HandOver Failure, HOF) (i.e., T304 timeout), the UE will initiate an RRC connection re-establishment process to re-establish / recover the connection with the network side. During the initiated RRC connection re-establishment process, the UE first performs a cell selection process to select a re-establishment 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 complete message to the base station, successfully ending the RRC connection re-establishment process. The re-establishment cell refers to the cell used by the UE to send the RRC connection re-establishment request message and receive the corresponding response message for re-establishing the RRC connection in the RRC connected state. A timer T311 is defined during the RRC re-establishment process. T311 is started when the UE initiates the RRC connection re-establishment process. When a suitable cell for re-establishment is selected during the cell selection process, T311 is stopped; if T311 times out and the UE cannot select a suitable cell, at this time, the UE is generally considered to be out of coverage, and the UE will leave the RRC connected state and enter the RRC idle state or the RRC inactive state (RRC_Inactive).

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

[0038] In the current LTE system and the NR system of Release 16, when a link failure or handover failure occurs, the UE generates and saves a Radio Link Failure report (RLF report), that is, the UE variable for saving the radio link failure report is VarRLF-Report. After restoring the connection with the network side (such as through the RRC reestablishment procedure or the RRC establishment procedure), 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 there is a saved and available radio link failure report in the RRC Connection Reestablishment Complete message in the RRC connection reestablishment procedure, the RRC Connection Reconfiguration Complete message in the RRC connection reconfiguration procedure, the RRC Connection Setup Complete message in the RRC connection establishment procedure, or the RRC Connection Resume Complete message in the RRC connection resume procedure. After receiving the indication, the network side can request the UE to report the saved radio link failure report through an RRC message (indicated by the rlf-ReportReq information element in the UE Information Request message). The UE will report the saved radio link failure report (rlf-Report information element in the UE Information Response message) to the network side in response to the RRC message. The obtained radio link failure report 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 primary cell identifier where the link failure occurs, link failure type (RLF or HOF), RLF reason, the time elapsed from the connection failure to the reporting of the radio link failure, the time elapsed from the last received handover command to the connection failure (denoted as the timeConnFailure information element), etc. In addition, the RRC reestablishment cell identifier in the radio link failure report can provide additional auxiliary information for the network side.For example, if the RRC reestablishment cell information in the radio link failure report does not exist, the network side may consider that the UE has not found any suitable cells during the radio link recovery process after the link failure, that is, during the RRC connection reestablishment process. Then, when the UE experiences a radio link failure, it may be in a network coverage hole. If the RRC reestablishment cell identifier in the radio link failure report is not the source cell where the UE is located when the failure occurs, the network side may consider that the UE's failure is not due to premature handover. The above RRC reestablishment cell identifier is included in the radio link failure report by the UE during the RRC connection reestablishment process after triggering the RRC connection reestablishment request message, which is the identifier of the RRC reestablishment cell where it attempts to reestablish the RRC connection.

[0039] Fast MCG link recovery mechanism:

[0040] The Dual Link and Carrier Aggregation Enhancement Project of Release 16 (see document RP-190452) discusses a fast MCG link recovery mechanism. The so-called "fast" is relative to the existing link recovery mechanism (i.e., recovering the link connection through the RRC connection re-establishment process). In the fast MCG link recovery mechanism, when the RLF of the UE's MCG occurs, if the link quality of the UE's Secondary Cell Group (SCG) is good (i.e., no RLF occurs or timer T310 is not running, or the SCG is not in the suspended state), at this time, if neither the MCG nor the SCG is in the suspended (or interrupted) state or timer T316 is not running, the UE initiates an MCG failure information procedure, and reports the MCG link failure information to the primary base station through the SCG link (such as the split signaling radio bearer split SRB or the third signaling radio bearer SRB3), rather than directly triggering the RRC connection re-establishment process. In the MCG failure information procedure, the UE suspends the transmission on the MCG side corresponding to all SRBs and DRBs except SRB0, and resets the MAC entity corresponding to the MCG. The primary base station that receives the MCG link failure information report can send an RRC connection reconfiguration message containing a synchronization reconfiguration information element to trigger the UE to switch to a new cell or send an RRC release message to release the UE's RRC connection. This fast MCG link recovery mechanism / procedure can be applied to the case configured with MR-DC (Multi-Radio access technology Dual Connectivity), such as NE-DC (NR E-UTRA Dual Connectivity), EN-DC (E-UTRA NR Dual Connectivity), NRDC (New Radio Dual Connectivity), NGEN-DC (Next Generation-radio access network E-UTRA NR Dual Connectivity), LTE DC (intra-E-UTRAN DC), etc. In this disclosure, the MCG failure information procedure and the fast MCG link recovery procedure are equivalent.

