WO2021013170A1 - 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
WO2021013170A1
WO2021013170A1 PCT/CN2020/103471 CN2020103471W WO2021013170A1 WO 2021013170 A1 WO2021013170 A1 WO 2021013170A1 CN 2020103471 W CN2020103471 W CN 2020103471W WO 2021013170 A1 WO2021013170 A1 WO 2021013170A1
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Prior art keywords
cell
handover
conditional
conditional handover
rrc connection
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PCT/CN2020/103471
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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 US17/628,161 priority Critical patent/US20220322173A1/en
Publication of WO2021013170A1 publication Critical patent/WO2021013170A1/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
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H04W36/0083—Determination of parameters used for hand-off, e.g. generation or modification of neighbour cell lists
    • H04W36/00837—Determination of triggering parameters for hand-off
    • 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
    • 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
    • H04W36/0058—Transmission of hand-off measurement information, e.g. measurement reports
    • 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
    • H04W76/00—Connection management
    • H04W76/20—Manipulation of established connections
    • H04W76/27—Transitions between radio resource control [RRC] states
    • 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
    • H04W36/0083—Determination of parameters used for hand-off, e.g. generation or modification of neighbour cell lists
    • H04W36/00835—Determination of neighbour cell lists
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/34—Reselection control
    • H04W36/36—Reselection control by user or terminal equipment
    • H04W36/362—Conditional handover

Definitions

  • the present disclosure relates to the field of wireless communication technologies. 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)mobilityenhancements.
  • 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 is enhanced. Robustness.
  • 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 conditions are met. In this way, the early issuance of the handover command can increase the success rate of handover command reception, thereby increasing 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 in implementing CHO in NR systems and LTE (Long Term Evolution) systems.
  • 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. Specifically, the present disclosure provides a recovery method when a wireless link fails in a user equipment and corresponding user equipment.
  • a method for recovering from a radio link failure including: user equipment UE initiates an RRC connection re-establishment process; in the cell selection process of the RRC connection re-establishment process, in the selected cell
  • the UE performs handover to the selected cell
  • the UE suspends except for signaling All radio bearers except radio bearer 0 (SRB0) continue the RRC connection re-establishment process.
  • SRB0 radio bearer 0
  • the UE in the initialization phase of the RRC connection re-establishment process, in the case that the UE does not save the conditional switching configuration, the UE suspends the signaling radio bearer All radio bearers except 0 (SRB0).
  • the reason for initiating the RRC connection re-establishment process is not that the radio link failure of the primary cell group MCG is monitored.
  • the UE suspends all radio bearers except Signaling Radio Bearer 0 (SRB0).
  • radio link failure recovery method of the first aspect when the UE is configured with conditional handover and/or the reason for initiating the RRC connection re-establishment process is to monitor the RLF of the MCG or when the handover fails, perform all Judging whether the cell selected by the UE is a candidate cell for conditional handover of the UE.
  • a method for recovering from a radio link failure includes: the UE initiates an RRC connection re-establishment procedure; during the initialization of the RRC connection re-establishment procedure, the UE suspends and cancels the message Let all radio bearers except radio bearer 0 (SRB0); in the cell selection process of the RRC connection re-establishment process, in the case that the selected cell is a conditional handover candidate cell of the UE, execute to the selected cell Cell handover; in the case that the selected cell is not a candidate cell for conditional handover of the UE, the UE continues the RRC connection re-establishment process.
  • SRB0 radio bearer 0
  • the UE may resume the suspended radio bearer before or after the handover to the selected cell or during the handover process.
  • the reason that the UE is configured with conditional handover and/or initiates the RRC connection re-establishment process is that the radio link failure RLF of the primary cell group MCG is detected Or when the handover fails, it is judged whether the cell selected by the UE is a candidate cell for conditional handover of the UE.
  • 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 a link failure recovery procedure in the first embodiment.
  • Fig. 3 is a block diagram showing a user equipment UE related to the present invention.
  • LTE Long Term Evolution
  • NR New Radio Access
  • E-UTRA Evolved Universal Terrestrial Radio Access
  • handover refers to the change of the primary cell initiated by the network side, including the primary cell change between cells and the primary cell change within the cell, that is, the primary cell of the UE is changed from the source cell to the target cell, where the source cell It can be the same cell as the target cell or a different cell.
  • the secret key or security algorithm used for access layer security is also updated.
  • the source cell may also be referred to as a source base station, and may also be a source beam (beam) or a source transmission point (TRP).
  • the target cell may also be referred to as a target base station, or 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 that sends the RRC message containing the handover command to the UE.
  • the target cell refers to the cell that the UE is connected 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.
  • 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, and furthermore, it contains a master cell group (MCG). ) RRC reconfiguration message of the reconfiguration (Reconfigurationwithsync) information element.
  • handover can also be referred to as MCG synchronous reconfiguration.
  • the LTE system it is an RRC connection reconfiguration message containing an information element of mobility control information (MobilityControlInformation).
  • 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 security parameter configuration in the target cell, UE radio bearer configuration in the target cell, etc.
  • 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
  • the RRC re-establishment message is equivalent to the RRC connection re-establishment message; similarly, 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. Monitoring (monitor) and detection (detect) can be replaced. Conditional switching commands and conditional switching configurations can be replaced.
  • the UE after the UE receives a radio resource control (Radio Resource Control, RRC) message containing a handover command, it still maintains 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
  • a handover process which refers to a process in which a UE in an RRC connected state changes a serving cell.
  • Fig. 1 is a sequence diagram showing that a user equipment UE in a connected state changes a serving cell through a handover process. See Fig. 1. The specific process is briefly described as follows:
  • Phase 1 Measurement phase.
  • the base station sends the measurement configuration to the User Equipment (UE); the UE measures the radio link corresponding to the serving cell or neighboring cell based on the measurement configuration, 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 base station load. If it is determined to trigger a handover for the UE, the source base station initiates the handover preparation process by sending a handover request message to the target base station.
  • the target base station decides whether to accept this handover request for the UE according to the UE context in the handover request message and the available resources of the target base station. If possible, 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 a 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 Handover completion phase. After the target base station confirms that the UE has successfully accessed, it sends a handover complete message to the source base station. The source base station can release the UE context stored on it accordingly.
  • the handover process in the current system will cause the interruption of data transmission.
  • the optimization of the handover process such as handover without random access process, will still connect before disconnection (Make Before Break, MBB). ) And so on are designed to reduce the data interruption time during the switching process.
  • condition-based switching As mentioned above, in the technical requirements of Release 16, it is required to meet the "0ms" data interruption delay as much as possible during the mobile handover process, and to improve the robustness of handover to meet the mobility requirements of seamless handover in NR.
  • condition-based switching condition switching for short.
  • a relatively conservative measurement report threshold is set so that the base station obtains the measurement results in advance, and performs handover preparations in advance according to the measurement results 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 is issued to the UE in advance, which carries the conditions for the UE to perform the handover.
  • the UE receives the conditional handover command, it does not immediately execute the handover, but saves the received handover command configuration, and starts monitoring the source cell according to the handover execution conditions carried in the handover command message. Link quality or link quality of the target cell.
  • the UE Only when it is monitored that the configured handover execution conditions are met, the UE starts to execute the saved handover command and accesses the target cell.
  • the switching mechanism the present disclosure refers to conditional switching, but does not limit its naming. It can also be referred to as the switching mechanism of the advance switching command, the advance switching, the early switching preparation, the switching including the switching execution conditions, and the like.
  • the UE initiates an RRC connection re-establishment process to reestablish/restore the connection with the network side.
  • 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 as the RRC connection reestablishment message, the UE re-establishes the RRC message according to the configuration in the RRC connection reestablishment message, and feeds back the RRC connection reestablishment complete message to the base station, and successfully ends the RRC connection reestablishment 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.
  • the UE After the UE is configured with the conditional switching, it will not immediately perform the switching, but only after the corresponding condition is satisfied will it perform the switching according to the received or saved conditional switching configuration. During the period from the moment the UE receives the conditional switching configuration to the execution of the switching according to the received conditional switching configuration, the UE still maintains communication with the source base station. During this period of time, a radio link failure (Radio Link Failure, RLF) between the UE and the source base station may occur. At the 106th meeting of the 3GPP RAN2 working group, the handover execution conditions for the above-mentioned conditional handover were not met and RLF occurred.
  • RLF Radio Link Failure
  • the conditional handover candidate cell refers to the (target) cell in the conditional handover configuration in the RRC message for configuring the conditional handover received by the UE, that is, the synchronization reconfiguration information element (ReconfigurationWithSync) or the mobility control information element (MobilityControlInfo).
