Wireless link failure recovery method and user equipment

Abstract

The present disclosure provides a radio link failure recovery method and user equipment. The radio link failure recovery method includes: when the user equipment (UE) detects a handover failure, the UE falls back to the configuration used by the source cell when the UE has a saved conditional handover (CHO) configuration or when the UE has a saved conditional handover (CHO) configuration and CHO recovery is enabled, the UE falls back to the configuration used by the source cell, where the configuration used by the source cell includes one or more of a physical layer dedicated configuration, a media access control (MAC) layer configuration, and a semi-static SPS configuration.

Description

Technical Field

[0001] The present disclosure relates to the field of wireless communication technology, and more particularly to a recovery method after a wireless link failure and a corresponding user equipment. Background Art

[0002] In June 2018, the 3rd Generation Partnership Project (3GPP) RAN#80 plenary meeting approved a new research project for 5G technical standards (see non-patent literature: RP-181433: New WID on NR (New Radio) mobility enhancements). In addition, a new research project based on Release 16 of the Long Term Evolution (LTE) system was also approved (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, achieving zero or near zero millisecond handover interruption time during cell handovers, enhancing handover robustness, and reducing handover failure rates. Among the solutions being studied to reduce handover interruption time and / or enhance handover robustness is conditional handover (CHO). In the CHO mechanism, the base station sends a handover command to the UE in advance, which contains conditional configuration information. When the configured conditions are met, the UE performs handover according to the previously received handover command. This early handover command delivery improves the success rate of handover command reception, thereby improving the handover success rate and avoiding service interruption and delay caused by handover failures due to failure to receive handover commands.

[0003] This disclosure proposes solutions to some problems in implementing CHO in NR systems and LTE systems. Summary of the Invention

[0004] The present disclosure aims to address the issue of implementing CHO technology in NR and LTE systems. More specifically, the present disclosure addresses the issue of how to utilize a saved CHO configuration to restore a link connection when a radio link fails. The present disclosure also provides a radio link failure recovery method for user equipment (UE) when a handover fails, and a corresponding UE.

[0005] According to the first aspect of the present disclosure, a wireless link failure recovery method is proposed, including: a user equipment UE detects that a handover failure occurs; when the UE has a saved conditional handover CHO configuration, or when the UE has a saved conditional handover CHO configuration and is enabled for CHO recovery, the UE falls back to the configuration used by the source cell, and the configuration used by the source cell includes one or more of a physical layer dedicated configuration, a media access control MAC layer configuration, and a semi-static SPS configuration.

[0006] In the wireless link failure recovery method of the first aspect above, when the UE does not have a saved CHO configuration or is not enabled for CHO recovery, the UE may fall back to the configuration used in the source cell except for the physical layer dedicated configuration, MAC layer configuration and / or SPS configuration.

[0007] In the radio link failure recovery method of the first aspect, the handover failure may include: the UE failing to perform CHO, and the UE failing to perform non-CHO.

[0008] In the wireless link failure recovery method of the first aspect above, it may also include: the UE performs a CHO recovery process, and in the cell selection process of the CHO recovery process, when the selected cell is a CHO candidate cell, the UE applies the saved CHO configuration and performs CHO to the CHO candidate cell; when the selected cell is not a CHO candidate cell, the UE initiates a radio resource control RRC connection re-establishment process.

[0009] In the wireless link failure recovery method of the first aspect above, during the initialization phase of initiating the CHO recovery process, the UE may perform the following operations: if timer T310 is running, stop timer T310; if timer T312 associated with the main cell group MCG is running, stop timer T312.

[0010] According to a second aspect of the present disclosure, a wireless link failure recovery method is provided, including: a user equipment UE detects that a handover failure occurs; the UE falls back to a configuration used in a source cell except for a physical layer dedicated configuration, a media access control MAC layer configuration and / or a semi-static SPS configuration; and the UE performs a conditional handover CHO recovery process, and in a cell selection process of the CHO recovery process, if the selected cell is a CHO candidate cell, the UE falls back to the physical layer dedicated configuration, MAC layer configuration and / or SPS configuration used in the source cell.

[0011] In the radio link failure recovery method of the second aspect, the UE may initiate a radio resource control (RRC) connection re-establishment process when the selected cell is not the CHO candidate cell during the cell selection process.

[0012] In the radio link failure recovery method of the second aspect, when the selected cell is the CHO candidate cell, the UE may perform CHO to the CHO candidate cell based on the fallback configuration and applying the saved CHO configuration.

[0013] In the wireless link failure recovery method of the second aspect above, during the initialization phase of initiating the CHO recovery process, the UE may perform the following operations: if timer T310 is running, stop timer T310; if timer T312 associated with the main cell group MCG is running, stop timer T312.

[0014] 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

[0015] 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:

[0016] Figure 1 This is a sequence diagram showing how a connected user equipment UE changes its serving cell through a handover procedure.

[0017] Figure 2 This is a schematic diagram showing the flow of conditional switching.

[0018] Figure 3 This is a flowchart showing wireless link recovery based on conditional handover according to the first embodiment.

