WO2021115370A1 - 无线链路失败恢复方法以及用户设备 - Google Patents

无线链路失败恢复方法以及用户设备 Download PDF

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Publication number
WO2021115370A1
WO2021115370A1 PCT/CN2020/135182 CN2020135182W WO2021115370A1 WO 2021115370 A1 WO2021115370 A1 WO 2021115370A1 CN 2020135182 W CN2020135182 W CN 2020135182W WO 2021115370 A1 WO2021115370 A1 WO 2021115370A1
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Prior art keywords
cho
configuration
cell
handover
mcg
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PCT/CN2020/135182
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English (en)
French (fr)
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常宁娟
刘仁茂
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夏普株式会社
常宁娟
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Priority to US17/783,714 priority Critical patent/US20230022967A1/en
Publication of WO2021115370A1 publication Critical patent/WO2021115370A1/zh

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H04W36/0055—Transmission or use of information for re-establishing the radio link
    • H04W36/0079—Transmission or use of information for re-establishing the radio link in case of hand-off failure or rejection
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W76/00—Connection management
    • H04W76/10—Connection setup
    • H04W76/18—Management of setup rejection or failure
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W76/00—Connection management
    • H04W76/10—Connection setup
    • H04W76/19—Connection re-establishment
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H04W36/0055—Transmission or use of information for re-establishing the radio link
    • H04W36/0069—Transmission or use of information for re-establishing the radio link in case of dual connectivity, e.g. decoupled uplink/downlink
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/08—Reselecting an access point
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/24—Reselection being triggered by specific parameters
    • H04W36/30—Reselection being triggered by specific parameters by measured or perceived connection quality data
    • H04W36/305—Handover due to radio link failure

Definitions

  • the present disclosure relates to the field of wireless communication technology, and more specifically, the present disclosure relates to a recovery method after a wireless link failure and corresponding user equipment.
  • Non-Patent Document: RP-181433 New WID on NR (New Radio) mobility enhancements.
  • LTE Long Term Evolution
  • Non-Patent Document: RP-190272 WID for Even further Mobility enhancement in E-UTRAN (Evolved-Universal Terrestrail Radio Access Network) )).
  • One of the research goals of these two projects is to find one of the mobility needs in the network: seamless handover, that is, the handover interruption time of 0 milliseconds or close to 0 milliseconds can be met during the cell handover, and the handover can be enhanced. Robustness reduces the handover failure rate.
  • CHO Conditional Handover
  • the base station issues a handover command to the UE in advance, and the handover command contains conditional configuration information.
  • the UE performs handover according to the handover command received before when the configured condition is met. In this way, the early issuance of the handover command can increase the success rate of handover command reception, thereby improving the handover success rate, and avoiding the delay caused by the handover failure caused by the failure of the handover command reception to service interruption.
  • the present disclosure proposes solutions to some problems of implementing CHO in the NR system and the LTE system.
  • the purpose of the embodiments of the present disclosure is to propose a solution to the problem of implementing the CHO technology in the NR system and the LTE system. More specifically, the present disclosure proposes a solution to the problem of how to use the saved CHO configuration to restore the link connection when the wireless link fails.
  • the embodiments of the present disclosure provide a wireless link failure recovery method and corresponding user equipment that are executed when a handover failure occurs in a user equipment.
  • a method for recovering from a radio link failure including: a user equipment UE detects that a handover failure occurs; when the UE has a saved condition-based handover CHO configuration, or the UE When there is a saved condition-based handover CHO configuration and CHO recovery is enabled, the UE falls back to the configuration used by the source cell.
  • the configuration used by the source cell includes physical layer dedicated configuration and media access control One or more of MAC layer configuration and semi-static SPS configuration.
  • the UE when the UE does not have a saved CHO configuration or CHO recovery is not enabled, the UE may fall back to a configuration other than physical layer dedicated configuration and MAC layer configuration. And/or the configuration used in the source cell other than the SPS configuration.
  • the handover failure may include: the UE fails to perform CHO and the UE fails to perform non-CHO.
  • the UE may further include: the UE performs a CHO recovery process, in the cell selection process of the CHO recovery process, in the case that the selected cell is a CHO candidate cell
  • the UE applies the saved CHO configuration to execute CHO to the CHO candidate cell, and in the case that the selected cell is not the CHO candidate cell, the UE initiates a radio resource control RRC connection re-establishment process.
  • the UE in the initialization phase of initiating the CHO recovery process, may perform the following operations: when the timer T310 is running, stop the timer T310; When the timer T312 associated with the primary cell group MCG is running, the timer T312 is stopped.
  • a method for recovering from a radio link failure including: a user equipment UE detects that a handover failure has occurred; and the UE falls back to a configuration other than physical layer dedicated configuration, media access control MAC layer configuration, and/ Or the configuration used in the source cell other than the semi-static SPS configuration; and the UE performs the condition-based handover CHO recovery process.
  • 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.
  • the UE may initiate a radio resource control RRC connection re-establishment process.
  • the UE may perform the transfer to the all CHO based on the configuration after the fallback and applying the saved CHO configuration.
  • the CHO of the CHO candidate cell in the case that the selected cell is the CHO candidate cell, the UE may perform the transfer to the all CHO based on the configuration after the fallback and applying the saved CHO configuration.
  • the UE in the initialization phase of initiating the CHO recovery process, may perform the following operations: when the timer T310 is running, stop the timer T310; When the timer T312 associated with the primary cell group MCG is running, the timer T312 is stopped.
  • a user equipment including: a processor; and a memory storing instructions; wherein the instructions execute the wireless link failure recovery according to the context when the instructions are run by the processor method.
  • FIG. 1 is a sequence diagram showing that a user equipment UE in a connected state changes a serving cell through a handover process.
  • Fig. 2 is a schematic diagram showing the flow of condition switching.
  • FIG. 3 is a flowchart showing the wireless link recovery based on conditional switching in the first embodiment.
  • Fig. 4 is a flowchart showing the wireless link recovery based on conditional switching in the second embodiment.
  • FIG. 5 shows a block diagram of the user equipment UE involved in the present disclosure.
  • LTE Long Term Evolution
  • NR New Radio Access
  • E-UTRA Evolved Universal Terrestrial Radio Access
  • handover refers to the change of the primary cell (Primary Cell, PCell) initiated by the network side. It includes the change of the primary cell between cells and the change of the primary cell 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 may be the same cell or different cells.
  • the secret key or security algorithm used for access layer security can also be updated accordingly.
  • the source cell is also called a source base station, and it can also be a source beam (beam) or a source transmission point (TRP).
  • the target cell can also be called a target base station, or it can be a target beam or a target transmission point.
  • the source cell refers to the cell that is connected to serve 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 the UE connects to and serves the UE after the handover process is successfully completed, or the cell indicated by the target cell identifier included in the handover command, and the cell that the UE accesses when the handover is received.
  • the handover command described in the present disclosure is used to trigger the UE to perform handover.
  • it is an RRC reconfiguration message containing a synchronization reconfiguration (Reconfigurationwithsync) information element.
  • MCG master cell group
  • the RRC reconfiguration message of the reconfiguration (Reconfigurationwithsync) information element can also be referred to as synchronous reconfiguration.
  • handover can also be referred to as synchronous reconfiguration.
  • the synchronization reconfiguration information element or the mobile control information information element contains the configuration information of the target cell, such as the target cell identity, the target cell frequency, the common configuration of the target cell, such as system information, and the random information used by the UE to access the target cell. Access configuration, UE's security parameter configuration in the target cell, UE's radio bearer configuration in the target cell, etc.
  • the embodiments of the present disclosure may also be applicable to the handover or change of primary and secondary cells (Primary Secondary Cell, PSCell).
  • PSCell refers to the serving cell where the UE performs the random access process or the initial physical uplink shared channel (PUSCH) transmission during the change or addition of the secondary cell group in the secondary cell group (SCG, Secondary Cell Group) .
  • SCG Secondary Cell Group
  • PCell and PSCell are collectively referred to as special cell (Special Cell, SpCell).
  • the RRC reconfiguration message in the present disclosure is equivalent to the RRC connection reconfiguration message; similarly, the response message RRC reconfiguration complete message is equivalent to the RRC connection reconfiguration complete message.
  • the RRC connection re-establishment request message is equivalent to the RRC re-establishment request message, and the RRC re-establishment message is equivalent to the RRC connection re-establishment message; in the same way, the response message RRC re-establishment complete message is equivalent to the RRC connection re-establishment complete message.
  • the handover command is equivalent to the RRC message containing the handover command, and refers to the RRC message or the configuration in the RRC message that triggers the UE to perform the handover.
  • Switch configuration refers to all or part of the configuration in the switch command. Cancel, release, delete, empty and clear can be replaced. Execution, use and application can be replaced. Configuration and reconfiguration can be replaced. Links and connections can be replaced. Monitor and detect can be replaced. The conditional switching command and the conditional switching configuration can be replaced.
  • the UE after the UE receives a radio resource control (Radio Resource Control, RRC) message containing a handover command, it can still maintain the communication with the source base station, including data transmission, before initiating the handover process, so as to further reduce the interruption of data transmission. time.
  • RRC Radio Resource Control
  • FIG. 1 is a sequence diagram showing that a user equipment UE in a connected state changes a serving cell through a handover process.
  • the handover process generally includes the following stages:
  • Phase 1 Measurement phase.
  • the base station sends the measurement configuration to the user equipment (User Equipment, UE); the UE measures the radio link corresponding to the serving cell or neighboring cell based on the measurement configuration, and when the configured measurement reporting conditions are met, the UE sends the measurement to the base station report.
  • the measurement phase is not necessary, and the UE can be handed over blindly when the base station does not have a valid measurement report.
  • 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 the load of the base station. 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 according to the UE context in the handover request message and the available resources of the target base station. If accepted, it will reply to the source base station with a handover confirmation message, where the handover confirmation message contains a base station Inter-node RRC messages are handover commands.
  • Phase 3 Switch execution phase.