  • the cell identified by the cell ID.
  • the network side can simultaneously configure one or more handover execution condition candidate cells for the UE.
  • the implementation method is as follows.
  • Implementation method 1 The UE configured with conditional switching initiates an RRC connection re-establishment process when RLF occurs.
  • the UE will perform a cell selection process. If the selected cell is a candidate cell for conditional handover, the UE performs handover to the cell according to the conditional handover configuration corresponding to the cell, and ends the RRC connection re-establishment process; if the selected cell is not a candidate cell for conditional handover, the UE continues During the RRC connection re-establishment process, an RRC connection re-establishment request message is sent to the selected reestablished cell.
  • Implementation method 2 The UE configured with conditional handover performs a cell selection process when RLF occurs. If the selected cell is a candidate cell for conditional handover, the UE performs handover to the cell according to the conditional handover configuration corresponding to the cell ; If the selected cell is not a candidate cell for conditional handover, the UE initiates an RRC connection re-establishment process.
  • the cell selection process can refer to 3GPP protocol specification 38.304 or 36.304. Regardless of method 1 or method 2, if it is used to determine whether the selected cell is a candidate cell for conditional handover in the cell selection process, if the cell selected in the cell selection process is a cell with a different radio access technology (ie Inter- RAT cell), the UE performs the operation of entering the RRC idle state, and the reason for the RRC release is RRC connection failure.
  • the operation of entering the RRC idle state can refer to section 5.3.11 of the protocol specification 38.331.
  • implementation method 1 the difference between implementation method 1 and implementation method 2 is: in implementation method 1, the cell selection process used to determine whether there are available conditional handover candidate cells for connection recovery is the cell selection process in the RRC connection re-establishment process. In Method 2, the cell selection process used to determine whether there are available conditional handover candidate cells for connection recovery is not the cell selection process in the RRC connection re-establishment process, but is a cell selection process independent of the RRC connection re-establishment process.
  • the present disclosure mainly proposes solutions to the problem of how to recover the UE configured with conditional handover during RLF and the connection problem on the network side. More specifically, when implementing method 1, because the UE always initiates the RRC connection re-establishment process first, and performs the initialization operations of the RRC connection re-establishment process, these operations are for the UE to perform the RRC connection re-establishment, but if The cell selected by the UE in the cell selection process is a candidate cell for conditional handover, and the initialization operation is unnecessary or inappropriate, so how to deal with the initialization operation is a concern of this disclosure. In addition, when implementing method 2, how to monitor the cell selection process and how to reduce unnecessary cell selection processes are the concerns of this disclosure.
  • conditional handover link recovery mechanism if the UE selects an available conditional handover candidate cell every time the RLF or handover fails, but the initiated conditional handover fails again, the UE will remain in this state and cycle. For example, if the UE configured with conditional handover candidate cells as cell 1, cell 2...cell 5 has RLF, the UE uses the conditional handover link recovery mechanism to select cell 1 to initiate the conditional handover, but the handover also fails, then the UE uses the conditional handover again The link recovery mechanism selects cell 2 to initiate a conditional handover, but the handover also fails. Similarly, the UE is in a handover failure-recurring conditional handover cycle. How to solve this problem is also the focus of this disclosure.
  • the UE when the UE is configured with conditional handover, the UE receives an RRC message containing a conditional handover command from the base station, saves the handover configuration in the handover command, and monitors the handover execution condition according to the handover execution condition Is it satisfied.
  • the handover configuration refers to the RRC configuration generated by the UE according to the configuration in the handover command.
  • the handover configuration refers to the RRC configuration generated by the UE according to the configuration in the handover command and the current RRC configuration of the UE.
  • the handover execution condition that is, the UE performs handover only when the condition is met, the handover configuration is applied, and the handover execution condition is included in a conditional handover command.
  • the handover execution condition is a measurement event, for example, the condition is a measurement event A3 (the signal quality of the neighboring cell is better than the serving cell by more than an offset for a period of time).
  • the neighboring cell corresponds to the target cell of handover.
  • all measurement events defined in the current 3GPP standard specifications 36.331 and 38.331 (see section 5.5.4), such as A1 to A5, can be included in the conditional switching command as the switching execution condition.
  • This embodiment proposes a solution to the problem of how to handle the initialization operation of the RRC connection re-establishment process in the foregoing implementation method 1.
  • the existing mechanism when the UE initiates the RRC connection re-establishment process, all radio bearers except the signaling radio bearer 0 (SRB0) will be suspended in the initialization phase.
  • SRB0 signaling radio bearer 0
  • implementation method 1 if the UE selects a candidate cell for conditional handover and restores the link connection by initiating handover, then how to deal with the radio bearer is the problem to be solved in this embodiment.
  • the radio bearer in the initialization operation will not be suspended in advance during the initialization phase of the RRC connection re-establishment process, thereby ensuring that the UE can be correct when selecting a conditional handover candidate cell for link failure recovery
  • the radio bearer is processed so as not to affect data transmission because the radio bearer is suspended.
  • Step 1 The UE initiates the RRC connection re-establishment process.
  • Step 2 In the initialization phase of the RRC connection re-establishment process, if the UE does not have a saved conditional switching configuration or (the UE has a saved conditional switching configuration) but the reason for initiating the RRC connection re-establishment process is not the RLF of the MCG is monitored or it is not If the handover fails (that is, the timer used to detect the handover process (such as T304) expires, and the conditional handover failure is also included here), the UE suspends all radio bearers except the signaling radio bearer 0 (SRB0).
  • SRB0 signaling radio bearer 0
  • Step 3 In the cell selection process in the RRC connection re-establishment process, when a suitable cell is selected, the following processing is performed. Specifically, as shown in Figure 2, Figure 2 is a schematic diagram showing the link failure recovery process in Embodiment 1. If the cell selected in the above cell selection process is a conditional handover candidate cell of the UE, execute Step 3A: UE performs handover to the selected cell; otherwise, if the selected cell is not a candidate cell for conditional handover of the UE, perform Step 3B: UE suspends except for signaling radio bearer 0 (SRB0) For all radio bearers in, continue the RRC connection re-establishment process, such as initiating the sending of an RRC connection re-establishment request message.
  • SRB0 signaling radio bearer 0
  • the UE determines whether the selected cell is a candidate cell for conditional handover of the UE.
  • the reason for the conditional handover and/or the initiation of the RRC connection re-establishment process is monitoring It is executed when the MCG RLF or handover fails (that is, the timer used to detect the handover process (such as T304) expires, and the conditional handover failure is also included here).
  • the UE determining whether the selected cell is a candidate cell for conditional handover of the UE is performed when the UE is enabled with the conditional handover link recovery mechanism.
  • the suspension of the radio bearer by the UE in step 3 may be performed before initiating the sending of the RRC connection re-establishment request message, or may be performed after initiating the RRC connection re-establishment request message.
  • the selected cell is a conditional handover candidate cell. It can also be described as that the selected cell is included in the saved conditional handover configuration.
  • the synchronization reconfiguration information element (ReconfigurationWithSync) is included in the saved conditional handover configuration. ) Or mobile control information information element.
  • the UE performs handover to the selected cell, that is, performs handover to the cell according to the saved conditional handover configuration corresponding to the cell (or called synchronous reconfiguration). In this operation, the UE may not need to wait until the condition corresponding to the conditional handover candidate cell is satisfied, and then it can perform handover to the cell and resume communication with the network side as soon as possible.
  • the operation of performing conditional handover includes one or more of the following: starting the timer T304; performing the target cell RRC configuration in the conditional handover configuration corresponding to the target cell; performing the configuration in the synchronization reconfiguration information element corresponding to the target cell ; Downlink synchronization to the target cell; perform random access to the target cell; generate an RRC reconfiguration complete message and submit it to the lower layer for transmission.
  • This embodiment proposes another solution to the problem of how to handle the initialization operation of the RRC connection re-establishment process in the foregoing implementation method 1.
  • the existing mechanism when the UE initiates the RRC connection re-establishment process, all radio bearers except the signaling radio bearer 0 (SRB0) will be suspended in the initialization phase.
  • SRB0 signaling radio bearer 0
  • implementation method 1 if the UE selects a candidate cell for conditional handover and restores the link connection by initiating handover, then how to deal with the radio bearer is the problem to be solved in this embodiment.
  • the suspended radio bearer in the initialization operation will perform the recovery operation when the UE selects a conditional handover candidate cell for link failure recovery, so that the radio bearer will not be affected by the handover. Suspend and affect data transmission.