[0019] Figure 4 This is a flowchart showing radio link recovery based on conditional switching according to the second embodiment.

[0020] Figure 5 A block diagram showing a user equipment UE involved in the present disclosure.

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

[0022] 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.

[0023] In this disclosure, the terms "include" and "including" and their derivatives mean inclusion without limitation; the term "or" is inclusive, meaning and / or.

[0024] In this specification, the various embodiments described below for describing the principles of the present disclosure are merely illustrative 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 intended to assist in a comprehensive understanding of 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 have been omitted. In addition, throughout the drawings, the same reference numerals are used for similar functions and operations.

[0025] The following describes multiple implementations of the present disclosure using the Long Term Evolution (LTE) / NR mobile communication system and its subsequent evolutionary versions as example application environments. It should be noted that the present disclosure is not limited to the following implementations, but is applicable to many other wireless communication systems. Unless otherwise specified, in the present disclosure, the concepts of cell and base station can be interchangeable; the LTE system can also be a 5G or later LTE system (such as an eLTE system, or an LTE system that can be connected to a 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 (PCell) 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, where the source cell and the target cell can be the same cell or different cells. During 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 (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 called synchronous reconfiguration. In the LTE system, it is an RRC connection reconfiguration message containing a mobility control information (MobilityControlInformation) 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.However, the embodiments described in the present disclosure may also be applicable to the switching or change of the primary secondary cell (PSCell). The PSCell refers to the service cell in which the UE performs a random access process or an initial physical uplink shared channel (PUSCH) transmission during the change or addition of the secondary cell group in the secondary cell group (SCG). Generally, PCell and PSCell are collectively referred to as special cells (SpCell). For ease of description, in the present disclosure, the RRC reconfiguration message and the RRC connection reconfiguration message are equivalent; similarly, its response message RRC reconfiguration completion message and the RRC connection reconfiguration completion message are equivalent. The RRC connection reestablishment request message and the RRC reestablishment request message are equivalent, and the RRC reestablishment message and the RRC connection reestablishment message are equivalent; similarly, its response message RRC reestablishment completion message and the RRC connection reestablishment completion message are equivalent. The switching command and the RRC message containing the switching command are equivalent, and refer to the RRC message that triggers the UE to perform the switching or the configuration in the RRC message. A handover configuration refers to all or part of the configuration in a handover command. Cancel, release, delete, clear, and purge are interchangeable. Execute, use, and apply are interchangeable. Configure and reconfigure are interchangeable. Link and connection are interchangeable. Monitor and detect are interchangeable. Conditional handover commands and conditional handover configurations are interchangeable.

[0026] In the present application, after receiving a Radio Resource Control (RRC) message containing 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.

[0027] The following briefly describes the prior art involved in the embodiments of the present disclosure.

[0028] The general switching process in the existing mechanism:

[0029] User mobility in a connected state is mainly achieved through a handover process, where the handover refers to a process in which a UE in an RRC connected state changes a serving cell (primary cell). Figure 1 This is a sequence diagram showing how a connected user equipment UE changes its serving cell through a handover process. Figure 1 As shown in Figure 1, the switching process generally includes the following stages:

[0030] Phase 1: Measurement Phase. The base station sends a measurement configuration to the user equipment (UE). Based on this measurement configuration, the UE measures the radio link corresponding to the serving cell or neighboring cell. When the configured measurement reporting conditions are met, the UE sends a measurement report to the base station. The measurement phase is optional; the base station can also perform a blind handover of the UE when it does not have a valid measurement report.

[0031] Phase 2: Handover preparation phase. The base station determines whether to trigger a handover for the UE based on the received measurement report and other factors such as base station load. If a handover is determined to be 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 accepted, it replies to the source base station with a handover confirmation message, which contains an inter-node RRC message, namely the handover command.

[0032] Phase 3: Handover Execution. The source eNB issues a handover command to the UE and begins forwarding the UE's data to the target eNB. Upon receiving the handover command, the UE immediately applies the configuration specified in the handover command and executes the handover. It then accesses the target eNB through a random access procedure and sends a confirmation message to the target eNB. The random access procedure is optional.

[0033] 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 then release the UE context stored on it.

[0034] Condition-based switching:

[0035] In the above-mentioned general handover process, one reason for handover failure and long data transmission interruption is that the handover command is not sent in time, resulting in failure to receive the handover command. To solve this problem, Release 16 introduced conditional handover (CHO). Figure 2This 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 obtains measurement results in advance and performs handover preparation in advance based on the measurement results and the selected target base station. In this way, the base station can send a handover command RRC message containing CHO candidate cells and corresponding CHO execution conditions to the UE in advance before the actual handover conditions (relative to the conservative measurement report threshold) are met. The RRC message (RRC connection reconfiguration message in the LTE system) supports containing more than one CHO candidate cell and the CHO configuration corresponding to each CHO candidate cell (i.e., the configuration contained in the RRC connection reconfiguration message configured by the candidate target cell) and CHO execution conditions. After receiving the conditional handover command, the UE does not immediately perform the handover, but saves the received CHO configuration (i.e., the configuration contained in the RRC reconfiguration message configured by the target cell) and starts monitoring the link quality of the source cell or the link quality of the target cell based on the CHO execution conditions corresponding to the CHO candidate cell carried in the handover command message to evaluate whether the CHO execution conditions are met. Only when it is detected that one or more configured CHO execution conditions are met, the UE starts to perform switching according to the saved CHO configuration and access the target cell. Generally speaking, if the CHO configuration contains a full configuration information element (fullconfig) (or the fullconfig information element is set to TRUE), the UE directly applies the CHO configuration to switch to the target cell, that is, the CHO configuration is independent of the source cell configuration. Otherwise, the UE applies the CHO configuration of the target cell based on the source cell configuration, that is, the CHO configuration (saved by the UE) is an incremental configuration based on the source cell configuration. During the switching process, the UE will stop evaluating the configured CHO execution conditions. In short, conditional switching refers to a switching process that is only performed when one or more configured CHO execution conditions are met. The CHO execution condition can be a measurement event, such as the measurement event A3 (the signal quality of the neighboring cell is better than that of the serving cell by more than an offset for a period of time). The neighboring cell corresponds to a CHO candidate target cell. A CHO candidate cell can correspond to one or more CHO execution conditions. When multiple CHO execution conditions are configured for a candidate cell, the UE will only initiate the corresponding handover when all CHO execution conditions are met. Generally speaking, all measurement events defined in 3GPP standards 36.331 and 38.331 (see section 5.5.4), such as A1 to A5, can be included as CHO execution conditions in the CHO handover command.

[0036] Link recovery mechanism in existing mechanisms:

[0037] First, let's briefly introduce Radio Link Failure (RLF) and Handover Failure (HOF). When one or more of the following situations occurs, the UE will consider that an MCG RLF has occurred:

[0038] Case 1: Timer T310, used for radio link failure detection, times out. When the UE's RRC layer detects a physical layer problem in the primary cell (Pcell), i.e., receives N310 consecutive out-of-sync indications from the lower layer, and if timers T300 (for detecting the RRC connection establishment process), T301 (for detecting the RRC connection re-establishment process), T304 (for detecting the handover process), or T311 (for detecting the cell selection phase during the RRC connection re-establishment process) used for RRC process control are not running, T310 is started. N310 is a constant configured by the network. If the network does not configure this constant, the UE uses a predefined default value.

[0039] Case 2: Timer T312 associated with the MCG expires. T312 is used to detect radio link failure when a measurement report is triggered. If T310 is running when the UE's RRC layer triggers a measurement report with the trigger type set to event triggered and a measurement ID configured to use T312, it starts the corresponding T312. More specifically, in the LTE system, T312 is initiated when one of the following conditions is met: Condition 1: For a measurement ID, if the trigger type is set to event trigger, and all layer 3 filtered measurements of one or more applicable cells have satisfied the entry condition applicable to the event within timetoTrigger, and the measurement report list (VarMeasReportList) stored in the UE does not contain any measurement reporting item for the measurement ID, if the UE supports T312 and the configuration for the event includes a T312 available configuration (useT312 information element), if T310 is running, and if T312 is not running, T312 is initiated. Condition 2: For a measurement ID, if the trigger type is set to event, and all Layer 3 filtered measurements for one or more applicable cells not included in the triggered cell list (cellsTriggeredList) satisfy the entry condition for the event within timetoTrigger, and if the UE supports T312 and the configuration for the event includes a T312 enabled configuration (useT312 information element), then if T310 is running, or if T312 is not running, then T312 is started. The value of T312 is the T312 value configured by the network for the measurement object associated with the measurement ID.

[0040] Case 3: A random access failure indication is received from the Medium Access Control (MAC) layer and the timer T300, T301, T304 or T311 used for RRC process control is not running. The MAC refers to the MAC corresponding to the MCG.

[0041] Case 4: An indication is received from the Radio Link Control (RLC) layer corresponding to the MCG, where the indication is used to indicate that the maximum number of RLC retransmissions for a signaling radio bearer (SRB) or a data radio bearer (DRB) has been reached.

[0042] For HOF, the UE determines the occurrence of HOF based on the timer T304 that detects the switching process. The UE starts T304 when it starts to perform a switch, and applies the corresponding RRC configuration in the switch command, and stops T304 when the switch is successfully completed. If T304 times out, the UE considers that a HOF has occurred. After the HOF, the UE falls back to the configuration used in the source cell before the switch was executed. The configuration includes the state variables and parameters corresponding to each radio bearer, but does not include physical layer dedicated configuration (referring to the configuration in the PhysicalConfigDedicated information element), MAC dedicated configuration (referring to the configuration in the mac-Mainconfig information element) and semi-static configuration (referring to the configuration in the sps-config information element).

[0043] Secondly, the link recovery mechanism in the existing mechanism is introduced. After a radio link failure (RLF) or a handover failure (HOF) occurs in the main cell group, the UE will initiate an RRC connection re-establishment process to re-establish / 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 response message received by the UE is 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 reestablishment 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).