[0041] Wireless link recovery mechanism using the saved conditional handover configuration:

[0042] After the UE is configured with conditional handover, it does not immediately perform the handover. Instead, it performs the handover according to the received and saved conditional handover configuration after the corresponding conditions are met. During the period from the moment when the UE receives the conditional handover configuration to the moment when it performs the handover according to the received conditional handover 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. The 3GPP RAN2 working group introduced a link recovery enhancement mechanism: when an RLF occurs, the UE selects a cell to perform link recovery through the cell selection process during the RRC connection reestablishment process (i.e., when the T311 timer is running). If the selected cell is a conditional handover candidate cell, the UE performs a handover to that cell according to the conditional handover configuration corresponding to that cell; if the selected cell is not a conditional handover 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 as the link failure recovery mechanism based on conditional handover configuration (for the sake of description, simply referred to as the conditional handover link recovery mechanism) in this disclosure, and it also applies to the case of HOF. The network side enables this function of the UE by setting the CHO recovery information element (denoted as the attemptCondReconf information element) in the CHO configuration to true. For a UE enabled with this function, if the cell selected during the first cell selection process after RLF / HOF is a target candidate cell, the UE can perform a CHO to that cell. In the system of Release 16, the UE is only allowed to perform one CHO recovery after a failure. 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 conditional handover, that is, the cell identified by the cell identifier in the ReconfigurationWithSync or MobilityControlInfo. The network side can configure one or more handover execution condition candidate cells for the UE at the same time.

[0043] As mentioned above, the network side can determine the RLF scenario by obtaining the reestablished cell identifier in the RLF report, so as to better optimize network parameters. In the existing mechanism, the UE includes the reestablished cell identifier in the radio link failure report only when it triggers an RRC connection reestablishment request message during the RRC connection reestablishment process attempted with the network side. In the fast MCG link recovery mechanism, this function cannot be achieved by the existing mechanism, which is an issue concerned in this disclosure. Through the method described in this disclosure, the UE can include the cell identifier of the cell where it attempts to restore the connection in the fast MCG link recovery mechanism in the radio link failure report and report it to the network side, thus providing more auxiliary information for the network side to optimize mobile performance.

[0044] In addition, when the UE is configured with a CHO recovery mechanism, if the UE experiences a link failure (RLF or HOF), the UE can perform CHO to recover the link. If the performed CHO also fails, the UE will experience two consecutive link failures. In the existing system, the radio link failure report only records the information of the most recent link failure. How to set the link failure information in the case of two consecutive link failures is also an issue of concern in the present disclosure.

[0045] In addition, as mentioned above, the timeConnFailure information element included in the radio link failure report is used to record the time elapsed from the last time the UE received an RRC reconfiguration message containing the reconfigurationwithsync synchronization reconfiguration information element until the generation of the corresponding RLF report when a radio link failure occurs. This cannot solve the situation when the UE is configured with CHO. Therefore, the present disclosure also focuses on the issue of how to set the timeConnFailure information element in the radio link failure report when the UE is configured with CHO.

[0046] The following are several embodiments executed on the UE based on the above problems in the present disclosure. In the following embodiments, the UE being configured with conditional handover includes the UE receiving an RRC message from the base station containing a conditional handover command, saving the handover configuration in the handover command, and monitoring whether the handover execution condition is satisfied according to the handover execution condition. The handover configuration refers to the RRC configuration generated by the UE according to the configuration in the handover command. Optionally, the handover configuration refers to the RRC configuration generated by the UE according to the configuration in the handover command and / or the current RRC configuration of the UE.

[0047] Embodiment 1

[0048] This embodiment provides a method for setting the fast MCG link recovery process in the radio link failure report when using the fast MCG link recovery mechanism during a radio link failure. The UE includes the information of the fast MCG link recovery process it has attempted in the radio link failure report and reports it to the network side, so that the network side can know from this information that the UE has performed the fast MCG link recovery process after the radio link failure, thereby performing more accurate network problem location to optimize network configuration parameters such as handover threshold parameters.

