CN112584551A

CN112584551A - Radio link failure recovery method and user equipment

Info

Publication number: CN112584551A
Application number: CN201910931891.5A
Authority: CN
Inventors: 常宁娟; 刘仁茂
Original assignee: Sharp Corp
Current assignee: Sharp Corp
Priority date: 2019-09-27
Filing date: 2019-09-27
Publication date: 2021-03-30
Also published as: WO2021057702A1

Abstract

The disclosure provides a radio link failure recovery method and user equipment. The radio link failure recovery method comprises the following steps: user Equipment (UE) initiates an RRC connection reestablishment process; in a cell selection procedure of the RRC connection re-establishment procedure, the UE identifies the selected conditional handover candidate cell in a radio link failure report, in case the selected cell is a conditional handover candidate cell of the UE.

Description

Radio link failure recovery method and user equipment

Technical Field

The present disclosure relates to the field of wireless communication technologies, and in particular, to a recovery method after a radio link failure and a user equipment.

Background

In 6.2018, a New research Project of 5G technical standards was approved at the third Generation Partnership Project (3rd Generation Partnership Project: 3GPP) RAN #80 Congress (see non-patent document: RP-181433: New WID on NR (New Radio) mobility enhancements). In addition, there is another new research project of Release 16 (see non-patent document: RP-190272: WID for Even funcher Mobility enhancement in E-UTRAN (Evolved-Universal Terrestrail Radio Access Network)). One of the research objectives of these two projects is to find a way to meet one of the mobility needs in the network: seamless handover, that is, handover interruption time of 0ms or close to 0ms can be satisfied during cell handover, and the robustness of handover is enhanced. Among the solutions under investigation to reduce HandOver interruption time and/or enhance HandOver robustness, there is a solution known as Conditional HandOver (CHO). In the CHO mechanism, the base station issues a handover command to the UE in advance, wherein the handover command includes condition configuration information. The UE saves the received conditional handover command and performs handover according to the previously received handover command when the configured condition is satisfied. Therefore, the success rate of receiving the switching command can be improved by issuing the switching command in advance, so that the success rate of switching is improved, and the time delay of service interruption caused by switching failure due to the failure of receiving the switching command is avoided.

The present disclosure proposes solutions to some of the problems of CHO implementation in NR systems and lte (long Term evolution) systems.

Disclosure of Invention

An object of an embodiment of the present disclosure is to propose a solution to the problem of implementing the CHO technique in the NR system and the LTE system. More specifically, the present disclosure proposes a solution to the problem of how to recover link connection using the saved CHO configuration when a radio link fails, such as how to set a radio link failure report in a scheme of recovering link connection using the saved CHO configuration. The embodiment of the disclosure provides a recovery method when a radio link in user equipment fails and corresponding user equipment.

According to a first aspect of the present disclosure, a radio link failure recovery method is provided, including: user Equipment (UE) initiates an RRC connection reestablishment process; in a cell selection procedure of the RRC connection re-establishment procedure, the UE identifies the selected conditional handover candidate cell in a radio link failure report, in case the selected cell is a conditional handover candidate cell of the UE.

In the foregoing method for recovering from a radio link failure according to the first aspect, the UE may set a link recovery cell identifier in a radio link failure Report variable VarRLF-Report as the selected conditional handover candidate cell identifier.

In the radio link failure recovery method according to the first aspect, when the selected cell is a candidate cell for conditional handover of the UE, the following operations may be further performed: the UE executes conditional switch to the selected cell, initiates a conditional switch process, applies the saved conditional switch configuration of the cell, and executes access to the selected cell.

In the radio link failure recovery method according to the first aspect, the RRC connection reestablishment procedure is continued when the selected cell is not a conditional handover candidate cell of the UE.

According to a second aspect of the present disclosure, there is provided a radio link failure recovery method, including: judging whether a Radio Link Failure (RLF) occurs in a radio link of User Equipment (UE); when the RLF occurs to the UE, if the UE is configured with conditional switching, the UE executes a cell selection process in a conditional switching link recovery process; in the case where the selected cell is a conditional handover candidate cell for the UE, the UE identifies the selected conditional handover candidate cell in a radio link failure report.