[0044] Radio link recovery using saved conditional handover configuration:

[0045] In the conditional handover scenario, from the moment the UE receives and saves a CHO configuration to the moment the corresponding CHO condition is met and the handover is performed according to the received CHO configuration, the UE still maintains communication with the source base station. The 106th and 107th meetings of the 3GPP RAN2 Working Group reached a conclusion on the execution of the CHO process during RLF / HOF: When RLF or HOF occurs, the UE first selects a cell through the cell selection process to perform link recovery. If the selected cell is a CHO candidate cell (that is, the cell corresponds to a saved CHO configuration), the UE performs handover to the cell according to the CHO configuration corresponding to the cell; if the selected cell is not a CHO candidate cell, the UE attempts to restore the connection with the network side by sending an RRC connection establishment request to the selected cell, that is, adopting the traditional RRC connection re-establishment process. This enhancement of the link recovery mechanism is referred to as a link failure recovery mechanism based on CHO configuration (referred to as CHO link recovery mechanism) in this disclosure. Generally, the serving cell enables the CHO link recovery function of the UE through the enable indication in the RRC signaling. Currently, the UE can only perform CHO recovery once after RLF / HOF occurs. That is, if the CHO recovery fails, the UE will directly enter the idle state. In another implementation, the UE directly triggers the RRC re-establishment process.

[0046] Radio Link Recovery via MCG Failure Information Procedure

[0047] The 3GPP RAN2 working group also introduced a fast MCG link recovery mechanism. The fast MCG link recovery mechanism is relative to the existing link recovery mechanism (i.e., restoring the link connection through the RRC connection re-establishment process), and is also called the MCG failure information process. The purpose of this process is to notify the main base station that the UE has an MCG radio link failure. For a UE configured with a split SRB1 or SRB3, when the UE's MCG detects an RLF, if the UE's MCG and SCG are not suspended and are configured with a fast MCG link recovery function, the UE initiates the MCG failure information process and reports the MCG link failure information to the main base station through the SCG link in the MCG failure information RRC message. The main 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 UE's connection. Timer T316 is used to detect the MCG failure information process. The UE starts T316 when sending the MCG failure information RRC message; stops T316 when the MCG transmission is restored or a response is received from the network side (such as an RRC release message or an RRC reconfiguration message for instructing UE switching) or the RRC re-establishment process is initiated; if T316 times out, the UE considers that the MCG failure information process is over and initiates the RRC re-establishment process to recover the MCG link. The fast MCG link recovery mechanism can be applied to situations where MR-DC (Multi-Radio access technology Dual Connectivity) is configured, such as NE-DC (NR E-UTRA Dual Connectivity), EN-DC (E-UTRA NR Dual Connectivity), NR DC (New Radio Dual Connectivity), NGEN-DC (Next Generation-radio access network E-UTRA NR Dual Connectivity), LTE DC (intra-E-UTRAN DC), etc.

[0048] This disclosure primarily addresses the problem of how a CHO-configured UE can restore its connection with the network during RLF / HOF. More specifically, this disclosure addresses the following issues: how to apply the saved CHO configuration to switch to the target cell during HOF; how to prevent a recurrence of radio link failure during an ongoing CHO link recovery process; or how to coordinate the two link recovery mechanisms to restore the link when both the CHO recovery mechanism and the MCG failure information mechanism are configured on the UE.

[0049] The following are several embodiments of the present disclosure executed on a UE based on the above-mentioned problems.

[0050] Example 1

[0051] This embodiment is executed on the UE, and further executed at the RRC layer of the UE. When a handover failure (HOF) occurs to cell A, the UE's RRC configuration is rolled back to the configuration of the source cell before the handover was performed. However, the configuration does not include the physical layer-specific configuration and MAC configuration. In other words, the physical layer-specific configuration and MAC configuration currently used by the UE are all from the configuration of the handover target cell A corresponding to this HOF. If the UE has a saved CHO configuration and the CHO recovery function is enabled by the network side, the UE may initiate a CHO recovery process to the CHO candidate cell B to restore the link. When the UE applies the CHO configuration corresponding to the CHO candidate cell B during the CHO recovery process, if the CHO configuration is an incremental (delta) configuration, the physical layer-specific configuration and MAC layer configuration of cell B applied by the UE are based on the current relevant configuration (i.e., cell A), and the saved CHO configuration of cell B is not an incremental configuration of the relevant configuration of cell A. This will result in inconsistent configurations applied by the network side and the UE after the CHO handover. This mismatched configuration can lead to further configuration / link failures. This embodiment provides a solution to this problem. In this embodiment, when a HOF occurs, a UE that can perform CHO recovery to restore a link can roll back the physical layer-specific configuration or the MAC layer-specific configuration to the configuration of the source cell before the handover. This allows the UE to apply the saved incremental configuration of the CHO candidate cell based on the configuration of the source cell before the handover when performing a subsequent CHO handover with CHO recovery, thereby maintaining RRC configuration consistency with the network side after the handover.

[0052] As an example, Figure 3 1 is a flow chart showing the wireless link recovery based on conditional switching in Example 1. Figure 3 As shown, an example of a radio link failure recovery method based on conditional switching includes the following steps.