  • the source base station issues the handover command to the UE and starts to forward 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 handover, accesses the target base station through a random access process, and sends a confirmation message to the target base station. Among them, the random access process is not necessary.
  • Phase 4 The handover is completed. After the target base station confirms that the UE has successfully accessed, it sends a handover complete message to the source base station. According to this, the source base station can release the UE context stored on it.
  • Fig. 2 is a schematic diagram showing the flow of condition switching.
  • a relatively conservative measurement report threshold is set so that the base station obtains the measurement result in advance, and performs handover preparation in advance based on the measurement result and the selected target base station, so that the base station can perform handover conditions under real handover conditions (relative to the conservative Before the measurement report threshold is met, the handover command RRC message containing the CHO candidate cell and the corresponding CHO execution condition is issued to the UE in advance.
  • the RRC message (the RRC connection reconfiguration message in the LTE system) supports more than one CHO candidate cell and the CHO configuration corresponding to each CHO candidate cell (that is, the RRC connection reconfiguration message included in the RRC connection reconfiguration message configured by the candidate target cell). Configuration) and CHO execution conditions.
  • the UE After the UE receives the conditional handover command, it does not immediately perform the handover, but saves the received CHO configuration (that is, the configuration included in the RRC reconfiguration message configured by the target cell), and according to the handover command message carried
  • the CHO execution condition corresponding to the CHO candidate cell starts to monitor the link quality of the source cell or the link quality of the target cell to evaluate whether the CHO execution condition is met. Only when it is monitored that one or more of the configured CHO execution conditions are met, the UE starts to perform handover according to the saved CHO configuration and accesses the target cell.
  • the UE directly applies the CHO configuration to switch to the target cell, that is, the CHO configuration and the source cell configuration Irrelevant. 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 execution of the handover, the UE will stop evaluating the configured CHO execution conditions. In short, conditional switching refers to a switching process that is executed only when one or more configured CHO execution conditions are met.
  • the CHO execution condition may be a measurement event, for example, the condition is measurement event A3 (the signal quality of the neighboring cell is better than the serving cell for a period of time by more than an offset).
  • the neighboring cell corresponds to the CHO candidate target cell.
  • One CHO candidate cell can correspond to one or more than one CHO execution conditions. When multiple CHO execution conditions are configured for a candidate cell, the UE starts to perform the corresponding handover only when all CHO execution conditions are met.
  • 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 CHO switching command as CHO execution conditions.
  • Radio Link Failure Radio Link Failure
  • HOF Handover Failure
  • Case 1 The timer T310 used for radio link failure detection expires.
  • the RRC layer of the UE detects the physical layer problem of the primary cell Pcell, it receives N310 consecutive out-of-sync indications from the bottom layer, and at this time the timer T300 used for RRC process control (using When detecting the RRC connection establishment process), T301 (used to detect the RRC connection re-establishment process), T304 (used to detect the handover process) or T311 (used to detect the cell selection phase in the RRC connection re-establishment process) is not running, Start T310.
  • N310 is a constant configured by the network side. If the constant is not configured on the network side, the UE uses a predefined default value.
  • T312 is used for wireless link failure detection when the measurement report is triggered.
  • the RRC layer of the UE triggers a measurement report whose trigger type is set to event trigger and is configured with a measurement ID that can use T312, if T310 is running, the corresponding T312 is activated.
  • T312 is activated when one of the following conditions is met: Condition 1: For a measurement ID, if the trigger type is set to event, and for one or more applicable cells When all the measurements that have been filtered by Layer 3 meet the entry conditions applied to the event within the timetoTrigger time, and the measurement report list (VarMeasReportList) saved by the UE does not contain any measurement report items for the measurement identifier If the UE supports T312 and the event configuration includes the configuration available for T312 (useT312 information element), if T310 is running, if T312 is not running, T312 is started.
  • T312 For a measurement ID (measurement ID), if the trigger type is set to event, and for one or more applicable cells that are not included in the cellsTriggeredList (cellsTriggeredList), all measurements that have been filtered by layer 3 The entry condition applied to the event is met within the timetoTrigger time. If the UE supports T312 and the configuration of the event includes the configuration available for T312 (useT312 information element), if T310 is running, if T312 is not running, start T312. The value of T312 adopts the value of T312 configured by the network side for the measurement object (measurement object) associated with the measurement identifier.
  • Case 3 A random access failure indication from the Medium Access Control (MAC) layer is received and the timers T300, T301, T304, or T311 used for RRC process control are not running at this time.
  • the MAC refers to the MAC corresponding to the MCG.
  • Case 4 An indication from the Radio Link Control (RLC) layer corresponding to the MCG is received, and the indication is used to indicate a signaling radio bearer (Signaling Radio Bearer, SRB) or data radio bearer (Data Radio bearer). Bearer, DRB)
  • SRB Signaling Radio Bearer
  • DRB Data Radio bearer
  • the UE judges the occurrence of HOF according to the timer T304 that detects the handover process.
  • the UE starts T304 when it starts to perform a handover, and applies the corresponding RRC configuration in the handover command, and stops T304 when the handover is successfully completed. If T304 timeout occurs, the UE considers that HOF has occurred. After HOF, the UE falls back to the configuration used in the source cell before the handover was performed.
  • 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 (refers to the configuration in the sps-config information element).
  • the UE initiates an RRC connection re-establishment process to reestablish/restore the connection with the network side.
  • RLF Radio Link Failure
  • HOF Handover process failure
  • 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.
  • the UE When the UE receives the response message that is the 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 the RRC connection re-establishment complete message to the base station, and successfully ends the RRC connection re-establishment process.
  • the re-established cell refers to a cell used by the UE to send an RRC connection re-establishment request message and receive a corresponding response message for re-establishing an 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.
  • stop T311 if T311 times out, the UE cannot select a suitable cell.
  • the UE is out of coverage, and the UE will Leave the RRC connected state and enter the RRC idle state or RRC inactive state (RRC_Inactive).
  • a conditional handover scenario from the moment when the UE receives and saves a CHO configuration to the time when the corresponding CHO condition is satisfied 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 implementation of the CHO procedure during RLF/HOF: When RLF or HOF occurs, the UE first selects a cell to perform link recovery through the cell selection process.
  • the selected cell is a CHO candidate cell (that is, the cell corresponds to the 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 passes Sending an RRC connection establishment request to the selected cell to try to restore the connection with the network side is to adopt the traditional RRC connection re-establishment process.
  • This enhancement of the link recovery mechanism is referred to as the CHO configuration-based link failure recovery mechanism (referred to as the CHO link recovery mechanism for short) in this disclosure.
  • the serving cell enables the CHO link recovery function of the UE through the enable indication in the RRC signaling.
  • the UE can only perform CHO recovery once after RLF/HOF occurs. That is to say, if the CHO executed in the CHO recovery process fails, the UE directly enters the idle state; in another implementation manner, the UE directly triggers the RRC re-establishment process.
  • 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 (that is, the link connection is restored through the RRC connection re-establishment process), and is also called the MCG failure information process.
  • the purpose of this procedure is to notify the primary base station that an MCG radio link failure has occurred in the UE.
  • the UE For a UE configured with split SRB1 or SRB3, when the UE's MCG detects RLF, if the UE's MCG and SCG are not suspended and the fast MCG link recovery function is configured, Then the UE initiates the MCG failure information process, and reports the MCG link failure information to the primary base station via the SCG link in the MCG failure information RRC message.
  • the primary 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 MCG failure information process.
  • the UE starts T316 when sending an MCG failure information RRC message; when MCG transmission resumes or receives a response from the network side (such as an RRC release message or an RRC reconfiguration message for instructing UE handover) or initiates an RRC re-establishment process, it stops T316 ; If T316 times out, the UE considers that the MCG failure information process is over, and initiates the RRC re-establishment process for MCG link recovery.
  • the fast MCG link recovery mechanism can be applied to the situation 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.
  • MR-DC Multi-Radio access technology Dual Connectivity
  • 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
  • the present disclosure mainly proposes a solution to the problem of how to recover the UE configured with CHO during RLF/HOF and the connection problem on the network side. More specifically, how to apply the saved CHO configuration to switch to the target cell during HOF; how to avoid recurring radio link failure during an ongoing CHO link recovery process; or configure the CHO recovery mechanism and the UE at the same time
  • the problem of how to coordinate the two link recovery mechanisms to recover the link is a problem that this disclosure focuses on and solves.
  • This embodiment is executed on the UE, and further executed on the RRC layer of the UE.
  • the UE fails the HOF handover to cell A, it rolls back its RRC configuration to the configuration in the source cell before the handover, but the configuration does not include the physical layer dedicated configuration and MAC configuration, that is to say, the current UE uses The physical layer dedicated configuration and MAC configuration of both are from the configuration of the handover target cell A corresponding to this HOF.
  • the UE may initiate a CHO recovery process to the CHO candidate cell B to restore the link, and the UE uses the CHO candidate cell B in the CHO recovery process
  • the CHO configuration is a delta configuration
  • the physical layer dedicated configuration and MAC layer configuration of cell B applied by the UE are based on the current related configuration (ie, the configuration of cell A)
  • the saved CHO configuration of cell B is not an incremental configuration of the related configuration of cell A. This will make the configuration applied by the network side and the UE inconsistent after the CHO handover, and this mismatched configuration can lead to further configuration/link failure.
  • This embodiment provides a solution based on this problem.
  • the UE that can perform CHO recovery to recover the link when a HOF occurs, by falling back to the configuration of the source cell before the handover, the physical layer dedicated configuration or the MAC layer dedicated configuration will enable the UE to perform subsequent CHO recovery.
  • the saved incremental configuration of the CHO candidate cell is applied based on the configuration of the source cell before the handover, so as to maintain the consistency of the RRC configuration with the network side after the handover.
  • FIG. 3 is a flowchart showing wireless link recovery based on conditional switching in Embodiment 1.
  • an example of a wireless link failure recovery method based on conditional switching includes the following steps.
  • Step 1 The UE detects that a handover failure has occurred (T304 timeout).
  • the handover failure is the failure of the UE to perform traditional non-CHO handover, or the failure of the UE to perform CHO.