[0049] As an example, Figure 3 is a flowchart showing the radio link failure reporting method of Embodiment 1. As Figure 3 shown, the radio link failure reporting method of Embodiment 1 may include the following steps.

[0050] Step 1: The UE experiences an RLF of the MCG radio link.

[0051] Step 2: The UE initiates the MCG failure information procedure to restore the connection with the network side. The MCG failure information procedure is also referred to as the fast MCG link recovery procedure.

[0052] As described above, the UE generally initiates the MCG failure information procedure only when the following conditions are met: The UE is configured with the parameters for fast MCG link recovery, namely timer T316; the UE is configured with a split SRB or SRB3; neither the MCG nor the SCG is in a suspended state; and timer T316 is not running.

[0053] Timer T316 is used to monitor the MCG failure information procedure. The UE starts T316 when sending the MCG failure information message. T316 is stopped when restoring MCG transmission, when receiving the network side's response RRC release message, or when initiating the RRC re-establishment procedure. When T316 times out, the UE considers the fast MCG link recovery procedure to have failed and ended, thereby triggering the RRC re-establishment procedure to attempt to restore the connection with the network side.

[0054] Step 3: The UE sends a radio link failure report to the network side. The radio link failure report may include first fast MCG link recovery information. The first fast MCG link recovery information is used to indicate that the UE has attempted the fast MCG link recovery mechanism based on the fast MCG link recovery procedure after the radio link failure corresponding to the radio link failure report.

[0055] In one implementation, the UE may also include second fast MCG link recovery information in the RLF report. The second fast MCG link recovery information is used to indicate that after the radio link failure corresponding to the radio link failure report, in the fast MCG link recovery mechanism attempted by the UE, after sending the RRC message of MCG failure information to the network side, the UE has received the network side's response RRC message (for example, the response RRC message is an RRC reconfiguration message containing the reconfigurationWithSync information element used to instruct the UE to perform handover or an RRC release message used to release the RRC connection). Further, the second fast MCG link recovery information may also indicate the message type received by the UE, for example, whether it is an RRC reconfiguration message or an RRC release message.

[0056] In another implementation, the UE may also include third fast MCG link recovery information in the RLF report. The third fast MCG link recovery information includes a cell identifier, which is used to indicate, in the fast MCG link recovery mechanism attempted by the UE after the radio link failure corresponding to the radio link failure report, the identifier of the handover target cell in the RRC reconfiguration message containing the reconfigurationWithSync information element after the RRC message of MCG failure information is sent to the network side. Preferably, the cell identifier is indicated by the frequencyInfoDL information element and the physCellid information element included in the reconfigurationWithSync information element. The frequencyInfoDL information element indicates a downlink carrier and the basic parameters of the transmission thereon; the physCellid information element indicates a physical cell identifier.

[0057] In yet another implementation, the UE may also include fourth fast MCG link recovery information in the RLF report. The fourth fast MCG link recovery information is used to indicate that in the fast MCG link recovery mechanism attempted by the UE after the radio link failure corresponding to the radio link failure report, after the RRC message of MCG failure information is sent to the network side, no response RRC message is received from the network side, that is, T316 timeout occurs and the fast MCG link recovery process fails.

[0058] For the above first to fourth fast MCG link recovery information, the UE may include one or more of them in the RLF report.

[0059] Preferably, after the fast MCG link recovery process ends, the UE may include the above first to fourth fast MCG link recovery information in the RLF report. The end of the fast MCG link recovery process may be a successful end (when a response message from the network side is received during the operation of T316, or when it is described as the stop of T316) or a failed end (T316 times out and no response message from the network side is received). Alternatively, when the UE initiates the fast MCG link recovery process, such as when it sends an RRC message with MCG failure information or before sending this message, it includes the above first fast MCG link recovery information in the RLF report. Alternatively, when the UE initiates a handover to the target cell according to the RRC reconfiguration message received during the fast MCG link recovery process, it includes the third fast MCG link recovery information in the RLF report. The time when the handover to the target cell is initiated may also be the time when the RRC reconfiguration message is applied.