[0053] Step 1: The UE detects that a handover failure occurs (T304 times out). The handover failure refers to the failure of the UE to perform a traditional non-CHO handover, or it may be the failure of the UE to perform a CHO handover. The traditional non-CHO handover failure refers to the UE immediately applying the received configuration to perform a handover to the target cell after receiving the RRC reconfiguration message containing the handover command, including handover without random access (rach-skip is configured in the handover command), Make-Before-Break (MBB) handover (makebeforebreak is configured in the handover command), and Dual Active Protocol Stack (DAPS) handover (referring to maintaining the connection with the source cell during the handover process after receiving the RRC message for handover until the source cell is released after successfully accessing the target cell, and the RRC message contains an indication / enablement of the DAPS handover configuration).

[0054] Step 2: If the UE has a saved CHO configuration, or if the UE has a saved CHO configuration and is enabled for CHO recovery, when HOF occurs in step 1, the UE falls back to the configuration used by the source cell. Specifically, when CHO recovery is enabled for the UE by default, if the UE has a saved CHO configuration, the UE falls back to the configuration used by the source cell when HOF occurs. In addition, when CHO recovery is not enabled for the UE by default, if the UE has a saved CHO configuration and is enabled for CHO recovery, the UE falls back to the configuration used by the source cell when HOF occurs. Furthermore, the configuration used by the source cell includes one or more of a physical layer dedicated configuration, a MAC layer configuration, and an SPS configuration. Being enabled for CHO recovery means that the UE is configured with a CHO recovery enable indication (such as identified by an attemptCHO information element) in the received RRC message containing the CHO configuration, or the CHO recovery enable indication is set to "TURE" or "1". The CHO recovery enable indication is used to allow the UE to recover the link by performing CHO after a link failure if the selected cell is a CHO candidate cell. Specifically, if this indication is present in the RRC message, then during the first cell selection process after a link failure, if the selected cell is a CHO candidate cell, the UE performs CHO to that cell.

[0055] Another way to describe the operation described in this step is: when a handover failure occurs, if the UE has a saved CHO configuration, or the UE has a saved CHO configuration and is enabled for CHO recovery, the UE falls back to the configuration used by the source cell; otherwise, if the UE does not have a saved CHO configuration or is not enabled for CHO recovery, it falls back to the configuration used in the source cell except for the physical layer dedicated configuration, MAC layer configuration and / or SPS configuration.

[0056] Step 3: The UE performs a CHO recovery procedure, including: the UE performs a cell selection procedure. If the selected (suitable) cell is a CHO candidate cell, the UE applies the saved CHO configuration for that cell and performs CHO to that cell; otherwise, the UE initiates an RRC connection re-establishment procedure. The UE applies the saved CHO configuration based on the UE fallback configuration described in step 2. Step 3 is optional.

[0057] Apparently, this embodiment further includes, before step 1, the following steps: the UE receives an RRC reconfiguration message from the source cell containing a CHO configuration and CHO execution conditions, saves the CHO configuration, and begins monitoring whether the CHO execution conditions are satisfied based on the CHO execution conditions contained in the RRC message. Before the HOF in step 1, the UE may also perform a handover to the target base station. The fact that the UE has a saved CHO configuration can also be described as the UE being configured for CHO. The source cell is the source PCell.

[0058] Example 2

[0059] This embodiment is executed on the UE and further executed at the RRC layer of the UE. This embodiment is consistent with the scenario described in Example 1 and is used to maintain consistency of the RRC configuration with the network side after the CHO recovery process is performed after a handover failure. This embodiment differs from Example 1 in that, during the CHO recovery process, the UE rolls back its physical layer configuration, etc., to the corresponding configuration used by the source cell before the handover failure occurred, thereby ensuring that the UE can correctly apply the saved CHO configuration corresponding to the selected cell to perform the handover.

[0060] As another example, Figure 4 is a flow chart showing wireless link recovery based on conditional switching in Example 2. Figure 4 As shown, another example of the radio link failure recovery method based on conditional switching includes the following steps.

[0061] Step 1: The UE experiences a handover failure (T304 timeout). This handover failure refers to either a failure of the UE to perform a traditional non-CHO handover or a failure of the UE to perform a CHO handover. This traditional non-CHO handover failure occurs when the UE, upon receiving an RRC reconfiguration message containing a handover command, immediately applies the received configuration to perform a handover to the target cell. This includes handovers without random access, MBB handovers, and DAPS handovers.

[0062] Step 2: When HOF occurs in step 1, the UE falls back to the configuration used in the source cell except for the physical layer dedicated configuration, MAC layer configuration and / or SPS configuration.

[0063] Step 3: The UE performs a CHO recovery process, including: the UE performs a cell selection process. If the selected (suitable) cell is a CHO candidate cell, the UE performs the following operations: falls back to the physical layer dedicated configuration, MAC layer configuration, and / or SPS configuration used in the source cell, and applies the CHO configuration saved for the cell based on the current configuration to perform CHO to the cell; otherwise, if the selected cell is not a CHO candidate cell, the UE initiates an RRC connection re-establishment process. The application of the CHO configuration saved for the cell based on the current configuration refers to applying the saved CHO configuration based on the RRC configuration after the UE falls back in steps 2 and 3.