  • Step 1 The UE initiates the RRC connection re-establishment process.
  • Step 2 During the initialization of the RRC connection re-establishment process, the UE suspends all radio bearers except the signaling radio bearer 0 (SRB0).
  • Step 3 In the cell selection process in the RRC connection re-establishment process, when a suitable cell is selected, if the selected cell is a conditional handover candidate cell of the UE, the UE resumes as described in step 2 For all suspended radio bearers, perform handover to the selected cell; otherwise, if the selected cell is not a conditional handover candidate for the UE, the UE continues the RRC connection re-establishment process, such as initiating the sending of an RRC connection re-establishment request message .
  • the UE determines whether the selected cell is a candidate cell for conditional handover of the UE.
  • the reason for the conditional handover and/or the initiation of the RRC connection re-establishment process is monitoring It is executed when the MCG RLF or handover fails (that is, the timer used to detect the handover process (such as T304) expires, and the conditional handover failure is also included here).
  • the UE determining whether the selected cell is a candidate cell for conditional handover of the UE is performed when the UE is enabled with the conditional handover link recovery mechanism.
  • the restoration of the radio bearer by the UE in step 3 may be performed before the handover to the selected cell is performed, or after the handover to the selected cell is initiated.
  • the selected cell is a conditional handover candidate cell. It can also be described as that the selected cell is included in the saved conditional handover configuration.
  • the synchronization reconfiguration information element (ReconfigurationWithSync) is included in the saved conditional handover configuration. ) Or mobile control information information element.
  • the UE performs handover to the selected cell, that is, performs handover to the cell according to the saved conditional handover configuration corresponding to the cell (or called synchronous reconfiguration). In this operation, the UE may not need to wait until the condition corresponding to the conditional handover candidate cell is satisfied, and then it can perform handover to the cell and resume communication with the network side as soon as possible.
  • the operation of performing conditional handover includes one or more of the following: starting the timer T304; performing the target cell RRC configuration in the conditional handover configuration corresponding to the target cell; performing the configuration in the synchronization reconfiguration information element corresponding to the target cell ; Downlink synchronization to the target cell; perform random access to the target cell; generate an RRC reconfiguration complete message and submit it to the lower layer for transmission.
  • This embodiment proposes yet another solution to the problem of how to handle the initialization operation of the RRC connection re-establishment process in the foregoing implementation method 1.
  • the existing mechanism when the UE initiates the RRC connection re-establishment process, all radio bearers except the signaling radio bearer 0 (SRB0) will be suspended in the initialization phase.
  • SRB0 signaling radio bearer 0
  • implementation method 1 if the UE selects a candidate cell for conditional handover and initiates handover to restore the link connection, then how to deal with the radio bearer is the problem solved by this embodiment.
  • the suspended radio bearer in the initialization operation will resume operation when the UE selects a candidate cell for conditional handover and performs the handover, so that the radio bearer will not be lost after the handover. Suspend and affect data transmission.
  • Step 1 The UE initiates a conditional switching process.
  • the initiating conditional handover process refers to applying the saved conditional handover configuration corresponding to the handover target cell to perform handover to the target cell.
  • Step 2 If the radio bearer is suspended, the UE resumes the suspended radio bearer.
  • the radio bearer does not include signaling radio bearer 0 (SRB0).
  • step 1 the UE initiates the conditional handover process because the UE selects a candidate cell for conditional handover through the cell selection process after the link fails. So before this step, there can be the following steps
  • Step 0-1 The UE initiates the RRC connection re-establishment process.
  • Step 0-2 During the initialization of the RRC connection re-establishment process, the UE suspends all radio bearers except the signaling radio bearer 0 (SRB0).
  • Step 0-3 In the cell selection process in the RRC connection re-establishment process, when a suitable cell is selected, if the selected cell is a conditional handover candidate for the UE, the UE performs handover to the selected cell; Otherwise, if the selected cell is not a conditional handover candidate cell of the UE, the UE continues the RRC connection re-establishment process, such as initiating the sending of an RRC connection re-establishment request message.
  • the UE determines whether the selected cell is a candidate cell for conditional handover of the UE.
  • the reason for the conditional handover and/or the initiation of the RRC connection re-establishment process is monitoring It is executed when the MCG RLF or handover fails (that is, the timer used to detect the handover process (such as T304) expires, and the conditional handover failure is also included here).
  • the UE determining whether the selected cell is a candidate cell for conditional handover of the UE is performed when the UE is enabled with the conditional handover link recovery mechanism.
  • the selected cell is a conditional handover candidate cell. It can also be described as that the selected cell is included in the saved conditional handover configuration.
  • the synchronization reconfiguration information element (ReconfigurationWithSync) is included in the saved conditional handover configuration. ) Or mobile control information information element.
  • the UE performs handover to the selected cell, that is, performs handover to the cell according to the saved conditional handover configuration corresponding to the cell (or called synchronous reconfiguration). In this operation, the UE may not need to wait until the condition corresponding to the conditional handover candidate cell is satisfied, and then it can perform handover to the cell and resume communication with the network side as soon as possible.
  • the operation of performing conditional handover includes one or more of the following: starting the timer T304; performing the target cell RRC configuration in the conditional handover configuration corresponding to the target cell; performing the configuration in the synchronization reconfiguration information element corresponding to the target cell ; Downlink synchronization to the target cell; perform random access to the target cell; generate an RRC reconfiguration complete message and submit it to the lower layer for transmission.
  • conditional handover is also equivalent to that the UE has a saved conditional handover configuration.
  • This embodiment proposes a cell selection process optimization method when using the conditional handover link recovery mechanism based on the foregoing implementation method 2.
  • the UE configured with conditional handover will first perform a cell selection process when RLF occurs. If the selected cell is a candidate cell for conditional handover, the UE will execute to the cell according to the conditional handover configuration corresponding to the cell. If the selected cell is not a candidate cell for conditional handover, the UE initiates the RRC connection re-establishment process. In the RRC connection re-establishment process, according to the existing mechanism, the UE also needs to perform a cell selection process to select a reestablished cell. It can be seen that in this process, the UE may perform the cell selection process twice. This embodiment aims to optimize the cell selection process in this case. With the method described in this embodiment, the UE can save unnecessary cell selection procedures, thereby saving energy overhead and shortening the delay of link recovery.
  • Step 1 RLF occurs on the radio link of the UE. More precisely, RLF occurs on the MCG link. Or the UE has a handover failure (Handover Failure, HOF).
  • the handover failure can be judged based on the timeout of the timer used to monitor the handover process, such as T304 timeout.
  • the switching includes conditional switching.
  • Step 2 If the UE is configured with conditional handover, the UE performs the conditional handover link recovery process. This includes performing a cell selection process. The cell selection process is performed in accordance with the cell selection process in the standard protocol specification 38.304 or 36.304. The execution condition of step 2 also includes that the UE is enabled with the conditional handover link recovery mechanism.
  • conditional handover configured for the UE is equivalent to that the UE has a saved conditional handover configuration.
  • Step 3 The cell selection process of step 2 selects a suitable cell. If the selected cell is a candidate cell for conditional handover, step 4A is executed. If the selected cell is not a candidate cell for conditional handover, step 4B is executed.
  • the selected cell is a conditional handover candidate cell. It can also be described as that the selected cell is included in the saved conditional handover configuration.
  • the synchronization reconfiguration information element (ReconfigurationWithSync) is included in the saved conditional handover configuration. ) Or mobile control information information element.
  • the selected suitable cell is an NR cell; in the LTE system, the selected suitable cell is an LTE/E-UTRAN cell.
  • Step 4A The UE performs handover to the selected cell. That is, the handover to the cell is executed according to the saved conditional handover configuration corresponding to the cell (or called synchronous reconfiguration). In this operation, the UE may not need to wait until the condition corresponding to the conditional handover candidate cell is satisfied, and then it can perform handover to the cell and resume communication with the network side as soon as possible.
  • the operation of performing conditional handover includes one or more of the following: starting the timer T304; performing the target cell RRC configuration in the conditional handover configuration corresponding to the target cell; performing the configuration in the synchronization reconfiguration information element corresponding to the target cell ; Downlink synchronization to the target cell; perform random access to the target cell; generate an RRC reconfiguration complete message and submit it to the lower layer for transmission.
  • Step 4B Initiate an RRC connection re-establishment process.
  • the UE does not need to perform the cell selection process to select its re-established cell, nor does it need to start T311, that is, the UE skips the cell selection process that performs the RRC connection re-establishment process.