  • the traditional non-CHO handover failure means that the UE immediately applies the received configuration to perform handover to the target cell after receiving the RRC reconfiguration message containing the handover command, including handover without random access (the handover command is configured with rach- skip), make-before-break (MBB) switch (makebeforebreak is configured in the switch command), and dual-active protocol stack (DAPS) switch (refers to During the handover process after the RRC message, the connection with the source cell is maintained until the target cell is successfully accessed, and the source cell is not released until the RRC message contains the DAPS handover configuration indication/enable).
  • MBB make-before-break
  • DAPS dual-active protocol stack
  • Step 2 If the UE has a saved CHO configuration, or when the UE has a saved CHO configuration and CHO recovery is enabled, when HOF occurs in step 1, the UE falls back to the configuration used by the source cell. Specifically, when the UE is enabled with CHO recovery by default, if the UE has a saved CHO configuration, the UE will fall back to the configuration used by the source cell when HOF occurs. In addition, if the UE is not enabled with CHO recovery by default, if the UE has a saved CHO configuration and CHO recovery is enabled, the UE will fall 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 physical layer dedicated configuration, MAC layer configuration, and SPS configuration.
  • the CHO recovery enabled means that the CHO recovery enable indication (such as the attemptCHO information element is used to identify) or the CHO recovery enable indication is configured in the RRC message containing the CHO configuration received by the UE. Is set to "TURE" or "1".
  • the CHO recovery enable indication is used to allow the UE to recover the link by executing CHO if the selected cell is a CHO candidate cell after the link fails.
  • the specific definition is: if it exists in the RRC message, then in the first cell selection process after the link failure, if the selected cell is a CHO candidate cell, the UE performs CHO to the cell.
  • Another way to describe the operation described in this step is: when a handover fails, if the UE has a saved CHO configuration, or the UE has a saved CHO configuration and CHO recovery is enabled, the UE will fall back to the source cell. Configuration used; otherwise, if the UE has no saved CHO configuration or CHO recovery is not enabled, it will fall back to the configuration used in the source cell except for the physical layer dedicated configuration, MAC layer configuration and/or SPS configuration.
  • Step 3 The UE performs the CHO recovery process, including: the UE performs a cell selection process. If the selected (suitable) cell is a CHO candidate cell, the UE applies the CHO configuration saved in the cell and executes the CHO to the cell; Otherwise, the UE initiates the RRC connection re-establishment process. The UE applies the saved CHO configuration based on the configuration after the UE rollback in step 2. Step 3 is optional.
  • this embodiment also includes before step 1: the UE receives the RRC reconfiguration message containing the CHO configuration and the CHO execution condition from the source cell, saves the CHO configuration, and starts according to the CHO execution condition contained in the RRC message Monitoring whether the CHO execution conditions are met. Before HOF in step 1, it may also include the UE performing a handover to the target base station.
  • the saved CHO configuration of the UE can also be described as the UE configured with CHO.
  • the source cell is a source PCell.
  • 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 Embodiment 1, and is used to maintain the consistency of the RRC configuration with the network side after the CHO recovery process performed after the handover fails.
  • This embodiment is different from Embodiment 1 in that the UE rolls back its physical layer configuration during the CHO recovery process to the corresponding configuration used by the source cell before the handover failure, so as to ensure that the UE can correctly apply the selected cell configuration. The corresponding saved CHO configuration is switched.
  • FIG. 4 is a flowchart showing the wireless link recovery based on conditional handover in Embodiment 2.
  • another example of a wireless link failure recovery method based on conditional handover includes the following steps.
  • Step 1 The UE fails to handover (T304 timeout).
  • the handover failure is the failure of the UE to perform traditional non-CHO handover, or the failure of the UE to perform CHO.
  • the traditional non-CHO handover failure means that the UE immediately applies the received configuration after receiving the RRC reconfiguration message containing the handover command to perform handover to the target cell, including no random access handover, MBB handover, and DAPS handover.
  • 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.
  • Step 3 The UE performs the 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: fall back to the physical layer used in the source cell Dedicated configuration, MAC layer configuration and/or SPS configuration, and apply the saved CHO configuration of the cell based on the current configuration, and execute the CHO to the cell; otherwise, if the selected cell is not a CHO candidate cell, the UE initiates an RRC connection Re-establish the process.
  • the application of the CHO configuration saved for the cell based on the current configuration refers to applying the saved CHO configuration on the basis of the RRC configuration after the UE rollback in step 2 and step 3.
  • the UE executes step 3 only when there is a saved CHO configuration and CHO recovery is enabled.
  • the enabled CHO recovery is described in Example 1, which will not be repeated here.
  • this embodiment also includes before step 1: the UE receives the RRC reconfiguration message containing the CHO configuration and the CHO execution condition from the source cell, saves the CHO configuration, and starts according to the CHO execution condition contained in the RRC message Monitoring whether the CHO execution conditions are met. Before HOF in step 1, it may also include the UE performing a handover to the target base station.
  • the saved CHO configuration of the UE can also be described as the UE configured with CHO.
  • the source cell is a source PCell.
  • 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 Embodiment 1, and is used to maintain the consistency of the RRC configuration with the network side after the CHO recovery process performed after the handover fails.
  • This embodiment is different from Embodiment 1 in that the UE does not fall back its physical layer configuration, etc., to the corresponding configuration used by the source cell before the handover failure occurred during the CHO recovery process, and uses the corresponding system default configuration to ensure The UE can correctly apply the saved CHO configuration corresponding to the selected cell to perform handover.
  • Step 1 The UE fails to handover (T304 timeout).
  • the handover failure is the failure of the UE to perform traditional non-CHO handover, or the failure of the UE to perform CHO.
  • the traditional non-CHO handover failure means that the UE immediately applies the received configuration after receiving the RRC reconfiguration message containing the handover command to perform handover to the target cell, including no random access handover, MBB handover, and DAPS handover.
  • 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.
  • Step 3 The UE performs the 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: Apply the system default physical layer dedicated configuration and default MAC Layer configuration and/or default SPS configuration, and apply the saved CHO configuration of the cell based on the current configuration, and execute the CHO to the cell; otherwise, if the selected cell is not a CHO candidate cell, the UE initiates the 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 on the basis of the RRC configuration after the UE rollback in step 2 and the system default configuration applied in step 3.
  • the UE executes step 3 only when there is a saved CHO configuration and CHO recovery is enabled.
  • CHO recovery refer to the description in Embodiment 1, which will not be repeated here.
  • Step 4 When the UE executes the CHO of the selected cell during the CHO recovery process, it sends an indication message to the target cell.
  • the indication information is used to indicate that this CHO was initiated due to a link failure (HOF). Furthermore, the indication information is used to indicate that the UE in the CHO this time applies the system default physical layer dedicated configuration, MAC layer configuration or SPS configuration.
  • the indication information may 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 as a MAC control element (MAC CE).
  • MAC CE MAC control element
  • RRC message handover response message (RRC connection reconfiguration generated during T304 operation and sent to the target cell)
  • MAC CE MAC CE or RRC in the first PUSCH after the handover is successful
  • the success of the handover may be the successful completion of the random access procedure, for example, the RRC layer receives a successful completion indication of the random access procedure from the MAC layer.
  • this embodiment also includes before step 1: the UE receives the RRC reconfiguration message containing the CHO configuration and the CHO execution condition from the source cell, saves the CHO configuration, and starts according to the CHO execution condition contained in the RRC message Monitoring whether the CHO execution conditions are met. Before HOF in step 1, it may also include the UE performing a handover to the target base station.
  • the saved CHO configuration of the UE can also be described as the UE configured with CHO.
  • the source cell is a source PCell.
  • 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 Embodiment 3, and is used to resolve the consistency of the RRC configuration with the network side after the CHO recovery process performed after the handover fails.
  • This embodiment is different from Embodiment 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 due to the chain Triggered by road failure. In this way, the network side keeps the physical layer dedicated configuration, MAC layer configuration or SPS configuration consistent with the UE, so as to ensure that the UE can correctly apply the saved CHO configuration corresponding to the selected cell to perform handover.
  • Step 1 The UE receives the RRC reconfiguration message containing the CHO configuration and the CHO execution condition from the source cell, saves the CHO configuration, and starts to monitor whether the CHO execution condition is met according to the CHO execution condition contained in the RRC message.
  • Step 2 UE executes CHO.
  • the UE performs the following operations: applying the default physical layer dedicated configuration, MAC configuration or SPS configuration of the system; applying the saved CHO configuration corresponding to the target cell.
  • the CHO configuration is an enhanced configuration based on the current UE configuration.
  • the CHO configuration does not include a full configuration indication.
  • the UE performs the operation in step 2 only when CHO recovery is enabled.
  • CHO recovery refer to the description in Embodiment 1, which will not be repeated here.
  • the saved CHO configuration of the UE can also be described as the UE configured with CHO.
  • the source cell is a source PCell.
  • 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 saved by the UE is always based on the system default corresponding configuration of. That is to say, the above-mentioned configuration in the CHO configuration configured by the target candidate cell is always based on the incremental configuration of the corresponding configuration defaulted by the system.
  • the monitoring timers currently used to trigger RLF include T310 and T312.
  • the trigger conditions of these two timers are different, and they can be running at the same time.
  • RLF will be triggered, while the other timer is still running.
  • the other running timer expires at this time, it will cause the UE to enter the RLF state again , Thus re-execute a CHO recovery process, which will extend the time of link interruption and affect the continuity of service.
  • the UE if the UE enters a CHO recovery process, the UE will stop the running RLF related timer to avoid the occurrence of the above situation and shorten the link interruption time.
  • Step 1 RLF occurs on the UE. If the timeout occurs at T310 or T312, the UE declares RLF.
  • Step 2 The UE initiates the CHO recovery process.
  • the UE performs the following operations: if there is a running T310, stop T310; if there is a T312 associated with a running MCG, stop the T312.
  • the initialization phase of initiating the CHO recovery process refers to before initiating the cell selection process.
  • the UE performs the operation of stopping the timer.