[0064] Preferably, the UE performs step 3 only when it has a saved CHO configuration and is enabled for CHO recovery. The enabling of CHO recovery is described in Example 1 and will not be repeated here.

[0065] Apparently, this embodiment further includes, before step 1, the following steps: the UE receives an RRC reconfiguration message from the source cell containing a CHO configuration and CHO execution conditions, saves the CHO configuration, and begins monitoring whether the CHO execution conditions are satisfied based on the CHO execution conditions contained in the RRC message. Before the HOF in step 1, the UE may also perform a handover to the target base station. The fact that the UE has a saved CHO configuration can also be described as the UE being configured for CHO. The source cell is the source PCell.

[0066] Example 3

[0067] This embodiment is executed on the UE and further executed at the RRC layer of the UE. This embodiment is consistent with the scenario described in Example 1 and is used to maintain consistency of the RRC configuration with the network side after the CHO recovery process is performed after a handover failure. This embodiment differs from Example 1 in that, during the CHO recovery process, the UE does not roll back its physical layer configuration, etc. to the corresponding configuration used by the source cell before the handover failure occurs, but instead uses the corresponding system default configuration, thereby ensuring that the UE can correctly apply the saved CHO configuration corresponding to the selected cell to perform the handover.

[0068] Step 1: The UE experiences a handover failure (T304 timeout). This handover failure refers to either a failure of the UE to perform a traditional non-CHO handover or a failure of the UE to perform a CHO handover. This traditional non-CHO handover failure occurs when the UE, upon receiving an RRC reconfiguration message containing a handover command, immediately applies the received configuration to perform a handover to the target cell. This includes handovers without random access, MBB handovers, and DAPS handovers.

[0069] Step 2: When HOF occurs in step 1, the UE falls back to the configuration used in the source cell except for the physical layer dedicated configuration, MAC layer configuration and / or SPS configuration.

[0070] Step 3: The UE performs a CHO recovery process, including: the UE performs a cell selection process. If the selected (suitable) cell is a CHO candidate cell, the UE performs the following operations: applying the system default physical layer dedicated configuration, default MAC layer configuration, and / or default SPS configuration, and applying the CHO configuration saved for the cell based on the current configuration, and performing CHO to the cell; otherwise, if the selected cell is not a CHO candidate cell, the UE initiates an RRC connection re-establishment process. The application of the CHO configuration saved for the cell based on the current configuration refers to applying the saved CHO configuration based on the RRC configuration after the UE falls back in step 2 and the system default configuration applied in step 3.

[0071] Preferably, the UE performs step 3 only when it has a saved CHO configuration and is enabled for CHO recovery. The enabling of CHO recovery is described in Example 1 and will not be repeated here.

[0072] Step 4: When the UE performs CHO to the selected cell during the CHO recovery process, it sends an indication message to the target cell. The indication message is used to indicate that this CHO is initiated due to a link failure (HOF). Furthermore, the indication message is used to indicate that the UE applies the system default physical layer dedicated configuration, MAC layer configuration or SPS configuration in this CHO. The indication message can be included in the first PUSCH (message 3 transmitted using the resources allocated in the random access response) in the random access process of accessing the target base station in the form of a MAC control element (MAC Control Element, MAC CE) or an RRC message (handover response message (RRC connection reconfiguration completion generated during T304 operation and sent to the target cell)), or sent in the first PUSCH after the handover is successful in the form of a MAC CE or an RRC message. The handover success can be the successful completion of the random access process, such as the RRC layer receiving an indication of the successful completion of the random access process from the MAC layer.

[0073] Apparently, this embodiment further includes, before step 1, the following steps: the UE receives an RRC reconfiguration message from the source cell containing a CHO configuration and CHO execution conditions, saves the CHO configuration, and begins monitoring whether the CHO execution conditions are satisfied based on the CHO execution conditions contained in the RRC message. Before the HOF in step 1, the UE may also perform a handover to the target base station. The fact that the UE has a saved CHO configuration can also be described as the UE being configured for CHO. The source cell is the source PCell.

[0074] Example 4

[0075] This embodiment is executed on the UE, and further executed on the RRC layer of the UE. This embodiment is consistent with the scenario described in Example 3, and is used to solve the problem of maintaining consistency of the RRC configuration with the network side after the CHO recovery process is performed after the handover fails. This embodiment is different from Example 3 in that, in order to ensure the configuration consistency between the UE and the network side, the UE always applies the system default physical layer dedicated configuration, MAC configuration or SPS configuration when executing CHO, regardless of whether the CHO is triggered by a link failure. In this way, the network side maintains consistency with the UE in the physical layer dedicated configuration, MAC layer configuration or SPS configuration, thereby ensuring that the UE can correctly apply the saved CHO configuration corresponding to the selected cell to perform the handover.

[0076] Step 1: The UE receives an RRC reconfiguration message including a CHO configuration and a CHO execution condition from a source cell, saves the CHO configuration, and starts monitoring whether the CHO execution condition is satisfied according to the CHO execution condition included in the RRC message.