[0060] Embodiment 2

[0061] This embodiment provides a method for reporting failure information when a fast MCG link recovery mechanism is adopted during a radio link failure. The UE that has executed the fast MCG link recovery mechanism includes the corresponding link failure information in the MCG failure information message and reports it to the network side, without the need to save or report the RLF report to the network side through the UE information response message.

[0062] In this embodiment, if the UE is configured with a fast MCG link recovery mechanism or the UE initiates a fast MCG link recovery mechanism to restore the connection with the network side, the UE includes link failure related information in the MCGfailureinformation message and reports it to the network side. Preferably, when the UE experiences RLF, if the UE is configured with a fast MCG link recovery mechanism, the UE does not save the RLF report information for this RLF in the RLF reporting variable VarRLF-report. Alternatively, when the UE initiates a fast MCG link recovery mechanism, such as during the initialization phase of the fast MCG link recovery mechanism or when sending the MCGfailureinformation message, the saved RLF report corresponding to this RLF is deleted from the UE. Alternatively, during the fast MCG link recovery process of the UE, when receiving the response RRC message from the network side, the saved RLF report corresponding to this RLF is deleted from the UE. Alternatively, when the UE receives a UEinformationrequest message from the network side for requesting the UE to report an RLF report (the rlf-ReportReq information element is set to true), if the UE has performed a fast MCG link recovery mechanism after the link failure corresponding to the RLF report, the UE does not include the RLF report in the corresponding UEinformationresponse message. Alternatively, if there is a saved RLF report on the UE but it does not meet the condition that the UE is configured with a fast MCG link recovery mechanism when the RLF occurs, or in other words, it does not meet the condition that the UE has performed a fast MCG link recovery mechanism after the RLF, the UE includes the rlf-InfoAvailable information element in an uplink RRC message when sending an uplink RRC message. Preferably, the uplink RRC message is an RRC connection reestablishment complete message, an RRC connection reconfiguration complete message, an RRC connection establishment complete message, or an RRC connection recovery complete message.

[0063] Embodiment 3

[0064] This embodiment provides a method for setting an RLF report when a CHO recovery mechanism is adopted during a radio link failure executed on the UE. The UE includes the information that it has attempted the CHO recovery mechanism in the radio link failure report and reports it to the network side, so that the network side can learn from this information that the UE has performed the CHO recovery mechanism after the radio link failure, thereby performing more accurate network problem location to optimize network configuration parameters such as conditional handover threshold parameters. As an example, the RLF report setting method of Embodiment 3 may include the following steps.

[0065] Step 1: The UE initiates an RRC reestablishment process. The UE triggers the RRC reestablishment process when experiencing MCG RLF or handover failure (timer T304 expires).

[0066] Step 2: During the cell selection process in the RRC connection re - establishment procedure, i.e., when T311 is running, if a suitable cell is selected, and if the selected cell is a conditional handover candidate cell of the UE, then perform Step 3A; otherwise, if the selected cell is not a conditional handover candidate cell of the UE, then perform Step 3B.

[0067] The fact that the selected cell is a conditional handover candidate cell of the UE can be described as that the selected cell is one of the candidate cells in the conditional handover configuration saved by the UE. The master cell group configuration in the conditional handover configuration corresponding to the candidate cell contains the reconfigurationWithSync information element.

[0068] Preferably, 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.

[0069] Step 3A: The UE performs the following operations:

[0070] Operation 1: The UE performs a conditional handover to the selected cell, initiates a conditional handover procedure, applies the saved conditional handover configuration of the cell, and performs access to the selected cell.

[0071] Operation 2: The UE includes first CHO recovery information in the RLF report (VarRLF - Report) to indicate that the UE has selected a CHO candidate cell during the cell selection process after RLF / HOF (T311 is running) and has performed the CHO recovery mechanism.

[0072] In one implementation, the UE may also include second CHO recovery information in the RLF report to indicate whether the execution conditions corresponding to the CHO candidate cell selected by the UE during the cell selection process after RLF / HOF are met when performing this operation.