  • the UE considers that the cell selected in the cell selection process in the conditional handover recovery mechanism in step 2 is the reestablished cell. That is, the UE uses the cell selected in the cell selection process in the conditional handover recovery mechanism in step 2 as the re-established cell.
  • step 4B can also be expressed as: initiating an RRC connection re-establishment process, in the initialization phase of the RRC connection re-establishment process, if the UE has a cell selection process before the RRC connection re-establishment process is initiated If the cell is selected, the UE uses the selected cell as a re-established cell and does not activate T311; otherwise, the UE activates T311 and executes the cell selection process to select a re-established cell. The UE has a cell selected in the cell selection process before the RRC connection re-establishment process is initiated.
  • the UE performs a cell selection process before the RRC connection re-establishment process is initiated, or in the RRC
  • the conditional handover link recovery process was performed before the connection re-establishment process was initiated, or there was a selected cell in the cell selection process in the performed conditional handover link recovery process, or it is expressed that the UE is configured for conditional handover and the RRC connection
  • the triggering cause of the re-establishment process is that the UE detects the RLF of the MCG or the handover fails.
  • This embodiment proposes a solution on how to monitor the cell selection process based on the implementation method 2.
  • the timer T311 is used to monitor the cell selection process for selecting the conditional handover target cell in the conditional handover link recovery mechanism.
  • the UE can determine in time whether it has selected a suitable cell or a conditional handover target cell, thereby avoiding the problem of link failure and interruption time caused by endless cell selection processes.
  • Step 1 RLF occurs on the radio link of the UE. More precisely, RLF occurs on the MCG link. Or the UE has a handover failure (Handover Failure, HOF).
  • the handover failure can be judged based on the timeout of the timer used to monitor the handover process, such as T304 timeout.
  • the switching includes conditional switching.
  • Step 2 If the UE is configured with conditional handover, the UE performs the conditional handover link recovery process, including the UE performing the following operations:
  • Operation 2 Perform cell selection process.
  • the cell selection process is performed in accordance with the cell selection process in the standard protocol specification 38.304 or 36.304.
  • Step 3 The cell selection process of step 2 selects a suitable cell, then stop T311. If the selected cell is a candidate cell for conditional handover, step 4A is executed. If the selected cell is not a candidate cell for conditional handover, step 4B is executed. If a suitable cell is not selected during the cell selection process, that is, T311 times out, the UE performs step 4C.
  • the selected cell is a conditional handover candidate cell. It can also be described as that the selected cell is included in the saved conditional handover configuration.
  • the synchronization reconfiguration information element (ReconfigurationWithSync) is included in the saved conditional handover configuration. ) Or mobile control information information element.
  • the selected suitable cell is an NR cell; in the LTE system, the selected suitable cell is an LTE/E-UTRAN cell.
  • Step 4A The UE performs handover to the selected cell.
  • Step 4B The UE initiates an RRC connection re-establishment process.
  • Step 4C Perform an operation to enter the RRC idle state, and the reason for the RRC release is RRC connection failure.
  • the operation of entering the RRC idle state can refer to section 5.3.11 of the protocol specification 38.331.
  • This embodiment proposes a solution to the problem that the aforementioned UE executes the conditional handover link recovery mechanism after link failure or handover fails, but encounters a failure when the conditional handover link resumes, and thus enters the conditional handover link recovery mechanism again.
  • the UE can jump out of the cycle.
  • the RRC connection re-establishment method is used to recover and Network side connection.
  • Step 1 MCG RLF occurs on the UE's radio link. Or the UE has a handover failure (Handover Failure, HOF).
  • the handover failure can be judged based on the timeout of the timer used to monitor the handover process, such as T304 timeout.
  • the switching includes conditional switching.
  • the UE performs the following steps:
  • Step 2 If the UE is configured with conditional handover, the UE compares the value of the counter COUNTER used to record the number of times of link recovery execution of the conditional handover with the configured threshold TH. If the value of the counter COUNTER is greater than or equal to TH, the UE executes step 4B. If the COUNTER value is less than or equal to or less than TH, the UE performs the cell selection process. The cell selection process is performed in accordance with the cell selection process in the standard protocol specification 38.304 or 36.304. The execution condition of step 2 also includes that the UE is enabled with the conditional handover link recovery mechanism.
  • conditional handover configured for the UE is equivalent to that the UE has a saved conditional handover configuration.
  • Step 3 The cell selection process of step 2 selects a suitable cell. If the selected cell is a candidate cell for conditional handover, step 4A is executed. If the selected cell is not a candidate cell for conditional handover, step 4B is executed.
  • the selected cell is a conditional handover candidate cell. It can also be described as that the selected cell is included in the saved conditional handover configuration.
  • the synchronization reconfiguration information element (ReconfigurationWithSync) is included in the saved conditional handover configuration. ) Or mobile control information information element.
  • Step 4A The UE performs handover to the selected cell. That is, the handover to the cell is executed according to the saved conditional handover configuration corresponding to the cell (or called synchronous reconfiguration). In this operation, the UE may not need to wait until the condition corresponding to the conditional handover candidate cell is satisfied, and then it can perform handover to the cell and resume communication with the network side as soon as possible.
  • the operation of performing conditional handover includes one or more of the following: starting the timer T304; performing the target cell RRC configuration in the conditional handover configuration corresponding to the target cell; performing the configuration in the synchronization reconfiguration information element corresponding to the target cell ; Downlink synchronization to the target cell; perform random access to the target cell; generate an RRC reconfiguration complete message and submit it to the lower layer for transmission.
  • This step also includes increasing the value of the counter COUNT by 1.
  • Step 4B Initiate an RRC connection re-establishment process.
  • the UE performs the following steps after step 1:
  • Step 2 The UE initiates the RRC connection re-establishment process.
  • Step 3 In the cell selection phase of the RRC connection re-establishment process, the UE selects a suitable cell. If the UE is configured with conditional handover, the UE compares the value of the counter COUNTER used to record the number of times of link recovery execution of the conditional handover with the configured threshold TH. If the value of the counter COUNTER is greater than or equal to TH, the UE executes step 4A. If the COUNTER value is less than or equal to or less than TH, the UE executes step 4B. The execution condition of step 3 also includes that the UE is enabled with the conditional handover link recovery mechanism.
  • Step 4A The UE continues the RRC connection re-establishment process, that is, initiates the sending of the RRC connection re-establishment request message to the selected reestablished cell. Optionally, it also includes resetting the value of COUNT to 0.
  • Step 4B Determine whether the selected cell is a candidate cell for conditional handover. If yes, go to step 5. If not, go to step 4A.
  • the selected cell is a conditional handover candidate cell. It can also be described as that the selected cell is included in the saved conditional handover configuration.
  • the synchronization reconfiguration information element (ReconfigurationWithSync) is included in the saved conditional handover configuration. ) Or mobile control information information element.
  • Step 5 The UE performs handover to the selected cell. That is, the handover to the cell is executed according to the saved conditional handover configuration corresponding to the cell (or called synchronous reconfiguration). In this operation, the UE may not need to wait until the condition corresponding to the conditional handover candidate cell is satisfied, and then it can perform handover to the cell and resume communication with the network side as soon as possible.
  • the operation of performing conditional handover includes one or more of the following: starting the timer T304; performing the target cell RRC configuration in the conditional handover configuration corresponding to the target cell; performing the configuration in the synchronization reconfiguration information element corresponding to the target cell ; Downlink synchronization to the target cell; perform random access to the target cell; generate an RRC reconfiguration complete message and submit it to the lower layer for transmission.
  • This step also includes increasing the value of the counter COUNT by 1.
  • this embodiment also includes when the UE performs handover successfully, or initiates the RRC connection re-establishment process, or successfully completes the RRC connection re-establishment process, or receives configuration information including the timer COUNT from the network side, such as When configuring the timer threshold, reset the value of COUNT to 0.
  • the successful execution of the handover may be that the MAC layer of the media intervention control layer indicates that the random access procedure for accessing the target cell has been successfully completed, or the RRC connection reconfiguration complete message used to respond to the handover command is successfully sent.
  • the successful completion of the RRC connection re-establishment process may be the successful reception of a response message of the RRC connection re-establishment request message, such as the RRC connection re-establishment message, or the successful transmission of the RRC connection re-establishment completion message.
  • step 1 it also includes that the UE receives configuration information including a timer COUNT, which includes the configuration of the timer threshold.
  • COUNT the value of COUNT can be pre-configured to 1. That is, the system only allows the UE to perform a conditional handover link recovery mechanism for a certain link failure or handover failure.