In the radio link failure recovery method according to the second aspect, the UE may set the link recovery cell id in the radio link failure Report variable VarRLF-Report as the selected conditional handover candidate cell id.

In the radio link failure recovery method according to the second aspect, when the selected cell is a candidate cell for conditional handover of the UE, the following operations may be further performed: operation 1: the UE executes the conditional switch to the selected cell, initiates the conditional switch process, applies the saved conditional switch configuration of the cell and executes the access to the selected cell; operation 2: and under the condition that available radio link failure or handover failure information is stored in a radio link failure report variable of the UE and the current Public Land Mobile Network (PLMN) of the UE is contained in a PLMN identification list stored in the radio link failure report variable, the UE contains indication information in a conditional handover completion message, wherein the indication information is used for indicating that the UE has the stored available radio link failure or handover failure related information.

In the radio link failure recovery method according to the second aspect, in a case where the selected cell is not a conditional handover candidate cell of the UE, an RRC connection re-establishment procedure is initiated.

According to a third aspect of the present disclosure, there is provided a user equipment comprising: a processor; and a memory storing instructions; wherein the instructions, when executed by the processor, perform the radio link failure recovery method as described above and below.

Drawings

For a more complete understanding of the present disclosure and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

fig. 1 is a sequence diagram showing a change of a serving cell by a connected user equipment UE through a handover procedure.

Fig. 2 is a schematic diagram showing a flow of condition switching.

Fig. 3 is a flowchart showing radio link recovery based on conditional handover when a radio link fails.

Fig. 4 is a block diagram showing a user equipment UE according to the present invention.

In the drawings, the same or similar structures are identified by the same or similar reference numerals.

Detailed Description

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

In the present disclosure, the terms "include" and "comprise," as well as derivatives thereof, mean inclusion without limitation; the term "or" is inclusive, meaning and/or.

In this specification, the various embodiments described below which are used to describe the principles of the present disclosure are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the present disclosure as defined by the claims and their equivalents. The following description includes various specific details to aid understanding, but such details are to be regarded as illustrative only. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the present disclosure. Moreover, descriptions of well-known functions and constructions are omitted for clarity and conciseness. Moreover, throughout the drawings, the same reference numerals are used for similar functions and operations.

Hereinafter, a Long Term Evolution (LTE)/NR mobile communication system and its subsequent Evolution are taken as an example application environment, and a plurality of embodiments according to the present disclosure are specifically described. However, it is to be noted that the present disclosure is not limited to the following embodiments, but is applicable to more other wireless communication systems. Unless otherwise specified, the concepts of cell and base station may be interchanged in this disclosure; the LTE system is also used to refer to the LTE system of 5G and beyond (e.g. referred to as the LTE system, or the LTE system that can be connected to the 5G core network), and LTE may be replaced by Evolved Universal Terrestrial Radio Access (E-UTRA) or Evolved Universal Terrestrial Radio Access network E-UTRAN. In this disclosure, handover refers to a change of a primary cell initiated by a network side, where the change of the primary cell including inter-cell also includes a change of a primary cell in a cell, that is, a primary cell of a UE is changed from a source cell to a target cell, where the source cell and the target cell may be the same cell or different cells, and in this process, a secret key or a security algorithm for access stratum security may also be updated accordingly. The source cell may also be referred to as a source base station, a source beam (beam), and a Transmission point (TRP), and the target cell may also be referred to as a target base station, a target beam, and a target Transmission point. The source cell refers to a cell serving the UE, which is connected before the handover procedure is initiated, i.e., a cell from which the UE receives an RRC message including a handover command. The target cell refers to a cell serving the UE to which the UE is connected after the handover procedure is successfully completed, or a cell indicated by a target cell identifier included in the handover command, or a cell accessed by the UE when the UE receives the handover command. The handover command is used to trigger the UE to perform handover, and in the NR system, the handover command is an RRC reconfiguration message including a synchronization reconfiguration (reconfiguration) information element, and further, an RRC reconfiguration message including a synchronization reconfiguration (reconfiguration) information element for a Master Cell Group (MCG). At this time, the handover may also be referred to as a synchronous reconfiguration of the MCG. In the LTE system, the RRC connection reconfiguration message includes a mobility control information (mobility control information) information element. The synchronization reconfiguration information element or the mobility control information element includes configuration information of the target cell, such as a target cell identifier, a target cell frequency, a common configuration of the target cell, such as system information, a random access configuration used by the UE to access the target cell, a security parameter configuration of the UE in the target cell, a radio bearer configuration of the UE in the target cell, and the like. For convenience of description, the RRC reconfiguration message and the RRC connection reconfiguration message are equivalent in this disclosure; similarly, the response message RRC reconfiguration complete message is equivalent to the RRC connection reconfiguration complete message. The RRC connection reestablishment request message is equal to the RRC reestablishment request message, and the RRC reestablishment message is equal to the RRC connection reestablishment message; similarly, the response message RRC reestablishment completion message is equivalent to the RRC connection reestablishment completion message. The handover command is equivalent to the RRC message containing the handover command, and refers to the RRC message or the configuration in the RRC message that triggers the UE to perform the handover. The handover configuration refers to all or part of the configuration in the handover command. Cancellation, release, deletion, cleanup, and the like may be substituted. Execution, use, and application are alternatives. Configuration and reconfiguration may be alternative. Links and connections may be replaced. Monitoring (monitor) and detection (detect) may be replaced. The conditional switch command and the conditional switch configuration are replaceable.