[0073] In another implementation, the UE may also include a third CHO recovery message in the RLF report to indicate whether the conditional handover performed by the UE for the CHO candidate cell selected during the cell selection process after RLF / HOF is successful. The successful execution of the conditional handover means that the UE successfully accesses the corresponding target cell and the corresponding random access procedure is successfully completed. The unsuccessful execution of the conditional handover means that the timer T304 corresponding to the conditional handover expires.

[0074] The execution order of Operation 1 and Operation 2 is not limited. Operation 2 may be executed before Operation 1, that is, after the UE determines that the suitable cell selected in the cell selection process in Step 2 is a conditional handover candidate cell, Operation 2 is executed. In another way, Operation 2 may be completed after Operation 1 or during the execution of Operation 1. For example, the UE executes Operation 1 in the initialization phase of initiating conditional handover in Operation 1. However, the execution of the third CHO recovery information is executed after Operation 1 is successfully or failed to be completed.

[0075] Step 3B: Continue the RRC connection re-establishment process, such as initiating the transmission of an RRC connection re-establishment request message.

[0076] Optionally, as described above, the UE determines whether the selected cell is a conditional handover candidate cell of the UE. This determination is executed when the UE is configured with conditional handover and / or the reason for initiating the RRC connection re-establishment process (or the reason for cell selection performed during the RRC connection re-establishment process) is that an RLF of the MCG or a handover failure is detected (that is, the timer for detecting the handover process (such as T304) times out, and this also includes a conditional handover failure). Optionally, the UE determines whether the selected cell is a conditional handover candidate cell of the UE when the UE enables the CHO recovery mechanism.

[0077] That the selected cell is a conditional handover candidate cell may also be described as that the selected cell is included in the saved conditional handover configuration. Preferably, it is included in the ReconfigurationWithSync information element or the mobility control information element in the saved conditional handover configuration. The UE performs a handover to the selected cell, that is, performs a handover (or synchronous reconfiguration) to this cell according to the conditional handover configuration corresponding to this cell saved. The operations for performing conditional handover include one or more of the following: starting timer T304; executing the target cell RRC configuration in the conditional handover configuration corresponding to the target cell; executing the configuration in the synchronous reconfiguration information element corresponding to the target cell; synchronizing downlink to the target cell; performing random access to the target cell; generating an RRC reconfiguration complete message and delivering it to the lower layer for transmission.

[0078] Embodiment 4

[0079] This embodiment provides a method for a UE to report an RLF report to the network, which is executed when the UE is configured with conditional handover.

[0080] In this embodiment, when the UE detects an RLF or HOF (T304 timeout), when the UE saves the RLF or HOF information in the RLF report (VarRLF-Rreport variable), for example, the timeConnFailure information element can be set in the following manner:

[0081] Method 1: Set the value of the timeConnFailure information element to the time elapsed since the start of the handover process last (most recently) performed by the UE. In the NR system, the execution of the handover refers to the execution or application of the synchronization reconfiguration (reconfigurationWithSync) process in the RRC reconfiguration message. Preferably, Method 1 is executed when the last performed handover process is a conditional handover, that is, the execution of the handover refers to when the handover execution condition is satisfied, and the saved corresponding conditional handover configuration is executed;

[0082] Method 2: If the UE is configured with CHO, that is, the UE has a saved CHO configuration, set the value of the timeConnFailure information element to the time elapsed since the RRC reconfiguration message last (most recently) received by the UE that contains the CHO configuration for the MCG. The RRC reconfiguration message containing the CHO configuration can be an RRC reconfiguration message containing the CHO execution condition configuration or the RRC reconfiguration message corresponding to the CHO candidate cell that contains the reconfigurationWithSync information element. Preferably, the CHO configuration is not used to release the CHO configuration saved on the UE.

[0083] In another implementation, the UE can include first CHO information in the RLF report, and the first CHO information is used to indicate whether the UE is configured with CHO when the RLF or HOF occurs, that is, whether the UE has a saved CHO configuration. Further, the UE includes second CHO information in the RLF report, and the second CHO information includes one or more cell identifiers, which are used to indicate those CHO candidate cells that the UE is configured with when the RLF or HOF occurs. The cell identifier can be the downlink carrier frequency and physical cell identifier corresponding to the cell, or the cell global identifier, or the CHO configuration identifier. The CHO configuration identifier is used to identify a CHO configuration, and the UE can be configured with multiple CHO configurations simultaneously.