  • this embodiment can be implemented as:
  • Step 1 MCG RLF occurs on the UE's radio link. Or the UE has a handover failure (Handover Failure, HOF).
  • the handover failure can be judged based on the timeout of the timer used to monitor the handover process, such as T304 timeout.
  • the switching includes conditional switching.
  • Step 2 If the UE is configured with conditional handover and the UE has not performed the conditional handover recovery mechanism before step 1, the UE can perform the conditional handover recovery mechanism according to the implementation method 1 or the implementation method 2 and the foregoing embodiments.
  • conditional recovery mechanism that has not been executed may also be that the conditional recovery mechanism has not been executed within a period of time.
  • the period of time may be a pre-configured period of time, or a period of time configured by the network side through RRC signaling.
  • conditional recovery mechanism that has not been performed is that the UE did not perform the cell selection process just before step 1 or step 2, or that the UE did not select in the nearest cell selection process just before step 1 or step 2.
  • a conditional handover candidate cell is that the UE did not perform the cell selection process just before step 1 or step 2, or that the UE did not select in the nearest cell selection process just before step 1 or step 2.
  • FIG. 3 is a block diagram showing a user equipment UE related to the present invention.
  • the user equipment UE30 includes a processor 301 and a memory 302.
  • the processor 301 may include, for example, a microprocessor, a microcontroller, an embedded processor, and the like.
  • the memory 302 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 302 stores program instructions. When the instruction is run by the processor 301, 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 refers to 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 can 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 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 can 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.
  • the present disclosure is not limited to the above-mentioned embodiment. 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 conditioning, office equipment, vending machines, and other household appliances.

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Abstract

本发明提供一种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发起RRC连接重建立过程；在所述RRC连接重建立过程的小区选择过程中，在所选择的小区是所述UE的条件切换候选小区的情况下，所述UE执行到所选择小区的切换；在所选择的小区不是所述UE的条件切换候选小区的情况下，所述UE挂起除信令无线承载0(SRB0)之外的所有无线承载，继续所述RRC连接重建立过程。

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Release 16的新研究项目(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。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(Long Term Evolution)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。具体而言，本公开提供了在用户设备中无线链路失败时的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发起RRC连接重建立过程；在所述RRC连接重建立过程的小区选择过程中，在所选择的小区是所述UE的条件切换候选小区的情况下，所述UE执行到所选择小区的切换；在所选择的小区不是所述UE的条件切换候选小区的情况下，所述UE挂起除信令无线承载0(SRB0)之外的所有无线承载，继续所述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，可以在所述RRC连接重建立过程的初始化阶段，在所述UE没有保存条件切换配置的情况下，所述UE挂起除信令无线承载0(SRB0)之外的所有无线承载。
在上述第一方面的无线链路失败恢复方法中，可以在所述RRC连接重建立过程的初始化阶段，在发起所述RRC连接重建立过程的原因不是监测到主小区组MCG的无线链路失败RLF或者不是切换失败的情况下，所述UE挂起除信令无线承载0(SRB0)之外的所有无线承载。
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被配置了条件切换和/或发起所述RRC连接重建立过程的原因是监测到MCG的RLF或者切换失败时，执行所述UE所选择的小区是否为所述UE的条件切换候选小区的判断。
根据本公开的第二方面，提出了一种无线链路失败恢复方法，包括：所述UE发起RRC连接重建立过程；在所述RRC连接重建立过程的初始化时，所述UE挂起除信令无线承载0(SRB0)之外的所有 无线承载；在所述RRC连接重建立过程的小区选择过程中，在所选择的小区是所述UE的条件切换候选小区的情况下，执行到所选择小区的切换；在所选择的小区不是所述UE的条件切换候选小区的情况下，所述UE继续所述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，可以在执行到所选择小区的切换之前或者之后或者切换过程中，所述UE恢复被挂起的所述无线承载。
在上述第二方面的无线链路失败恢复方法中，可以在所述UE被配置了条件切换和/或发起所述RRC连接重建立过程的原因是监测到主小区组MCG的无线链路失败RLF或者切换失败时，执行所述UE所选择的小区是否为所述UE的条件切换候选小区的判断。
在上述第二方面的无线链路失败恢复方法中，可以在所述UE被使能了条件切换链路恢复机制时，执行所述UE所选择的小区是否为所述UE的条件切换候选小区的判断。
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是表示实施例1中的链路失败恢复过程的概略图。
图3是表示本发明所涉及的用户设备UE的框图。