[0077] Step 2: The UE performs CHO. During the CHO process, the UE performs the following operations: applying the system's default physical layer dedicated configuration, MAC configuration, or SPS configuration; and applying the saved CHO configuration corresponding to the target cell. The CHO configuration is an enhanced configuration based on the current UE configuration. Preferably, the CHO configuration does not include a full configuration indication.

[0078] Preferably, the UE performs the operation in step 2 only when CHO recovery is enabled. The enabling of CHO recovery is described in Embodiment 1 and will not be repeated here.

[0079] The UE having a saved CHO configuration may also be described as the UE being configured with CHO. The source cell is a source PCell.

[0080] In this embodiment, the physical layer dedicated configuration, MAC layer configuration, or SPS configuration in the CHO configuration (configuration included in the RRC reconfiguration message) configured by the target candidate cell and saved by the UE is always based on the corresponding configuration by default in the system. In other words, the above configurations in the CHO configuration configured by the target candidate cell are always incremental configurations based on the corresponding configuration by default in the system.

[0081] Example 5

[0082] This embodiment is executed at the RRC layer of the UE. As described in the background technology section, the monitoring timers currently used to trigger RLF are T310 and T312. The triggering conditions of these two timers are different and can be in running state at the same time. When one of the timers times out, RLF will be triggered. At this time, the other timer is still running. During the CHO recovery process, if the other running timer times out at this time, it will cause the UE to enter the RLF state again, thereby re-executing a CHO recovery process, which will prolong the link interruption time and affect the continuity of service. In this embodiment, if the UE enters a CHO recovery process, the UE will stop the running RLF-related timer to avoid the above situation and shorten the link interruption time.

[0083] Step 1: The UE experiences RLF. For example, when T310 or T312 times out, the UE declares RLF.

[0084] Step 2: UE initiates CHO recovery process. In the initialization phase of initiating CHO recovery process, UE performs the following operations: if there is T310 running, then stop T310; if there is T312 associated with the running MCG, then stop T312.

[0085] Preferably, the initialization phase of initiating the CHO recovery process is before initiating the cell selection process. Alternatively, after an RLF / HOF occurs, the UE performs the timer stop operation. Preferably, the UE performs step 2 only when a saved CHO configuration is available and CHO recovery is enabled. Enabling CHO recovery is described in Example 1 and is not further described here.

[0086] Step 3: The UE performs a CHO recovery process. The CHO recovery process is as described above and will not be repeated here.

[0087] Example 6

[0088] This embodiment provides a method for restoring a link when an RLF of MCG occurs in a UE with dual connectivity configured, and when the MCG failure information function is enabled and CHO is configured at the same time. Consider a scenario where, when RLF or HOF occurs, the UE first attempts to execute the MCG failure information process to restore the link, and before receiving a response message from the network side, the UE detects that the CHO execution condition is met. This embodiment provides a solution to the UE behavior in this scenario, so that the UE can determine whether to continue to execute the MCG failure information process and wait for the response message from the network side, or to execute CHO to switch to the target candidate cell where the execution condition is met.

[0089] Step 1: UE initiates the MCG failure information procedure.

[0090] Step 2: The UE stops the ongoing evaluation / monitoring of CHO execution conditions. Preferably, step 2 is performed during the initialization phase of the MCG Failure Information procedure. Alternatively, the UE may perform step 2 before initiating the MCG Failure Information procedure after RLF / HOF failure.

[0091] If the UE has a saved CHO configuration, it executes step 2.

[0092] Example 7

[0093] This embodiment provides a method for restoring a link when an MCG RLF occurs in a UE configured with dual connectivity, and the MCG failure information function is enabled and CHO is configured. This embodiment is similar to the scenario in Example 6. In this embodiment, the UE terminates the ongoing MCG failure information process and executes the triggered CHO.

[0094] Step 1: The UE initiates the MCG failure information procedure. In this procedure, the UE starts T316 and suspends MCG transmission.

[0095] Step 2: UE triggers a CHO. When the CHO execution conditions of a monitored / assessed CHO candidate cell are met, the UE triggers CHO to the cell.

[0096] Step 3: UE stops T316. When initiating CHO, UE stops T316 in the initial stage of CHO. This step also includes UE resuming MCG transmission.

[0097] The T316 is used to monitor the MCG failure information process as described in the background section. Preferably, the MCG transmission is the MCG transmission corresponding to all SRBs and DRBs.

[0098] Example 8:

[0099] In this embodiment, when the UE performs CHO, it always completes an MCG failure information process before performing CHO. This embodiment is the same as the scenario of embodiment 7, except for the description.

[0100] Step 1: UE triggers a CHO. The UE triggers CHO to a CHO candidate cell when the CHO execution conditions of the cell monitored / assessed are met.

[0101] Step 2: If T316 is in progress, the UE stops T316. Preferably, the UE stops T316 in the initial stage of CHO when initiating CHO. This step also includes the UE resuming MCG transmission.

[0102] As described in the background section, T316 is used to monitor the MCG failure information process. Preferably, the MCG transmission is the MCG transmission corresponding to all SRBs and DRBs. When initiating CHO, it refers to the CHO configuration saved by the UE application.