  • the UE executes step 2 only when there is a saved CHO configuration and CHO recovery is enabled. The enabled CHO recovery is described in Example 1, which will not be repeated here.
  • Step 3 The UE executes the CHO recovery process.
  • the CHO recovery process is as mentioned before, so I won’t repeat it here.
  • This embodiment provides a method for recovering the link when the RLF of the MCG occurs when the UE is configured with dual connectivity, and the MCG failure information function is enabled and the CHO is configured at the same time.
  • the UE When RLF or HOF occurs, the UE first tries to perform the MCG failure information process to restore the link, and before receiving the response message from the network side, the UE detects that the CHO execution condition is satisfied.
  • This embodiment provides a solution to the UE behavior in this scenario, so that the UE can determine whether to continue to perform the MCG failure information process and wait for a response message from the network side, or perform CHO handover to the target candidate cell where the execution condition is satisfied.
  • Step 1 The UE initiates the MCG failure information process.
  • Step 2 The UE stops the evaluation/monitoring of the CHO execution condition being executed.
  • step 2 is performed during the initialization phase of the MCG failure information process.
  • the UE may perform step 2 before initiating the MCG failure information procedure after RLF/HOF failure.
  • the UE executes step 2 when there is a saved CHO configuration.
  • This embodiment provides a method for recovering the link when the RLF of the MCG occurs when the UE is configured with dual connectivity, and the MCG failure information function is enabled and the CHO is configured at the same time.
  • the scenario in this embodiment is the same as that in the sixth embodiment.
  • the UE ends the ongoing MCG failure information process and executes the triggered CHO.
  • Step 1 The UE initiates the MCG failure information process. During this process, the UE starts T316 and suspends MCG transmission.
  • Step 2 The UE triggers a CHO.
  • the UE triggers the CHO of a CHO candidate cell when the CHO execution condition of a CHO candidate cell is satisfied by monitoring/evaluating the cell.
  • Step 3 UE stops T316.
  • the UE executes the initial phase stop T316 of CHO. This step also includes that the UE resumes MCG transmission.
  • the T316 is used to monitor the process of MCG failure information as described in the background section.
  • the MCG transmission is MCG transmission corresponding to all SRBs and DRBs.
  • Step 1 The UE triggers a CHO.
  • the UE triggers the CHO of a CHO candidate cell when the CHO execution condition of a CHO candidate cell is satisfied by monitoring/evaluating the cell.
  • Step 2 If there is a running T316, the UE stops T316. Preferably, the UE executes the initial phase stop T316 of CHO when it initiates CHO. This step also includes that the UE resumes MCG transmission.
  • the T316 is used to monitor the process of MCG failure information as described in the background section.
  • the MCG transmission is MCG transmission corresponding to all SRBs and DRBs.
  • the CHO refers to the CHO configuration saved by the UE application.
  • This embodiment is the same as the scenario of Embodiment 7, except that when CHO is triggered during the MCG failure information process, the UE ignores the triggered CHO, that is, the UE does not execute the triggered CHO.
  • Step 1 The UE initiates the MCG failure information process.
  • Step 2 The UE triggers a CHO.
  • the UE triggers the CHO of a CHO candidate cell when the CHO execution condition of a CHO candidate cell is satisfied by monitoring/evaluating the cell.
  • Step 3 Ignore the triggered CHO, and do not execute the triggered CHO.
  • This embodiment can also be expressed as that when a CHO is triggered, if T316 is not running (that is, there is no ongoing MCG failure information process), the UE executes the triggered CHO. Or, when a CHO is triggered, if T316 is running (that is, there is a running MCG failure information process), the UE does not execute the triggered CHO.
  • T316 is running, which can also be expressed as MCG transmission is suspended.
  • the foregoing embodiments 6 to 9 are also applicable to the CHO scenario of the PSCell, that is, the UE has a saved CHO configuration for the PSCell.
  • the CHO initiation/triggering at this time refers to the CHO initiation/triggering corresponding to the PSCell.
  • the CHO-related operations performed by the UE such as initiating the CHO or the UE performing the CHO recovery process on the UE, even if it is not explicitly stated, should also be understood to include before the UE performs the operation: the UE receives from the source cell The RRC reconfiguration message containing the CHO configuration and the CHO execution condition is saved, the CHO configuration is saved, and the CHO execution condition contained in the RRC message is started to monitor whether the CHO execution condition is met.
  • FIG. 5 is a block diagram showing a user equipment UE related to the present invention.
  • 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, and the like.
  • the memory 502 may include, for example, volatile memory (such as random access memory RAM), hard disk drive (HDD), non-volatile memory (such as flash memory), or other memories.