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。然而，需要指出的是，本公开不限于以下实施方式，而是可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系统也用于指代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随之更新。源小区也可称为源基站，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服务的小区即向UE发送包含切换命令的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。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MCG的同步重配置。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。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。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，参见图1，具体流程简述如下：
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，如果可以，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。
从上可见，当前系统中的切换流程会引发数据传输的中断，Release 14版本的LTE系统中，对于切换流程的优化如无随机接入过程的切换，断开前仍连接(Make Before Break，MBB)等都旨在降低切换过程中的数据中断时间。
基于条件的切换：
其次简述基于条件的切换。如前所述在Release 16技术需求中，要求在移动切换过程中尽可能满足“0ms”的数据中断时延，并提高切换的鲁棒性以达到NR中的无缝切换的移动性需求。在当前的切换过程中，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，一种可行的方法是基于条件的切换(简称之条件切换)。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，提前将切换命令下发给UE，其中携带UE执行切换的条件。不同于LTE现有切换机制，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切换命令配置，并根据切换命令消息中携带的切换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。只有当监测到所配置的切换执行条件满足时，UE才开始执行所保存的切换命令，接入到目标小区。针对上述切换机制，本公开中称之条件切换，但并不限制其命名，也可以称提前切换命令的切换机制、预先切换、早切换准备、包含切换执行条件的切换等。
现有机制中的链路恢复机制：
再次，介绍一下现有机制中的链路恢复机制。在现有机制中，UE在发生主小区组的RLF时，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消息，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：
UE在配置了条件切换后，并不会立即执行切换，而是在所对应的条件满足之后才按照收到或保存的条件切换配置执行切换。在UE 接收到条件切换配置的时刻到按照收到的条件切换配置执行切换的这段时间内，UE依然保持和源基站的通信。在这段时间内，可能会发生UE和源基站之间的无线链路失败(Radio Link Failure，RLF)。3GPP RAN2工作组第106次会议上对上述条件切换的切换执行条件未满足且发生了RLF的情况达成了一个结论：在发生RLF时，若UE所保存的条件切换候选小区信号质量是好的，则可以执行到该小区的切换来恢复和网络侧的连接，而不是发起RRC连接重建立过程；否则UE选择其他非条件切换候选小区来发起RRC连接重建立过程来恢复和网络侧的连接。这种链路恢复机制的增强在本公开中称为基于条件切换配置的链路失败恢复机制(为描述方便，简称为条件切换链路恢复机制)。所述条件切换候选小区是指UE所接收到用于配置条件切换的RRC消息中的条件切换配置中的(目标)小区，即同步重配置信息元素(ReconfigurationWithSync)或移动控制信息元素(MobilityControlInfo)中的小区标识所标识的小区。网络侧可以同时为UE配置一个或多个切换执行条件候选小区。对于条件切换链路恢复机制，基于现有协议规范，其实现方法举例如下。
实现方法1：配置了条件切换的UE在发生RLF时，发起一个RRC连接重建立过程。根据现有机制，在RRC连接重建立过程的初始化阶段，UE将执行一个小区选择过程。若所选择的小区是一个条件切换候选小区，则UE按照该小区对应的条件切换配置执行到该小区的切换，结束RRC连接重建立过程；若所选择的小区不是条件切换候选小区，则UE继续RRC连接重建立过程，向所选择的重建小区发送RRC连接重建立请求消息。
实现方法2：配置了条件切换的UE在发生RLF时，先执行一个小区选择过程，若所选择的小区是一个条件切换候选小区，则UE按照该小区对应的条件切换配置执行到该小区的切换；若所选择的小区不是条件切换候选小区，则UE发起RRC连接重建立过程。
所述小区选择过程可参见3GPP协议规范38.304或36.304。无论是实现方法1还是实现方法2，若用于判断所选小区是否是条件切换 候选小区的小区选择过程中，若小区选择过程所选择的小区是一个不同无线接入技术的小区(即Inter-RAT小区)，则UE执行进入RRC空闲态的操作，且RRC释放理由为RRC连接失败。所述进入RRC空闲态的操作可参见协议规范38.331的5.3.11章节。
实现方法1和实现方法2的差别在于：在实现方法1中，用于确定是否有可用的条件切换候选小区来进行连接恢复的小区选择过程是RRC连接重建立过程中的小区选择过程，而实现方法2中，用于确定是否有可用的条件切换候选小区来进行连接恢复的小区选择过程不是RRC连接重建立过程中的小区选择过程，是独立于RRC连接重建立过程的一个小区选择过程。
本公开主要就配置了条件切换的UE在RLF时如何恢复和网络侧的连接问题提出解决方法。更具体地，在基于实现方法1时，因为UE总是会先发起RRC连接重建立过程，执行RRC连接重建立过程的初始化操作，这些操作是对于UE执行RRC连接重建立而言的，但是若UE在小区选择过程中所选小区是一个条件切换候选小区，则所述初始化操作是不必要或者不适当的，那么如何处理所述初始化操作是本公开所关注的问题。此外，在基于实现方法2时，如何监测小区选择过程以及如何减少不必要的小区选择过程是本公开所关注的问题。
此外，对于条件切换链路恢复机制，若UE在每次RLF或切换失败时都会选择到一个可用的条件切换候选小区，但发起的条件切换又发生失败，那么UE会处在这个状态循环下去。比如配置了条件切换候选小区为小区1、小区2……小区5的UE发生了RLF，UE使用条件切换链路恢复机制选择小区1发起条件切换，但该切换也失败，那么UE再次使用条件切换链路恢复机制选择小区2发起条件切换，但该切换也失败，类似如此，UE处于切换失败-重新发生条件切换的循环中。如何解决这个问题也是本公开所关注的。
下述是本公开中基于上述问题在UE上执行的若干实施例。在下述实施例中，所述UE被配置了条件切换就包含UE接收来自基站的 包含条件切换命令的RRC消息，保存所述切换命令中的切换配置，并根据切换执行条件监测所述切换执行条件是否满足。所述切换配置指UE根据所述切换命令中的配置而生成的RRC配置。可选地，所述切换配置指UE根据所述切换命令中的配置以及当前UE的RRC配置而生成的RRC配置。所述切换执行条件，即UE只有在所述条件满足时才执行切换，应用所述切换配置，所述切换执行条件包含在条件切换命令中。举例来说，切换执行条件是一个测量事件，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)。所述邻小区对应切换的目标小区。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，都可作为切换执行条件包含在条件切换命令中。
以下，对本发明所涉及的具体的示例以及实施例等进行详细说明。另外，如上所述，本公开中记载的示例以及实施例等是为了容易理解本发明而进行的示例性说明，并不是对本发明的限定。此外，对以下所记载的实施例进行适当的变更、组合、替换等而得到的技术方案也包含在本发明的范围中。
实施例1
该实施例对于前述实现方法1中如何处理所述RRC连接重建立过程初始化操作的问题提出了一种解决方法。现有机制中，当UE发起RRC连接重建立过程时，在初始化阶段会挂起(suspend)除信令无线承载0(SRB0)之外的所有无线承载。但是在实现方法1中，若UE选择到了一个条件切换候选小区并通过发起切换来恢复链路连接，那么如何处理所述无线承载是该实施例解决的问题。通过该实施例所述方法，所述初始化操作中的无线承载不会在RRC连接重建立过程初始化阶段被提前挂起，从而确保UE在选择了一个条件切换候选小区进行链路失败恢复时可以正确处理所述无线承载，从而不会因为无线承载被挂起而影响数据传输。
步骤1：UE发起RRC连接重建立过程。
步骤2：在RRC连接重建立过程的初始化阶段，若UE没有保存的条件切换配置或(UE有保存的条件切换配置)但所述发起RRC连接重建立过程的原因不是监测到了MCG的RLF或者不是切换失败(即用于检测切换过程的定时器(如T304)超时，此处也包括条件切换失败)，则UE挂起(suspend)除信令无线承载0(SRB0)之外的所有无线承载。
步骤3：在RRC连接重建立过程中的小区选择过程中，当选择了一个合适小区时，进行如下处理。具体而言，如图2所示，图2是表示表示实施例1中的链路失败恢复过程的概略图，若上述小区选择过程中所选择的小区是UE的一个条件切换候选小区，则执行步骤3A：UE执行到所选择小区的切换；否则，若所选择的小区不是UE的一个条件切换候选小区，则执行步骤3B：UE挂起(suspend)除信令无线承载0(SRB0)之外的所有无线承载，继续RRC连接重建立过程，如发起RRC连接重建立请求消息的发送。
可选地，如前所述，所述UE确定所选择的小区是否UE的一个条件切换候选小区的判断，在UE被配置了条件切换和/或所述发起RRC连接重建立过程的原因是监测到了MCG的RLF或者切换失败(即用于检测切换过程的定时器(如T304)超时，此处也包括条件切换失败)时执行。可选地，所述UE确定所选择的小区是否UE的一个条件切换候选小区的判断在UE被使能了条件切换链路恢复机制时执行。