[0103] Example 9

[0104] This embodiment is the same as the scenario of embodiment 7, except that when CHO is triggered in the MCG failure information process, the UE ignores the triggered CHO, that is, the UE does not execute the triggered CHO.

[0105] Step 1: UE initiates the MCG failure information procedure.

[0106] Step 2: UE triggers a CHO. When the CHO execution conditions of a monitored / assessed CHO candidate cell are met, the UE triggers CHO to the cell.

[0107] Step 3: Ignore the triggered CHO and do not execute the triggered CHO.

[0108] This embodiment can also be expressed as follows: when a CHO is triggered, if T316 is not running (i.e., there is no ongoing MCG failure information process), the UE performs the triggered CHO. Alternatively, when a CHO is triggered, if T316 is running (i.e., there is an ongoing MCG failure information process), the UE does not perform the triggered CHO.

[0109] T316 is running, which can also be expressed as MCG transmission is suspended.

[0110] The above embodiments 6 to 9 are also applicable to the CHO scenario of PSCell, that is, the UE has a saved CHO configuration for the PSCell. In this case, the CHO initiation / triggering refers to the CHO initiation / triggering corresponding to the PSCell.

[0111] In the embodiments of the present disclosure, even if not explicitly stated, CHO-related operations performed by the UE, such as initiating CHO or performing a CHO recovery process on the UE, should be understood to include, before the UE performs the operation: the UE receives an RRC reconfiguration message containing a CHO configuration and a CHO execution condition from a source cell, saves the CHO configuration, and starts monitoring whether the CHO execution condition is satisfied according to the CHO execution condition contained in the RRC message.

[0112] Example 10

[0113] This embodiment describes the user equipment disclosed herein. Figure 5 1 is a block diagram showing the user equipment UE involved in the present invention. Figure 5 As shown, the user equipment UE50 includes a processor 501 and a memory 502. The processor 501 may include, for example, a microprocessor, a microcontroller, an embedded processor, etc. The memory 502 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 memory. The memory 502 stores program instructions. When executed by the processor 501, the instructions may execute the radio link recovery method described in detail in the present invention.

[0114] In the present disclosure, some different embodiments can work together.

[0115] In this disclosure, "base station" refers to a mobile communication data and control exchange center with large transmission power and wide coverage area, including resource allocation scheduling, data reception and transmission and other functions. "User equipment" is

[0116] Refers to user mobile terminals, such as mobile phones, notebooks, and other terminal devices that can communicate wirelessly with base stations or micro base stations.

[0117] The method and related devices of the present disclosure have been described above in conjunction with preferred embodiments. Those skilled in the art will appreciate that the method shown above is merely exemplary. The method of the present disclosure 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 will be developed in the future and can be used for the base station, MME, or UE, etc. The various identifiers shown above are merely exemplary and not restrictive, and the present disclosure 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.

[0118] The program running on the device according to the present disclosure may be a program that controls a central processing unit (CPU) to enable a computer to implement the functions of the embodiments of the present disclosure. The program or the 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.

[0119] The program for realizing each embodiment function of the present disclosure can be recorded on a computer-readable recording medium. The corresponding function 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 short-term dynamic storage program recording medium or any other recording medium that is computer-readable.

[0120] The various features or functional modules of the devices used in the above embodiments can be implemented or executed by circuits (e.g., single-chip 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 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.

[0121] Furthermore, the present disclosure is not limited to the above-described 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.

[0122] As described 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-mentioned 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 modifications can be made to the present disclosure within the scope of the claims, and 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, components with the same effect described in the above-mentioned embodiments can be replaced with each other.

Claims

1. A user equipment (UE), comprising: a receiving circuit configured to receive a radio resource control (RRC) message, the RRC message carrying one or more execution conditions corresponding to a candidate cell; a processor configured to perform execution condition evaluation for conditional reconfiguration based on the one or more execution conditions; as well as Transmitting circuit, where The processor is configured to, when a radio link failure of the master cell group (MCG) is detected when the MCG transmission is not in a suspended state, initiate an MCG failure information procedure to notify the network that the UE has experienced a radio link failure of the MCG. The processor is configured to stop the execution condition evaluation during the MCG failure information, and The sending circuit is configured to send an MCG failure information message in the MCG failure information process.

2. The UE according to claim 1, wherein: The conditional reconfiguration is a conditional switching or a conditional primary / secondary cell (PSCell) change. Regardless of whether the conditional reconfiguration is a conditional switch or a conditional PSCell change, the execution condition evaluation stops during the MCG failure message, and The execution condition evaluation is a measurement event evaluation.

3. A method performed on a user equipment (UE), the method comprising: receiving a radio resource control (RRC) message carrying one or more execution conditions corresponding to a candidate cell; performing an execution condition evaluation for conditional reconfiguration according to the one or more execution conditions; When a radio link failure of the master cell group (MCG) is detected when the MCG transmission is not in a suspended state, an MCG failure information procedure is initiated to notify the network that the UE has experienced a radio link failure of the MCG; Stopping the execution condition evaluation during the MCG failure information process; as well as The MCG failure information message is sent during the MCG failure information process.

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