[0084] Embodiment 5

[0085] This embodiment describes the user equipment UE of the present disclosure. Figure 4 It is a block diagram showing the user equipment UE involved in the present invention. As Figure 4As 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. Program instructions are stored on the memory 402. When executed by the processor 401, these instructions can perform various methods such as the above-mentioned wireless link failure reporting method and wireless link failure setting method described in detail in the present invention.

[0086] In the present disclosure, some different embodiments can work together.

[0087] In the present disclosure, a "base station" refers to a mobile communication data and control switching center with a relatively large transmission power and a relatively wide coverage area, including functions such as resource allocation and scheduling, data reception and transmission, etc. A "user equipment" refers to a user mobile terminal, for example, including a mobile phone, a notebook, and other terminal devices that can perform wireless communication with a base station or a micro base station.

[0088] The methods and the related devices of the present disclosure have been described above in combination with the preferred embodiments. Those skilled in the art can understand that the methods shown above are only exemplary. The methods of the present disclosure are not limited to the steps and sequences shown above. The base stations and user equipments shown above may include more modules. For example, they may also include modules that can be developed or will be developed and can be used for base stations, MMEs, or UEs, etc. The various identifiers shown above are only exemplary rather than restrictive, and the present disclosure is not limited to the specific cells that are examples of these identifiers. Those skilled in the art can make many changes and modifications according to the teachings of the shown embodiments.

[0089] The program running on the device according to the present disclosure can 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 the information processed by the program can 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.

[0090] The programs for implementing the functions of the various embodiments of the present disclosure can be recorded on a computer-readable recording medium. The corresponding functions can be implemented by causing a computer system to read the programs recorded on the recording medium and execute these programs. Here, the so-called "computer system" can be a computer system embedded in the device, and may include an operating system or hardware (such as peripheral devices). A "computer-readable recording medium" can be a semiconductor recording medium, an optical recording medium, a magnetic recording medium, a recording medium for temporarily storing a dynamic program, or any other recording medium readable by a computer.

[0091] The various features or functional modules of the devices used in the above embodiments may be implemented or executed by circuits (e.g., single or multi-chip integrated circuits). The circuits designed to perform the functions described in this specification may include 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 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 that replace existing integrated circuits emerge due to the progress of semiconductor technology, one or more embodiments of the present disclosure may also be implemented using these new integrated circuit technologies.

[0092] In addition, the present disclosure is not limited to the above embodiments. Although various examples of the described 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 devices, kitchen devices, cleaning devices, air conditioners, office equipment, vending machines, and other household appliances.

[0093] As described above, the embodiments of the present disclosure have been described in detail with reference to the 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 gist 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. Furthermore, the components having the same effects described in the above embodiments may be substituted for each other.

Claims

1. A user equipment UE, comprising: a processor; and a memory storing instructions, wherein, based on the instructions, the processor is configured to: store a radio link failure report in a variable VarRLF-Report when a radio link failure RLF occurs; send a MCG failure information message to the network and start a timer T316 when initiating a master cell group MCG failure information procedure; and when the processor receives an RRC release message or an RRC reconfiguration message including a synchronization reconfiguration information element from the network while the timer T316 is running, clear the radio link failure report stored in the variable VarRLF-Report when receiving the RRC release message or the RRC reconfiguration message, wherein the processor is further configured to: in the case where the timer T316 expires: trigger an RRC connection re-establishment procedure; and send the radio link failure report to the network, wherein the sent radio link failure report includes information for indicating that the timer T316 has expired and the MCG failure information procedure has failed.

2. A method performed by a user equipment UE, comprising: storing a radio link failure report in a variable VarRLF-Report when a radio link failure RLF occurs; sending a MCG failure information message to the network and starting a timer T316 when initiating a master cell group MCG failure information procedure; and when the UE receives an RRC release message or an RRC reconfiguration message including a synchronization reconfiguration information element from the network while the timer T316 is running, clear the radio link failure report stored in the variable VarRLF-Report when receiving the RRC release message or the RRC reconfiguration message, wherein in the case where the timer T316 expires, the method further comprises: triggering an RRC connection re-establishment procedure; and sending the radio link failure report to the network, wherein the sent radio link failure report includes information for indicating that the timer T316 has expired and the MCG failure information procedure has failed.

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