所述步骤3中的UE挂起所述无线承载可以在发起RRC连接重建立请求消息的发送之前执行，也可以在发起RRC连接重建立请求消息之后执行。
该步骤中，所述UE被配置了条件切换等同于UE有保存的条件切换配置。
所述所选择的小区是一个条件切换候选小区也可以描述为所选择的小区包含在所保存的条件切换配置中，优选地，包含在所保存的条件切换配置中的同步重配置信息元素(ReconfigurationWithSync)中或 移动控制信息信息元素中。所述UE执行到所选小区的切换，即根据所保存的该小区所对应的条件切换配置执行到该小区的切换(或称同步重配置)。在该操作中，UE可以不需要等到所述条件切换候选小区对应的条件满足，就可以执行到该小区的切换也尽快恢复和网络侧的通信。所述执行条件切换的操作包含下述一个或多个：启动定时器T304；执行目标小区所对应的条件切换配置中的目标小区RRC配置；执行目标小区所对应的同步重配置信息元素中的配置；下行同步到目标小区；向目标小区执行随机接入；生成RRC重配置完成消息并递交给下层发送。
实施例2
该实施例对于前述实现方法1中如何处理所述RRC连接重建立过程初始化操作的问题提出了另一种解决方法。现有机制中，当UE发起RRC连接重建立过程时，在初始化阶段会挂起(suspend)除信令无线承载0(SRB0)之外的所有无线承载。但是在实现方法1中，若UE选择到了一个条件切换候选小区并通过发起切换来恢复链路连接，那么如何处理所述无线承载是该实施例解决的问题。通过该实施例所述方法，所述初始化操作中被挂起的无线承载会在UE选择了一个条件切换候选小区进行链路失败恢复时再执行恢复操作，从而不会因为在切换后无线承载被挂起而影响数据传输。
步骤1：UE发起RRC连接重建立过程。
步骤2：在RRC连接重建立过程的初始化时，UE挂起(suspend)除信令无线承载0(SRB0)之外的所有无线承载。
步骤3：在RRC连接重建立过程中的小区选择过程中，当选择了一个合适小区时，若所选择的小区是UE的一个条件切换候选小区，则UE恢复(resume)所述在步骤2中挂起的所有无线承载，执行到所选择小区的切换；否则，若所选择的小区不是UE的一个条件切换候选小区，则UE继续RRC连接重建立过程，如发起RRC连接重建立请求消息的发送。
可选地，如前所述，所述UE确定所选择的小区是否UE的一个条件切换候选小区的判断，在UE被配置了条件切换和/或所述发起RRC连接重建立过程的原因是监测到了MCG的RLF或者切换失败(即用于检测切换过程的定时器(如T304)超时，此处也包括条件切换失败)时执行。可选地，所述UE确定所选择的小区是否UE的一个条件切换候选小区的判断在UE被使能了条件切换链路恢复机制时执行。
所述步骤3中的UE恢复所述无线承载可以在执行到所选择小区的切换之前执行，也可以在发起执行到所选择小区的切换之后执行。
该步骤中，所述UE被配置了条件切换等同于UE有保存的条件切换配置。
所述所选择的小区是一个条件切换候选小区也可以描述为所选择的小区包含在所保存的条件切换配置中，优选地，包含在所保存的条件切换配置中的同步重配置信息元素(ReconfigurationWithSync)中或移动控制信息信息元素中。所述UE执行到所选小区的切换，即根据所保存的该小区所对应的条件切换配置执行到该小区的切换(或称同步重配置)。在该操作中，UE可以不需要等到所述条件切换候选小区对应的条件满足，就可以执行到该小区的切换也尽快恢复和网络侧的通信。所述执行条件切换的操作包含下述一个或多个：启动定时器T304；执行目标小区所对应的条件切换配置中的目标小区RRC配置；执行目标小区所对应的同步重配置信息元素中的配置；下行同步到目标小区；向目标小区执行随机接入；生成RRC重配置完成消息并递交给下层发送。
实施例3
该实施例对于前述实现方法1中如何处理所述RRC连接重建立过程初始化操作的问题提出了又一种解决方法。现有机制中，当UE发起RRC连接重建立过程时，在初始化阶段会挂起(suspend)除信令无线承载0(SRB0)之外的所有无线承载。但是在实现方法1中，若 UE选择到了一个条件切换候选小区并通过发起切换来恢复链路连接，那么如何处理所述无线承载是该实施例解决的问题。通过该实施例所述方法，所述初始化操作中被挂起的无线承载会在UE在选择一个条件切换候选小区并执行切换的过程中再执行恢复操作，从而不会因为在切换后无线承载被挂起而影响数据传输。
步骤1：UE发起条件切换过程。
所述发起条件切换过程指的是应用所保存的所述切换目标小区对应的条件切换配置来执行到所述目标小区的切换。
步骤2：若无线承载被挂起，则UE恢复所挂起的无线承载。优选地，所述无线承载不包含信令无线承载0(SRB0)。
在步骤1中，所述UE发起条件切换过程是因为UE在链路失败后通过小区选择过程选择到了一个条件切换候选小区而触发的。因此该步骤之前，还可以有下述步骤
步骤0-1：UE发起RRC连接重建立过程。
步骤0-2：在RRC连接重建立过程的初始化时，UE挂起(suspend)除信令无线承载0(SRB0)之外的所有无线承载。
步骤0-3：在RRC连接重建立过程中的小区选择过程中，当选择了一个合适小区时，若所选择的小区是UE的一个条件切换候选小区，则UE执行到所选择小区的切换；否则，若所选择的小区不是UE的一个条件切换候选小区，则UE继续RRC连接重建立过程，如发起RRC连接重建立请求消息的发送。
可选地，如前所述，所述UE确定所选择的小区是否UE的一个条件切换候选小区的判断，在UE被配置了条件切换和/或所述发起RRC连接重建立过程的原因是监测到了MCG的RLF或者切换失败(即用于检测切换过程的定时器(如T304)超时，此处也包括条件切换失败)时执行。可选地，所述UE确定所选择的小区是否UE的一个条件切换候选小区的判断在UE被使能了条件切换链路恢复机制时执行。
所述所选择的小区是一个条件切换候选小区也可以描述为所选择 的小区包含在所保存的条件切换配置中，优选地，包含在所保存的条件切换配置中的同步重配置信息元素(ReconfigurationWithSync)中或移动控制信息信息元素中。所述UE执行到所选小区的切换，即根据所保存的该小区所对应的条件切换配置执行到该小区的切换(或称同步重配置)。在该操作中，UE可以不需要等到所述条件切换候选小区对应的条件满足，就可以执行到该小区的切换也尽快恢复和网络侧的通信。所述执行条件切换的操作包含下述一个或多个：启动定时器T304；执行目标小区所对应的条件切换配置中的目标小区RRC配置；执行目标小区所对应的同步重配置信息元素中的配置；下行同步到目标小区；向目标小区执行随机接入；生成RRC重配置完成消息并递交给下层发送。
该步骤中，所述UE被配置了条件切换也等同于UE有保存的条件切换配置。
实施例4
该实施例提出了基于前述实现方法2的一种使用条件切换链路恢复机制时的小区选择过程优化方法。在实现方法2中，配置了条件切换的UE在发生RLF时，先执行一个小区选择过程，若所选择的小区是一个条件切换候选小区，则UE按照该小区对应的条件切换配置执行到该小区的切换；若所选择的小区不是条件切换候选小区，则UE发起RRC连接重建立过程。而在RRC连接重建立过程中，按照现有机制，UE也需要执行一个小区选择过程来选择一个重建小区。由此可见，在这个过程中，UE可能会执行两次小区选择过程。该实施例旨在优化这种情况下的小区选择过程。通过该实施例所述方法，UE可以省去执行不必要的小区选择过程，从而节省能量开销以及缩短链路恢复的时延。
步骤1：UE的无线链路发生RLF。更确切地，MCG链路发生RLF。或者UE发生切换失败(Handover Failure，HOF)。所述切换失败可基于用于监测切换过程的定时器超时来判断，如T304超时。所述切换 包含条件切换。
步骤2：如果UE被配置了条件切换，则UE执行条件切换链路恢复过程。其中包含执行一个小区选择过程。小区选择过程按照标准协议规范38.304或36.304中的小区选择过程执行。步骤2的执行条件还包括UE被使能了条件切换链路恢复机制。
所述UE被配置了条件切换等同于UE有保存的条件切换配置。
步骤3：步骤2的小区选择过程选择了一个合适小区。若所选择的小区是一个条件切换候选小区，则执行步骤4A。若所选择的小区不是一个条件切换候选小区，则执行步骤4B。
所述所选择的小区是一个条件切换候选小区也可以描述为所选择的小区包含在所保存的条件切换配置中，优选地，包含在所保存的条件切换配置中的同步重配置信息元素(ReconfigurationWithSync)中或移动控制信息信息元素中。
在NR系统中，所述选择的合适小区是NR小区；在LTE系统中，所述选择的合适小区是LTE/E-UTRAN小区。
步骤4A：UE执行到所选小区的切换。即根据所保存的该小区所对应的条件切换配置执行到该小区的切换(或称同步重配置)。在该操作中，UE可以不需要等到所述条件切换候选小区对应的条件满足，就可以执行到该小区的切换也尽快恢复和网络侧的通信。所述执行条件切换的操作包含下述一个或多个：启动定时器T304；执行目标小区所对应的条件切换配置中的目标小区RRC配置；执行目标小区所对应的同步重配置信息元素中的配置；下行同步到目标小区；向目标小区执行随机接入；生成RRC重配置完成消息并递交给下层发送。
步骤4B：发起一个RRC连接重建立过程。在所述RRC连接重建立过程的初始化阶段，UE无需执行小区选择过程来选择其重建小区，也无需启动T311，即UE跳过执行RRC连接重建立过程的小区选择过程。此时，UE认为之前在步骤2中条件切换恢复机制过程中的小区选择过程所选择的小区为重建小区。即UE将步骤2中条件切换恢复机制过程中的小区选择过程所选择的小区作为重建立小区。
结合前述步骤，步骤4B也可以表述为：发起一个RRC连接重建立过程，在所述RRC连接重建立过程的初始化阶段，若UE有一个在所述RRC连接重建立过程发起之前的小区选择过程中选择了的小区，则UE将该所选择的小区作为重建小区，且不启动T311；否则UE启动T311，并执行小区选择过程来选择一个重建小区。所述UE有一个在所述RRC连接重建立过程发起之前的小区选择过程中选择了的小区，还可以表述为UE在所述RRC连接重建立过程发起之前执行了一个小区选择过程，或者在RRC连接重建立过程发起之前执行了条件切换链路恢复过程，或者执行的条件切换链路恢复过程中的小区选择过程中有一个被选择小区，或者表述为UE被配置了条件切换且所述RRC连接重建立过程的触发原因为UE检测到了MCG的RLF或者发生了切换失败。