  • the memory 502 stores program instructions. When the instruction is run by the processor 501, it can execute the above-mentioned wireless link recovery method described in detail in the present invention.
  • base station refers to a mobile communication data and control switching center with larger transmission power and wider coverage area, including functions such as resource allocation and scheduling, data reception and transmission.
  • User Equipment is a mobile communication data and control switching center with larger transmission power and wider coverage area, including functions such as resource allocation and scheduling, data reception and transmission.
  • user mobile terminals such as mobile phones, notebooks, and other terminal devices that can communicate with base stations or micro base stations wirelessly.
  • the method and related equipment of the present disclosure have been described above in conjunction with preferred embodiments. Those skilled in the art can understand that the method shown above is only 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, may also include modules that can be developed or developed in the future that can be used for base stations, MMEs, or UEs, and so on.
  • the various identifiers shown above are only exemplary rather than restrictive, and the present disclosure is not limited to specific information elements as examples of these identifiers. Those skilled in the art can make many changes and modifications based on the teaching of the illustrated embodiment.
  • the program running on the device may be a program that causes the 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 volatile memory (such as random access memory RAM), hard disk drive (HDD), non-volatile memory (such as flash memory), or other memory systems.
  • the program for realizing the functions of the various embodiments of the present disclosure may be recorded on a computer-readable recording medium.
  • Corresponding functions can be realized by causing the computer system to read the programs recorded on the recording medium and execute these programs.
  • the so-called "computer system” herein may be a computer system embedded in the device, and may include an operating system or hardware (such as peripheral devices).
  • the "computer-readable recording medium” may be a semiconductor recording medium, an optical recording medium, a magnetic recording medium, a recording medium storing a program dynamically for a short period of time, or any other recording medium readable by a computer.
  • circuits for example, single-chip or multi-chip integrated circuits.
  • Circuits designed to perform the functions described in this specification can include general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field programmable gate arrays (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-mentioned circuit can be a digital circuit or an analog circuit. In the case of new integrated circuit technologies that 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.
  • present disclosure is not limited to the above-mentioned embodiments. Although various examples of the embodiment have been described, the present disclosure is not limited thereto.
  • Fixed or non-mobile electronic equipment installed indoors or outdoors can be used as terminal equipment or communication equipment, such as AV equipment, kitchen equipment, cleaning equipment, air conditioners, office equipment, vending machines, and other household appliances.

Abstract

本公开提供了无线链路失败恢复方法以及用户设备。所述无线链路失败恢复方法，包括：用户设备UE检测到发生切换失败；在所述UE有保存的基于条件切换CHO配置的情况下、或者所述UE有保存的基于条件切换CHO配置且被使能了CHO恢复的情况下，所述UE回退到源小区所使用的配置，所述源小区所使用的配置包含物理层专用配置、媒体接入控制MAC层配置和半静态SPS配置中的一种或多种。

Description

无线链路失败恢复方法以及用户设备 技术领域
本公开涉及无线通信技术领域，更具体地，本公开涉及无线链路失败后的恢复方法以及对应的用户设备。
背景技术
2018年6月，在第三代合作伙伴计划(3rd Generation Partnership Project：3GPP)RAN#80次全会上批准了一个5G技术标准的新的研究项目(参见非专利文献：RP-181433：New WID on NR(New Radio)mobility enhancements)。此外，另有一个基于长期演进系统(Long Term Evolution，LTE)的Release 16新研究项目(参见非专利文献：RP-190272：WID for Even further Mobility enhancement in E-UTRAN(Evolved-Universal Terrestrail Radio Access Network))。这两个项目的研究目的之一是找到用于满足网络中的移动性需要之一：无缝切换，即在小区切换过程中能够满足0毫秒或接近0毫秒的切换中断时间，并增强切换的鲁棒性，降低切换失败率。在正在研究的降低切换中断时间和/或增强切换鲁棒性的解决方案中，有一种解决方法称为基于条件的切换(Conditional HandOver，CHO)。在CHO机制中，基站提前下发切换命令给UE，其中切换命令中包含条件配置信息。UE在所配置的条件满足时再根据之前收到的切换命令来执行切换。这样通过切换命令的提前下发可以提高切换命令接收的成功率，从而提高切换成功率，避免因切换命令接收失败而带来的切换失败对业务中断带来的时延。
本公开针对在NR系统和LTE系统中实现CHO的一些问题提出解决方法。
发明内容
本公开实施例的目的在于针对在NR系统和LTE系统中实现CHO技术的问题提出解决方法。更具体地，本公开针对在无线链路失败时如何实现利用已保存的CHO配置来恢复链路连接的问题提出了解决方法。本公开实施例提供了在用户设备发生切换失败的情况下所执行的无线链路失败恢复方法以及相应的用户设备。
根据本公开的第一方面，提出了一种无线链路失败恢复方法，包括：用户设备UE检测到发生切换失败；在所述UE有保存的基于条件切换CHO配置的情况下、或者所述UE有保存的基于条件切换CHO配置且被使能了CHO恢复的情况下，所述UE回退到源小区所使用的配置，所述源小区所使用的配置包含物理层专用配置、媒体接入控制MAC层配置和半静态SPS配置中的一种或多种。
在上述第一方面的无线链路失败恢复方法中，可以在所述UE没有保存的CHO配置或未被使能CHO恢复的情况下，所述UE回退到除物理层专用配置、MAC层配置和/或SPS配置之外的在所述源小区使用的配置。
在上述第一方面的无线链路失败恢复方法中，所述切换失败可以包括：所述UE执行CHO失败、以及所述UE执行非CHO失败。
在上述第一方面的无线链路失败恢复方法中，还可以包括：所述UE执行CHO恢复过程，在所述CHO恢复过程的小区选择过程中，在所选择的小区是CHO候选小区的情况下，所述UE应用所保存的CHO配置，执行向所述CHO候选小区的CHO，在所选择的小区不是CHO候选小区的情况下，所述UE发起无线资源控制RRC连接重建立过程。
在上述第一方面的无线链路失败恢复方法中，可以在发起所述CHO恢复过程的初始化阶段，所述UE执行以下操作：在定时器T310正在运行的情况下，停止所述定时器T310；在主小区组MCG所关联的定时器T312正在运行的情况下，停止所述定时器T312。
根据本公开的第二方面，提供一种无线链路失败恢复方法，包括： 用户设备UE检测到发生切换失败；所述UE回退到除了物理层专用配置、媒体接入控制MAC层配置和/或半静态SPS配置之外的在源小区所使用的配置；以及所述UE执行基于条件切换CHO恢复过程，在所述CHO恢复过程的小区选择过程中，所选择的小区是CHO候选小区的情况下，所述UE回退到在所述源小区所使用的物理层专用配置、MAC层配置和/或SPS配置。