实施例5
该实施例就在基于所述实现方法2时如何监测小区选择过程提出解决方法。在该实施例中，使用定时器T311来监测用于条件切换链路恢复机制中选择条件切换目标小区的小区选择过程。通过该实施例所述方法，UE可以在及时确定是否选择到了合适小区或条件切换目标小区，从而避免无尽的小区选择过程而带来的链路失败中断时间过长的问题。
步骤1：UE的无线链路发生RLF。更确切地，MCG链路发生RLF。或者UE发生切换失败(Handover Failure，HOF)。所述切换失败可基于用于监测切换过程的定时器超时来判断，如T304超时。所述切换包含条件切换。
步骤2：如果UE被配置了条件切换，则UE执行条件切换链路恢复过程，包含UE执行下述操作：
操作1：启动定时器T311；
操作2：执行小区选择过程。小区选择过程按照标准协议规范38.304或36.304中的小区选择过程执行。
该步骤中，所述UE被配置了条件切换等同于UE有保存的条件切换配置。
步骤3：步骤2的小区选择过程选择了一个合适小区，则停止T311。若所选择的小区是一个条件切换候选小区，则执行步骤4A。若所选择的小区不是一个条件切换候选小区，则执行步骤4B。若小区选择过程没有选择到一个合适小区即T311超时，则UE执行步骤4C。
所述所选择的小区是一个条件切换候选小区也可以描述为所选择的小区包含在所保存的条件切换配置中，优选地，包含在所保存的条件切换配置中的同步重配置信息元素(ReconfigurationWithSync)中或移动控制信息信息元素中。
在NR系统中，所述选择的合适小区是NR小区；在LTE系统中，所述选择的合适小区是LTE/E-UTRAN小区。
步骤4A：UE执行到所选小区的切换。
步骤4B：UE发起一个RRC连接重建立过程。
步骤4C：执行进入RRC空闲态的操作，且RRC释放理由为RRC连接失败。所述进入RRC空闲态的操作可参见协议规范38.331的5.3.11章节。
实施例6
该实施例就前述UE在链路失败或切换失败后执行条件切换链路恢复机制，而在条件切换链路恢复时又遭遇失败，从而再次进入条件切换链路恢复机制的循环问题提出一种解决方法。在该实施例中，通过限定UE执行条件切换链路恢复的次数，从而使得UE可以跳出所述循环，在条件切换链路恢复机制不适合的情况下，通过RRC连接重建立的方式来恢复和网络侧的连接。
步骤1：UE的无线链路发生MCG RLF。或者UE发生切换失败(Handover Failure，HOF)。所述切换失败可基于用于监测切换过程的定时器超时来判断，如T304超时。所述切换包含条件切换。
基于前述实现方法2，则UE执行下述步骤：
步骤2：若UE配置了条件切换，则UE比较用于记录条件切换链路恢复执行次数的计数器COUNTER的值与所配置的门限值TH。若所述计数器COUNTER值大于或大于等于TH，则UE执行步骤4B。若COUNTER值小于等于或小于TH，则UE执行小区选择过程。小区选择过程按照标准协议规范38.304或36.304中的小区选择过程执行。步骤2的执行条件还包括UE被使能了条件切换链路恢复机制。
所述UE被配置了条件切换等同于UE有保存的条件切换配置。
步骤3：步骤2的小区选择过程选择了一个合适小区。若所选择的小区是一个条件切换候选小区，则执行步骤4A。若所选择的小区不是一个条件切换候选小区，则执行步骤4B。
所述所选择的小区是一个条件切换候选小区也可以描述为所选择的小区包含在所保存的条件切换配置中，优选地，包含在所保存的条件切换配置中的同步重配置信息元素(ReconfigurationWithSync)中或移动控制信息信息元素中。
步骤4A：UE执行到所选小区的切换。即根据所保存的该小区所对应的条件切换配置执行到该小区的切换(或称同步重配置)。在该操作中，UE可以不需要等到所述条件切换候选小区对应的条件满足，就可以执行到该小区的切换也尽快恢复和网络侧的通信。所述执行条件切换的操作包含下述一个或多个：启动定时器T304；执行目标小区所对应的条件切换配置中的目标小区RRC配置；执行目标小区所对应的同步重配置信息元素中的配置；下行同步到目标小区；向目标小区执行随机接入；生成RRC重配置完成消息并递交给下层发送。
该步骤中还包括将计数器COUNT值增加1。
步骤4B：发起一个RRC连接重建立过程。
基于前述实现方法1，UE在步骤1后执行下述步骤：
步骤2：UE发起RRC连接重建立过程。
步骤3：在RRC连接重建立过程中的小区选择阶段，UE选择到一个合适小区。若UE配置了条件切换，则UE比较用于记录条件切换链路恢复执行次数的计数器COUNTER的值与所配置的门限值TH。 若所述计数器COUNTER值大于或大于等于TH，则UE执行步骤4A。若COUNTER值小于等于或小于TH，则UE执行步骤4B。步骤3的执行条件还包括UE被使能了条件切换链路恢复机制。
步骤4A：UE继续RRC连接重建立过程，即发起向所选择的重建小区的RRC连接重建立请求消息的发送。可选地，还包括重置COUNT的值为0。
步骤4B：确定所选择的小区是否一个条件切换候选小区。若是，则执行步骤5。若否，则执行步骤4A。
所述所选择的小区是一个条件切换候选小区也可以描述为所选择的小区包含在所保存的条件切换配置中，优选地，包含在所保存的条件切换配置中的同步重配置信息元素(ReconfigurationWithSync)中或移动控制信息信息元素中。
步骤5：UE执行到所选小区的切换。即根据所保存的该小区所对应的条件切换配置执行到该小区的切换(或称同步重配置)。在该操作中，UE可以不需要等到所述条件切换候选小区对应的条件满足，就可以执行到该小区的切换也尽快恢复和网络侧的通信。所述执行条件切换的操作包含下述一个或多个：启动定时器T304；执行目标小区所对应的条件切换配置中的目标小区RRC配置；执行目标小区所对应的同步重配置信息元素中的配置；下行同步到目标小区；向目标小区执行随机接入；生成RRC重配置完成消息并递交给下层发送。
该步骤中还包括将计数器COUNT值增加1。
可选地，该实施例还包括当UE执行切换成功后，或发起RRC连接重建立流程后，或成功完成RRC连接重建立过程后，或收到来自网络侧的包含计时器COUNT的配置信息如计时器的门限值的配置时，重置COUNT的值为0。所述执行切换成功可以是媒体介入控制层MAC层指示已成功完成用于接入目标小区的随机接入过程，或者成功发送了用于响应切换命令的RRC连接重配置完成消息。所述成功完成RRC连接重建立过程可以是成功接收到了RRC连接重建立请求消息的响应消息如RRC连接重建立消息，或成功发送了RRC连接重建 立完成消息。
可选地，在步骤1之前，还包括UE接收包含计时器COUNT的配置信息，其中包含计时器的门限值的配置。
作为一种方式，COUNT的值可以预配置为1。也就是系统仅允许UE对某一次的链路失败或切换失败执行一次条件切换链路恢复机制。这种情况该实施例可以执行为：
步骤1：UE的无线链路发生MCG RLF。或者UE发生切换失败(Handover Failure，HOF)。所述切换失败可基于用于监测切换过程的定时器超时来判断，如T304超时。所述切换包含条件切换。
步骤2：若UE配置了条件切换，且UE在步骤1之前未执行过条件切换恢复机制，则UE可以按照实现方法1或实现方法2以及前述各实施例执行条件切换恢复机制。
所述未执行过条件恢复机制也可以是在一段时间内未执行过条件恢复机制。所述一段时间可以是预配置的时间长度，也可以是由网络侧通过RRC信令配置的一个时间长度。
优选地，所述未执行过条件恢复机制是就在步骤1或步骤2之前(just before)UE没有执行小区选择过程，或者就在步骤1或步骤2之前UE没有在最近的小区选择过程中选择一个条件切换候选小区。
实施例7
该实施例对本公开的用户设备进行说明。图3是表示本发明所涉及的用户设备UE的框图。如图3所示，该用户设备UE30包括处理器301和存储器302。处理器301例如可以包括微处理器、微控制器、嵌入式处理器等。存储器302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302上存储有程序指令。该指令在由处理器301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 (4)

  1. 一种UE设备，包括：
    处理器，被配置为：当发起一个无线资源控制RRC连接重建立过程，确定是否配置了条件切换配置，若UE未被配置条件切换配置，中断除信令无线承载SRB0之外的所有无线承载；
    以及被配置为：执行小区选择。
  2. 根据权利要求1所述的UE设备，其中，
    所述处理器被配置为：若RRC连接重建立流程是由监测到了主小区组MCG的无线链路失败RLF或MCG的同步重配置失败，且若UE被使能了条件切换链路恢复功能，且若所选择的小区是在所保存的条件切换配置中的同步重配置信息元素中所包含一个条件切换候选小区，则按照所选择的小区所关联的所保存的条件切换配置执行切换过程；否则，若UE被配置了条件切换配置，挂起除SRB0之外的所有无线承载。
  3. 一种无线链路失败恢复方法，包括：
    当发起一个无线资源控制RRC连接重建立过程，确定是否配置了条件切换配置，若UE未被配置条件切换配置，中断除信令无线承载SRB0之外的所有无线承载；和
    执行小区选择。
  4. 根据权利要求3所述的无线链路失败恢复方法，其中，
    若RRC连接重建立流程是由监测到了主小区组MCG的无线链路失败RLF或MCG的同步重配置失败，且若UE被使能了条件切换链路恢复功能，且若所选择的小区是在所保存的条件切换配置中的同步重配置信息元素中所包含一个条件切换候选小区，则按照所选择的小区所关联的所保存的条件切换配置执行切换过程；否则，若UE被配置了条件切换配置，挂起除SRB0之外的所有无线承载。
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