在上述第二方面的无线链路失败恢复方法中，可以在所述小区选择过程中，所选择的小区不是所述CHO候选小区的情况下，所述UE发起无线资源控制RRC连接重建立过程。
在上述第二方面的无线链路失败恢复方法中，可以在所选择的小区是所述CHO候选小区的情况下，所述UE基于回退后的配置并应用所保存的CHO配置，执行向所述CHO候选小区的CHO。
在上述第二方面的无线链路失败恢复方法中，可以在发起所述CHO恢复过程的初始化阶段，所述UE执行以下操作：在定时器T310正在运行的情况下，停止所述定时器T310；在主小区组MCG所关联的定时器T312正在运行的情况下，停止所述定时器T312。
根据本公开的第三方面，提供一种用户设备，包括：处理器；以及存储器，存储有指令；其中，所述指令在由所述处理器运行时执行根据上下文所述的无线链路失败恢复方法。
附图说明
为了更完整地理解本公开及其优势，现在将参考结合附图的以下描述，其中：
图1是表示连接态的用户设备UE通过切换过程来变更服务小区的顺序图。
图2是表示条件切换的流程的示意图。
图3是表示实施例1的基于条件切换进行无线链路恢复的流程图。
图4是表示实施例2的基于条件切换进行无线链路恢复的流程图。
图5表示本公开所涉及的用户设备UE的框图。
在附图中，相同或相似的结构均以相同或相似的附图标记进行标识。
具体实施方式
根据结合附图对本公开示例性实施例的以下详细描述，本公开的其它方面、优势和突出特征对于本领域技术人员将变得显而易见。
在本公开中，术语“包括”和“含有”及其派生词意为包括而非限制；术语“或”是包含性的，意为和/或。
在本说明书中，下述用于描述本公开原理的各种实施例只是说明，不应该以任何方式解释为限制公开的范围。参照附图的下述描述用于帮助全面理解由权利要求及其等同物限定的本公开的示例性实施例。下述描述包括多种具体细节来帮助理解，但这些细节应认为仅仅是示例性的。因此，本领域普通技术人员应认识到，在不背离本公开的范围和精神的情况下，可以对本文中描述的实施例进行多种改变和修改。此外，为了清楚和简洁起见，省略了公知功能和结构的描述。此外，贯穿附图，相同参考数字用于相似功能和操作。
下文以长期演进系统(Long Term Evolution，LTE)/NR移动通信系统及其后续的演进版本作为示例应用环境，具体描述了根据本公开的多个实施方式。需要指出的是，本公开不限于以下实施方式，而是适用于更多其它的无线通信系统。若无特殊说明，在本公开中，小区和基站的概念可以互相替换；LTE系统也可是5G及其之后的LTE系统(如称为eLTE系统，或者可以连接到5G核心网的LTE系统)，同时LTE可以用演进的通用陆地无线接入(Evolved Universal Terrestrial Radio Access，E-UTRA)或演进的通用陆地无线接入网E-UTRAN来替换。在本公开中，切换指的是网络侧发起的主小区(Primary Cell，PCell)的变更，包含小区间的主小区变更也包含小区内的主小区变更，即UE的主小区从源小区变更为目标小区，其中源小区和目标小区可以是同一个小区也可以是不同的小区，在此过程中，用于接入层安全的秘钥或安全算法也可随之更新。源小区也称为源基站，也可以是源 光束(beam)、源传输点(Transmission point，TRP)，目标小区也可称为目标基站，也可以是目标光束、目标传输点。源小区指的是切换过程发起之前所连接的为UE服务的小区即UE从之接收包含切换命令的RRC消息的小区。目标小区指的是切换过程成功完成之后UE所连接的为UE服务的小区，或者说是切换命令中所包含的目标小区标识所指示的小区、UE收到执行切换时所接入的小区。本公开所述切换命令用于触发UE执行切换，在NR系统中是包含同步重配置(Reconfigurationwithsync)信息元素的RRC重配置消息，更进一步地，是包含用于主小区组(Master Cell Group，MCG)的同步重配置(Reconfigurationwithsync)信息元素的RRC重配置消息。此时，切换也可称为同步重配置。在LTE系统中是包含移动控制信息(MobilityControlInformation)信息元素的RRC连接重配置消息。其中，所述同步重配置信息元素或移动控制信息信息元素包含目标小区的配置信息，例如目标小区标识、目标小区频率、目标小区的公共配置如系统信息、UE接入到目标小区所使用的随机接入配置、UE在目标小区的安全参数配置、UE在目标小区的无线承载配置等。然而，本公开所述实施例也可以适用于对主辅小区(Primary Secondary Cell，PSCell)的切换或变更情况。所述PSCell指的是辅小区组(SCG，Secondary Cell Group)中辅小区组变更或添加的过程中UE执行随机接入过程或初始物理上行共享信道(Physical Uplink Shared Channel，PUSCH)传输的服务小区。一般，PCell和PSCell统称为特殊小区(Special Cell，SpCell)。为便于描述，本公开中RRC重配置消息和RRC连接重配置消息等同；同理，其响应消息RRC重配置完成消息和RRC连接重配置完成消息等同。RRC连接重建立请求消息和RRC重建立请求消息等同，RRC重建立消息和RRC连接重建立消息等同；同理，其响应消息RRC重建立完成消息和RRC连接重建立完成消息等同。切换命令和包含切换命令的RRC消息等同，指触发UE执行切换的RRC消息或RRC消息中的配置。切换配置指切换命令中的全部或部分配置。取消、释放、删除、清空和清除等可以替换。执行、使 用和应用可替换。配置和重配置可以替换。链路和连接可以替换。监测(monitor)和检测(detect)可替换。条件切换命令和条件切换配置可替换。
在本申请中，UE在收到包含切换命令的无线资源控制(Radio Resource Control，RRC)消息之后，在发起切换过程之前仍然可保持和源基站的通信包括数据传输，以进一步减小数据传输中断的时间。
下述先简要描述本公开实施例所涉及到的在先技术。
现有机制中的一般切换过程：
连接态的用户移动性主要通过切换过程来实现，所述切换即指的是处于RRC连接态的UE变更服务小区(主小区)的过程。图1是表示连接态的用户设备UE通过切换过程来变更服务小区的顺序图。如图1所示，切换过程一般包括如下阶段：
阶段1：测量阶段。基站向用户设备(User Equipment，UE)下发测量配置；UE基于该测量配置对服务小区或邻小区所对应的无线链路进行测量，当满足所配置的测量上报条件时，UE向基站发送测量报告。测量阶段不是必须的，在基站在没有有效测量报告的时候也可以盲切换UE。
阶段2：切换准备阶段。基站结合收到的测量报告以及其他因素如基站负载等决定是否为该UE触发切换。若确定对该UE触发切换，则源基站通过向目标基站发送切换请求消息来发起切换准备过程。目标基站根据切换请求消息中UE的上下文和目标基站的可用资源等因素决定是否接受对该UE的本次切换请求，如果接受，则向源基站回复切换确认消息，其中切换确认消息中包含一条基站间(inter-node)的RRC消息即切换命令。
阶段3：切换执行阶段。源基站将切换命令下发给UE，并开始将该UE的数据转发给目标基站。收到切换命令的UE立即应用该切换命令的配置执行切换，通过随机接入过程接入到目标基站，向目标基站发送确认消息。其中，随机接入过程不是必须的。
阶段4：切换完成阶段。目标基站确认UE成功接入后，向源基站发送切换完成消息。源基站据此可以释放其上所保存的UE上下文。
基于条件的切换：
在上述的一般切换过程中，一种导致切换失败而造成较长时间数据传输中断的原因是切换命令下发的不及时导致的切换命令接收失败。对于该问题，Release 16引入了条件切换(conditional handover，CHO)。图2是表示条件切换的流程的示意图。在条件切换中，设置相对保守的测量报告门限，使得基站提前获取测量结果，并根据测量结果和选定的目标基站提前执行切换准备，这样基站可以在真正的切换条件(相对于所述保守的测量报告门限)满足之前，提前将包含CHO候选小区和相对应的CHO执行条件的切换命令RRC消息下发给UE。所述RRC消息(LTE系统中是RRC连接重配置消息)中支持包含多于一个的CHO候选小区以及每一个CHO候选小区对应的CHO配置(即候选目标小区所配置RRC连接重配置消息所包含的配置)和CHO执行条件。UE收到条件切换命令后，并不会立即执行切换，而是保存所接收到的CHO配置(即目标小区所配置的RRC重配置消息中所包含的配置)，并根据切换命令消息中携带的CHO候选小区对应的CHO执行条件开始监测源小区的链路质量或目标小区的链路质量以评估CHO执行条件是否满足。只有当监测到所配置的一个或多个CHO执行条件满足时，UE才开始根据所保存的CHO配置执行切换，接入到目标小区。一般来说，若CHO配置中包含完全配置信息元素(fullconfig)(或称fullconfig信息元素设置为TURE)，则UE直接应用CHO配置来切换到目标小区，也就是说所述CHO配置与源小区配置无关。否则，UE基于源小区配置的基础上来应用目标小区的CHO配置，也就是说(UE所保存的)CHO配置是基于源小区配置的增量配置。在执行切换的过程中，UE会停止评估所配置的CHO执行条件。总言之，条件切换是指只有当所配置的一个或多个CHO执行条件满足时才执行的切换过程。CHO执行条件可以是一个测量事件，比如所述条件是测量事件A3(在持续一段时间内邻小区比服务小区信号质量好过一个 偏移量)。所述邻小区对应CHO候选目标小区。一个CHO候选小区可以对应一个或多于一个CHO执行条件。当对一个候选小区配置了多个CHO执行条件时，只有当所有CHO执行条件都满足时，UE才开始执行对应的切换。一般来说，目前3GPP标准规范36.331和38.331(参见5.5.4章节)定义的所有测量事件，如A1～A5，都可作为CHO执行条件包含在CHO切换命令中。
现有机制中的链路恢复机制：
首先简介无线链路失败(Radio Link Failure，RLF)和切换失败(HandOver Failure，HOF)。在发生下述情况的一种或多种时，UE会认为发生了MCG的RLF：
情况1：用于无线链路失败检测定时器T310超时。UE的RRC层当检测到主小区Pcell的物理层问题时即收到来自底层的连续N310个失步(out-of-sync)指示时，且此时用于RRC过程控制的定时器T300(用于检测RRC连接建立过程)、T301(用于检测RRC连接重建立过程)、T304(用于检测切换过程)或T311(用于检测RRC连接重建过程中的小区选择阶段)不在运行的情况下，启动T310。N310是由网络侧配置的常数，若网络侧没有配置所述常数则UE使用预定义的默认值。
情况2：MCG所关联的定时器T312超时。T312用于在触发了测量报告时的无线链路失败检测。UE的RRC层在触发了一个触发类型设置为事件触发的且配置了可使用T312的测量标识(measurement ID)的测量报告时若T310正在运行，启动对应的T312。更具体地，LTE系统中在下述几种条件之一满足时启动T312：条件一：对一个测量标识(measurement ID)，若触发类型设置为事件触发(event)，且对一个或多个适用小区的所有经过层3滤波的测量在timetoTrigger时间内已满足应用于该事件的进入情况(entry condition)，且在UE保存的测量报告列表(VarMeasReportList)中对该测量标识不包含任何一个测量上报项时，若UE支持T312且对该事件(event)的配置中包含了T312可用的配置(useT312信息元素)，若T310正在运行，若T312 不在运行，则启动T312。条件二：对一个测量标识(measurement ID)，若触发类型设置为事件触发(event)，且对一个或多个不包含在触发小区列表(cellsTriggeredList)中的适用小区的所有经过层3滤波的测量在timetoTrigger时间内已满足应用于该事件的进入情况(entry condition)，若UE支持T312且对该事件(event)的配置中包含了T312可用的配置(useT312信息元素)，若T310正在运行，若T312不在运行，则启动T312。T312的值采用网络侧对所述测量标识所关联的测量对象(measurement object)配置的T312的值。
情况3：收到来自媒体接入控制(Medium Access Control，MAC)层的随机接入失败指示且此时用于RRC过程控制的定时器T300、T301、T304或T311不在运行。所述MAC指MCG对应的MAC。
情况4：收到来自MCG对应的无线链路控制(Radio Link Control，RLC)层的指示，所述指示用于指示对一个信令无线承载(Signaling Radio Bearer，SRB)或数据无线承载(Data Radio Bearer，DRB)所述RLC重传达到了最大次数。
对于HOF，UE依据检测切换过程的定时器T304来判断HOF的发生。UE在开始执行一个切换时启动T304，并应用切换命令中对应的RRC配置，在切换成功完成时停止T304。若发生T304超时，则UE认为发生了HOF。在HOF后，UE回退到切换执行之前在源小区所使用的配置。所述配置包含了每一个无线承载所对应的状态变量和参数，但并不包括物理层专用配置(指PhysicalConfigDedicated信息元素中的配置)、MAC专用配置(指mac-Mainconfig信息元素中的配置)和半静态配置(指sps-config信息元素中的配置)。
其次，介绍一下现有机制中的链路恢复机制。UE在发生主小区组的无线链路失败(Radio Link Failure，RLF)或者切换过程失败(HandOver Failure，HOF)后，会发起RRC连接重建立过程来重建/恢复与网络侧的连接。在发起的RRC连接重建立过程中，UE先执行小区选择过程来选择一个重建小区，并向其发送RRC连接重建立请求消息。当UE收到响应消息为RRC连接重建消息时，UE根据RRC连 接重建消息中的配置来重建立RRC连接，并向基站反馈RRC连接重建完成消息，成功结束所述RRC连接重建立过程。重建小区指的是UE用于发送RRC连接重建立请求消息并接收对应的响应消息的用于在RRC连接态下重建立RRC连接的小区。在RRC重建立过程中定义了一个定时器T311。当UE发起RRC连接重建立过程时启动T311。当在小区选择过程中选择到了一个用于重建的合适小区时，停止T311；若T311超时，UE也无法选择到一个合适小区，此时一般认为UE处于不在覆盖区(out of coverage)，UE会离开RRC连接态，进入到RRC空闲态或RRC不活动态(RRC_Inactive)。
利用保存的条件切换配置的无线链路恢复：
在条件切换场景下，从UE接收到并保存一个CHO配置的时刻到所对应CHO条件满足并按照收到的CHO配置执行切换的这段时间内，UE依然保持和源基站的通信。3GPP RAN2工作组第106次和第107次会议上对RLF/HOF时执行CHO过程达成了一个结论：在发生RLF或HOF时，UE通过小区选择过程先选择一个小区来执行链路恢复，若所选择的小区是一个CHO候选小区(即所述小区对应有所保存的CHO配置)，则UE按照该小区对应的CHO配置执行到该小区的切换；若所选择的小区不是CHO候选小区，UE通过向所选择的小区发送RRC连接建立请求来尝试恢复和网络侧的连接即采用传统的RRC连接重建立过程。这种链路恢复机制的增强在本公开中称为基于CHO配置的链路失败恢复机制(简称为CHO链路恢复机制)。一般情况下，服务小区通过RRC信令中的使能指示来使能UE的CHO链路恢复功能。目前仅支持UE在发生RLF/HOF后仅能执行一次CHO恢复。也就是说CHO恢复过程中执行的CHO如果发生失败，则UE直接进入空闲状态；在另一种实现方式中，UE直接触发RRC重建立过程。
通过MCG失败信息过程的无线链路恢复
3GPP RAN2工作组还引入了一种快速MCG链路恢复机制。快速MCG链路恢复机制是相对于现有链路恢复机制(即通过RRC连接重建立过程来恢复链路连接)而言的，也称MCG失败信息过程。该过 程的目的用于通知主基站所述UE发生了一个MCG无线链路失败。对于一个配置了分离(split)SRB1或SRB3的UE，当UE的MCG检测到了RLF时，若UE的MCG和SCG都不是被挂起状态(not suspended)且被配置了快速MCG链路恢复功能，则UE发起MCG失败信息过程，通过SCG链路将MCG链路失败的信息包含在MCG失败信息RRC消息中报告给主基站。收到MCG链路失败信息报告的主基站可以向UE发送RRC连接重配置消息来触发UE切换到一个新的小区或者发送RRC释放消息来释放UE的连接。定时器T316用于检测MCG失败信息过程。UE在发送MCG失败信息RRC消息时启动T316；当MCG传输恢复或收到网络侧的响应(如RRC释放消息或用于指示UE切换的RRC重配置消息)或发起RRC重建立过程时，停止T316；若T316超时，UE认为MCG失败信息过程结束，并发起RRC重建立过程进行MCG链路恢复。快速MCG链路恢复机制可以应用于被配置了MR-DC(Multi-Radio access technology Dual Connectivity)的情况，比如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)等。
本公开主要就配置了CHO的UE在RLF/HOF时如何恢复和网络侧的连接问题提出解决方法。更具体地，对在HOF时如何应用所保存的CHO配置切换到目标小区；在一个正在进行的CHO链路恢复过程中如何避免再次发生无线链路失败；或在UE同时配置了CHO恢复机制和MCG失败信息机制的情况下如何协调两种链路恢复机制来恢复链路的问题，是本公开所关注和解决的问题。
下述是本公开中基于上述问题在UE上执行的若干实施例。
实施例1
该实施例在UE上执行，更进一步在UE的RRC层执行。UE在发生到小区A的切换失败HOF时，将其RRC配置回退到执行切换之 前在源小区的配置，但是所述配置并不包含物理层专用配置和MAC配置，也就是说当前UE所使用的物理层专用配置和MAC配置都是来自此次HOF所对应的切换目标小区A的配置。若该UE有保存的CHO配置，且被网络侧使能了CHO恢复功能，则UE可能发起到CHO候选小区B的CHO恢复过程来恢复链路，而UE在CHO恢复过程中应用CHO候选小区B对应的CHO配置时，若所述CHO配置是增量(delta)配置，则UE所应用的小区B的物理层专用配置和MAC层配置是基于当前的相关配置(即小区A)的配置，而所保存的小区B的CHO配置并不是以所述小区A的相关配置的增量配置。这会使得在CHO切换后网络侧和UE所应用的配置不一致，这种不匹配的配置可以导致进一步的配置/链路失败。本实施例基于该问题提供解决方法。在本实施例中，可以执行CHO恢复来恢复链路的UE在发生HOF时，通过将物理层专用配置或MAC层专用配置回退到在切换之前源小区的配置，使UE在执行后续CHO恢复的CHO切换时，基于切换前源小区的配置来应用所保存的CHO候选小区的增量配置，从而在该切换后和网络侧保持RRC配置的一致性。
作为一例，图3是表示实施例1的基于条件切换进行无线链路恢复的流程图，如图3所示，基于条件切换的无线链路失败恢复方法的一例包括如下步骤。
步骤1：UE检测到发生切换失败(T304超时)。所述切换失败是UE执行传统非CHO切换失败，也可是UE执行CHO失败。所述传统非CHO切换失败指的是UE收到包含切换命令的RRC重配置消息后立即应用所收到的配置执行到目标小区的切换，包含无随机接入切换(切换命令中配置了rach-skip)、断开前仍连接(Make-Before-Break，MBB)切换(切换命令中配置了makebeforebreak)，以及双激活协议栈(Dual Active Protocol Stack，DAPS)切换(指在收到用于切换的RRC消息后的切换过程中维持和源小区的连接直到成功接入到目标小区后才释放源小区，所述RRC消息中包含DAPS切换配置的指示/使能)。
步骤2：若UE有保存的CHO配置时、或者UE有保存的CHO配置且被使能了CHO恢复时，在步骤1中HOF发生时，UE回退到源小区所使用的配置。具体而言，在UE默认被使能了CHO恢复的情况下，若UE有保存的CHO配置，则HOF发生时UE回退到源小区所使用的配置。另外，在UE没有默认被使能了CHO恢复的情况下，若UE有保存的CHO配置且被使能了CHO恢复，则HOF发生时UE回退到源小区所使用的配置。再有，所述源小区所使用的配置包含物理层专用配置、MAC层配置和SPS配置中的一种或多种。所述被使能了CHO恢复指的是在UE在接收到的包含CHO配置的RRC消息中被配置了CHO恢复使能指示(如用attemptCHO信息元素来标识，)或所述CHO恢复使能指示被设置为“TURE”或“1”。所述CHO恢复使能指示用于允许UE在链路失败后若所选择的小区是CHO候选小区则可以通过执行CHO来恢复链路。具体释义为：若其存在所述RRC消息中，那么在链路失败后的第一个小区选择过程中，若所选择的小区是CHO候选小区，则UE执行到该小区的CHO。
该步骤所述操作的另一种描述方式为：当发生切换失败时，若UE有保存的CHO配置、或者UE有保存的CHO配置且被使能了CHO恢复，则UE回退到源小区所使用的配置；否则，若UE没有保存的CHO配置或未被使能CHO恢复，则回退到除物理层专用配置、MAC层配置和/或SPS配置之外的在源小区使用的配置。
步骤3：UE执行CHO恢复过程，包括：UE执行一个小区选择过程，若所选择的(suitable)小区是一个CHO候选小区，UE应用对该小区所保存的CHO配置，执行到该小区的CHO；否则，UE发起RRC连接重建立过程。UE基于步骤2中所述UE回退后的配置的基础上来应用所保存的CHO配置。步骤3是可选的。
显然地，该实施例在步骤1之前还包括：UE接收来自源小区的包含CHO配置和CHO执行条件的RRC重配置消息，保存所述CHO配置，并根据RRC消息中所包含的CHO执行条件开始监测所述CHO执行条件是否满足。步骤1中HOF之前还可包括UE执行一个到目标 基站的切换。所述UE有保存的CHO配置也可描述为UE被配置了CHO。所述源小区为源PCell。
实施例2
该实施例在UE上执行，更进一步在UE的RRC层执行。该实施例与实施例1所述场景一致，用于切换失败后执行的CHO恢复过程后和网络侧保持RRC配置的一致性。该实施例与实施例1不同在于，UE是在CHO恢复过程中将其物理层配置等回退到在切换失败发生前源小区所使用的相应配置，从而确保UE可以正确应用所选择的小区所对应的保存的CHO配置执行切换。
作为另一例，图4是表示实施例2的基于条件切换进行无线链路恢复的流程图，如图4所示，基于条件切换的无线链路失败恢复方法的另一例包括如下步骤。
步骤1：UE发生切换失败(T304超时)。所述切换失败是UE执行传统非CHO切换失败，也可是UE执行CHO失败。所述传统非CHO切换失败指的是UE收到包含切换命令的RRC重配置消息后立即应用所收到的配置执行到目标小区的切换，包含无随机接入切换、MBB切换，以及DAPS切换。
步骤2：在步骤1中HOF发生时，UE回退到除了物理层专用配置、MAC层配置和/或SPS配置之外的在源小区所使用的配置。
步骤3：UE执行CHO恢复过程，包括：UE执行一个小区选择过程，若所选择的(suitable)小区是一个CHO候选小区，则UE执行下述操作：回退到在源小区所使用的物理层专用配置、MAC层配置和/或SPS配置，并基于当前的配置应用对该小区所保存的CHO配置，执行到该小区的CHO；否则若所选择的小区不是一个CHO候选小区，UE发起RRC连接重建立过程。所述基于当前的配置应用对该小区所保存的CHO配置指的是基于步骤2和该步骤3中UE回退后的RRC配置的基础上来应用所保存的CHO配置。
优选地，UE在有保存的CHO配置且被使能了CHO恢复时才执行步骤3。所述被使能了CHO恢复见实施例1所述，此处不赘述。
显然地，该实施例在步骤1之前还包括：UE接收来自源小区的包含CHO配置和CHO执行条件的RRC重配置消息，保存所述CHO配置，并根据RRC消息中所包含的CHO执行条件开始监测所述CHO执行条件是否满足。步骤1中HOF之前还可包括UE执行一个到目标基站的切换。所述UE有保存的CHO配置也可描述为UE被配置了CHO。所述源小区为源PCell。
实施例3
该实施例在UE上执行，更进一步在UE的RRC层执行。该实施例与实施例1所述场景一致，用于切换失败后执行的CHO恢复过程后和网络侧保持RRC配置的一致性。该实施例与实施例1不同在于，UE是在CHO恢复过程中不是将其物理层配置等回退到在切换失败发生前源小区所使用的相应配置，而且使用对应的系统默认配置，从而确保UE可以正确应用所选择的小区所对应的保存的CHO配置执行切换。
步骤1：UE发生切换失败(T304超时)。所述切换失败是UE执行传统非CHO切换失败，也可是UE执行CHO失败。所述传统非CHO切换失败指的是UE收到包含切换命令的RRC重配置消息后立即应用所收到的配置执行到目标小区的切换，包含无随机接入切换、MBB切换，以及DAPS切换。
步骤2：在步骤1中HOF发生时，UE回退到除了物理层专用配置、MAC层配置和/或SPS配置之外的在源小区所使用的配置。
步骤3：UE执行CHO恢复过程，包括：UE执行一个小区选择过程，若所选择的(suitable)小区是一个CHO候选小区，则UE执行下述操作：应用系统默认的物理层专用配置、默认MAC层配置和/或默认SPS配置，并基于当前的配置应用对该小区所保存的CHO配置，执行到该小区的CHO；否则若所选择的小区不是一个CHO候选小区， UE发起RRC连接重建立过程。所述基于当前的配置应用对该小区所保存的CHO配置指的是基于步骤2中UE回退后的RRC配置和该步骤3中所应用的系统默认配置的基础上来应用所保存的CHO配置。
优选地，UE在有保存的CHO配置且被使能了CHO恢复时才执行步骤3。所述被使能了CHO恢复参照实施例1中所述，此处不赘述。
步骤4：UE在CHO恢复过程中执行到所选择小区的CHO时，向目标小区发送一个指示信息。所述指示信息用于指示此次CHO是由于链路失败(HOF)而发起的。更进一步地，所述指示信息用于指示此次CHO中UE应用了系统默认的物理层专用配置、MAC层配置或SPS配置。所述指示信息可以包含在接入目标基站的随机接入过程中的第一个PUSCH(使用随机接入响应中所分配的资源传输的消息3)中以MAC控制元素(MAC Control Element，MAC CE)的方式或RRC消息(切换响应消息(T304运行时所生成并发送给目标小区的RRC连接重配置完成))的方式发送，或者切换成功后的第一个PUSCH中以MAC CE的方式或RRC消息的方式发送。所述切换成功可以是随机接入过程成功完成，如RRC层收到来自MAC层的随机接入过程成功完成指示。
显然地，该实施例在步骤1之前还包括：UE接收来自源小区的包含CHO配置和CHO执行条件的RRC重配置消息，保存所述CHO配置，并根据RRC消息中所包含的CHO执行条件开始监测所述CHO执行条件是否满足。步骤1中HOF之前还可包括UE执行一个到目标基站的切换。所述UE有保存的CHO配置也可描述为UE被配置了CHO。所述源小区为源PCell。
实施例4
该实施例在UE上执行，更进一步在UE的RRC层执行。该实施例与实施例3所述场景一致，用于解决切换失败后执行的CHO恢复过程后和网络侧保持RRC配置的一致性。该实施例与实施例3不同在于，为了保证UE和网络侧的配置一致性，UE在执行CHO时总是应 用系统默认的物理层专用配置、MAC配置或SPS配置，无论该CHO是否是由于链路失败触发的。通过该方式，让网络侧在对物理层专用配置、MAC层配置或SPS配置上保持和UE一致，从而确保UE可以正确应用所选择的小区所对应的保存的CHO配置执行切换。
步骤1：UE接收来自源小区的包含CHO配置和CHO执行条件的RRC重配置消息，保存所述CHO配置，并根据RRC消息中所包含的CHO执行条件开始监测所述CHO执行条件是否满足。
步骤2：UE执行CHO。在CHO过程中，UE执行下述操作：应用系统默认的物理层专用配置、MAC配置或SPS配置；应用目标小区所对应的所保存的CHO配置。所述CHO配置是基于当前UE配置的增强配置。优选地，所述CHO配置中不包括全配置指示。
优选地，UE在被使能了CHO恢复时才执行步骤2中的操作。所述被使能了CHO恢复参照实施例1中所述，此处不赘述。
所述UE有保存的CHO配置也可描述为UE被配置了CHO。所述源小区为源PCell。
该实施例中，UE所保存的由目标候选小区所配置的CHO配置(RRC重配置消息中包含的配置)中的物理层专用配置、MAC层配置或SPS配置总是基于系统默认的对应的配置的。也就是说，目标候选小区所配置的CHO配置中的上述配置总是基于系统默认的对应的配置的增量配置。
实施例5
该实施例在UE的RRC层执行。如背景技术部分所述，目前用于触发RLF的监测定时器有T310和T312。这两个定时器的触发条件不同，可以同时处于运行状态。当其中一个定时器超时后，会触发RLF，此时另一个定时器仍在运行，在CHO恢复过程中，若所述另一个正在运行的定时器此时超时，则会导致UE再次进入RLF状态，从而重新执行一个CHO恢复过程，这会延长链路中断的时间，影响服务的连续性。在该实施例中，若UE进入一个CHO恢复过程，则UE将正 在运行的RLF相关定时器停止，以避免上述情况的发生，缩短链路中断的时间。
步骤1：UE发生RLF，如在T310或T312超时，UE宣称RLF。
步骤2：UE发起CHO恢复过程。在发起CHO恢复过程的初始化阶段，UE执行下述操作：如有正在运行的T310，则停止T310；如有正在运行的MCG所关联的T312，则停止该T312。
优选地，所述发起CHO恢复过程的初始化阶段是指在发起小区选择过程之前。或者在发生RLF/HOF之后，UE就执行所述停止定时器的操作。优选地，UE在有保存的CHO配置且被使能了CHO恢复时才执行步骤2。所述被使能了CHO恢复见实施例1所述，此处不赘述。
步骤3：UE执行CHO恢复过程。CHO恢复过程如前所述，此处不赘述。
实施例6
该实施例给出了一种UE在配置了双连接的情况下发生MCG的RLF时，在同时使能了MCG失败信息功能和配置了CHO时，恢复链路的方法。考虑一种场景，在发生RLF或HOF时，UE先尝试执行MCG失败信息过程来恢复链路，而在接收到网络侧的响应消息之前，UE监测到CHO执行条件满足。该实施例对这种场景下的UE行为给出解决方法，使得UE可以确定是继续执行MCG失败信息过程等待网络侧的响应消息，还是执行CHO切换到所述执行条件得到满足的目标候选小区。
步骤1：UE发起MCG失败信息过程。
步骤2：UE停止正在执行的CHO执行条件的评估/监测。优选地，步骤2在MCG失败信息过程的初始化阶段执行。备选地，UE可以在RLF/HOF失败后发起MCG失败信息过程之前执行步骤2。
UE在有保存的CHO配置时执行步骤2。
实施例7
该实施例给出了一种UE在配置了双连接的情况下发生MCG的RLF时，在同时使能了MCG失败信息功能和配置了CHO时，恢复链路的方法。该实施例与实施例6场景相同。该实施例中，UE结束正在进行的MCG失败信息过程，执行所触发的CHO。
步骤1：UE发起MCG失败信息过程。在该过程中，UE启动T316，挂起MCG传输。
步骤2：UE触发一个CHO。UE在监测/评估到一个CHO候选小区的CHO执行条件满足时触发到该小区的CHO。
步骤3：UE停止T316。UE在发起CHO时即执行CHO的初始阶段停止T316。该步骤还包括，UE恢复(resume)MCG传输。
所述T316如背景部分所述，用于监测MCG失败信息过程。优选地，所述MCG传输，是所有SRB和DRB所对应的MCG传输。
实施例8：
在该实施例中，UE在执行CHO时，总是先结束一个MCG失败信息过程，在执行CHO。该实施例与实施例7场景相同，只是描述有不同。
步骤1：UE触发一个CHO。UE在监测/评估到一个CHO候选小区的CHO执行条件满足时触发到该小区的CHO。
步骤2：若有正在运行的T316，则UE停止T316。优选地，UE在发起CHO时即执行CHO的初始阶段停止T316。该步骤还包括，UE恢复MCG传输。
所述T316如背景部分所述，用于监测MCG失败信息过程。优选地，所述MCG传输，是所有SRB和DRB所对应的MCG传输。所述发起CHO时，指的是UE应用所保存的CHO配置。
实施例9
该实施例与实施例7场景相同，不同之处在于，在MCG失败信 息过程中触发CHO时，UE忽略所触发的CHO，即UE不执行所述触发的CHO。
步骤1：UE发起MCG失败信息过程。
步骤2：UE触发一个CHO。UE在监测/评估到一个CHO候选小区的CHO执行条件满足时触发到该小区的CHO。
步骤3：忽略所触发的CHO，不执行所述触发的CHO。
该实施例也可表述为，当触发一个CHO时，若T316不在运行(即没有正在进行的MCG失败信息过程)，则UE执行所述触发的CHO。或者，当触发一个CHO时，若T316正在运行(即有正在运行的MCG失败信息过程)，则UE不执行所述触发的CHO。
T316正在运行，也可表述为MCG传输被挂起。
上述实施例6～9也适用于PSCell的CHO场景，即UE有保存的对于PSCell的CHO配置。此时所述CHO发起/触发指的是PSCell对应的CHO发起/触发。
在本公开实施例中，对UE发起CHO或UE执行CHO恢复过程等UE执行的CHO相关操作，即使未显式说明，也应该理解为在所述UE执行操作之前还包括：UE接收来自源小区的包含CHO配置和CHO执行条件的RRC重配置消息，保存所述CHO配置，并根据RRC消息中所包含的CHO执行条件开始监测所述CHO执行条件是否满足。
实施例10
该实施例对本公开的用户设备进行说明。图5是表示本发明所涉及的用户设备UE的框图。如图5所示，该用户设备UE50包括处理器501和存储器502。处理器501例如可以包括微处理器、微控制器、嵌入式处理器等。存储器502例如可以包括易失性存储器(如随机存取存储器RAM)、硬盘驱动器(HDD)、非易失性存储器(如闪速存储器)、或其他存储器等。存储器502上存储有程序指令。该指令在由处理器501运行时，可以执行本发明中详细描述的上述无线链路恢复方法。
本公开中，一些不同实施例之间可以协同工作。
在本公开中，“基站”是指具有较大发射功率和较广覆盖面积的移动通信数据和控制交换中心，包括资源分配调度、数据接收发送等功能。“用户设备”是
指用户移动终端，例如包括移动电话、笔记本等可以与基站或者微基站进行无线通信的终端设备。
上文已经结合优选实施例对本公开的方法和涉及的设备进行了描述。本领域技术人员可以理解，上面示出的方法仅是示例性的。本公开的方法并不局限于上面示出的步骤和顺序。上面示出的基站和用户设备可以包括更多的模块，例如还可以包括可以开发的或者将来开发的可用于基站、MME、或UE的模块等等。上文中示出的各种标识仅是示例性的而不是限制性的，本公开并不局限于作为这些标识的示例的具体信元。本领域技术人员根据所示实施例的教导可以进行许多变化和修改。
运行在根据本公开的设备上的程序可以是通过控制中央处理单元(CPU)来使计算机实现本公开的实施例功能的程序。该程序或由该程序处理的信息可以临时存储在易失性存储器(如随机存取存储器RAM)、硬盘驱动器(HDD)、非易失性存储器(如闪速存储器)、或其他存储器系统中。
用于实现本公开各实施例功能的程序可以记录在计算机可读记录介质上。可以通过使计算机系统读取记录在所述记录介质上的程序并执行这些程序来实现相应的功能。此处的所谓“计算机系统”可以是嵌入在该设备中的计算机系统，可以包括操作系统或硬件(如外围设备)。“计算机可读记录介质”可以是半导体记录介质、光学记录介质、磁性记录介质、短时动态存储程序的记录介质、或计算机可读的任何其他记录介质。
用在上述实施例中的设备的各种特征或功能模块可以通过电路(例如，单片或多片集成电路)来实现或执行。设计用于执行本说明书所描述的功能的电路可以包括通用处理器、数字信号处理器(DSP)、专用集 成电路(ASIC)、现场可编程门阵列(FPGA)、或其他可编程逻辑器件、分立的门或晶体管逻辑、分立的硬件组件、或上述器件的任意组合。通用处理器可以是微处理器，也可以是任何现有的处理器、控制器、微控制器、或状态机。上述电路可以是数字电路，也可以是模拟电路。因半导体技术的进步而出现了替代现有集成电路的新的集成电路技术的情况下，本公开的一个或多个实施例也可以使用这些新的集成电路技术来实现。
此外，本公开并不局限于上述实施例。尽管已经描述了所述实施例的各种示例，但本公开并不局限于此。安装在室内或室外的固定或非移动电子设备可以用作终端设备或通信设备，如AV设备、厨房设备、清洁设备、空调、办公设备、自动贩售机、以及其他家用电器等。
如上，已经参考附图对本公开的实施例进行了详细描述。但是，具体的结构并不局限于上述实施例，本公开也包括不偏离本公开主旨的任何设计改动。另外，可以在权利要求的范围内对本公开进行多种改动，通过适当地组合不同实施例所公开的技术手段所得到的实施例也包含在本公开的技术范围内。此外，上述实施例中所描述的具有相同效果的组件可以相互替代。

Claims (2)

  1. 一种用户设备UE，包含被配置了实现下述操作的处理器：
    当检测到主小区组MCG的无线链路失败且主小区组MCG和辅小区组SCG传输都不处于挂起状态时，发起一个MCG失败信息过程以告知网络所述UE发生了MCG失败；
    若被配置了条件切换，则停止所述条件切换的执行条件评估；
    若被配置了条件主辅小区PSCell变更，则停止所述条件PSCell变更的执行条件评估；
    发送一个MCG失败信息消息。
  2. 一种在用户设备UE上执行的方法，包括：
    当检测到主小区组MCG的无线链路失败且主小区组MCG和辅小区组SCG传输都不处于挂起状态时，发起一个MCG失败信息过程以告知网络所述UE发生了MCG失败；
    若被配置了条件切换，则停止所述条件切换的执行条件评估；
    若被配置了条件主辅小区PSCell变更，则停止所述条件PSCell变更的执行条件评估；
    发送一个MCG失败信息消息。
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