In the present application, after receiving a Radio Resource Control (RRC) message containing a handover command, the UE may still maintain communication with the source base station including data transmission before initiating the handover procedure, so as to further reduce the time for data transmission interruption.

The following presents a simplified summary of the prior art to which embodiments of the present disclosure relate.

General handover procedure in existing mechanisms:

the mobility of the connected user is mainly realized through a handover process, i.e. a process in which the UE in the RRC connected state changes the serving cell. Fig. 1 is a sequence diagram showing a change of a serving cell by a connected user equipment UE through a handover procedure. As shown in fig. 1, the handover procedure generally includes the following stages:

stage 1: and (5) a measuring stage. A base station issues measurement configuration to User Equipment (UE); and the UE measures the wireless link corresponding to the serving cell or the adjacent cell based on the measurement configuration, and sends a measurement report to the base station when the configured measurement reporting condition is met. The measurement phase is not necessary and the UE can also be handed over blindly when the base station has no valid measurement report.

And (2) stage: and a switching preparation phase. The base station determines whether to trigger a handover for the UE in conjunction with the received measurement reports and other factors such as base station loading. If the UE is determined to be triggered to be switched, the source base station initiates a switching preparation process by sending a switching request message to the target base station. The target base station determines whether to accept the switching request of the UE according to factors such as the context of the UE, the available resources of the target base station and the like in the switching request message, if so, the target base station replies a switching confirmation message to the source base station, wherein the switching confirmation message comprises an RRC message between base stations (inter-node), namely a switching command.

And (3) stage: and switching the execution phase. And the source base station issues the switching command to the UE and starts to forward the data of the UE to the target base station. The UE receiving the switching command immediately executes the switching by applying the configuration of the switching command, accesses to the target base station through the random access process and sends a confirmation message to the target base station. Wherein a random access procedure is not necessary.

And (4) stage: and a switching completion stage. And after the target base station confirms that the UE is successfully accessed, the target base station sends a switching completion message to the source base station. The source base station can release the UE context saved thereon accordingly.

As can be seen from the above, the handover procedure in the current system may cause interruption of data transmission, and in the LTE system of Release 14, optimization of the handover procedure, such as handover without a random access procedure, connection Before disconnection (mbeb), and the like, all aim to reduce data interruption time in the handover procedure.

Condition-based handover:

next, the switching based on the condition is briefly described. As mentioned above, in the requirement of Release 16 technology, it is required to satisfy the data interruption delay of "0 ms" as much as possible in the mobile handover process, and to improve the robustness of the handover to meet the mobility requirement of seamless handover in NR. In the current handover process, one reason for causing a handover failure and causing a long-time data transmission interruption is that the handover command fails to be received due to untimely issuing of the handover command. One possible approach to this problem is conditional based switching (shortly called conditional switching). Fig. 2 is a schematic diagram showing a flow of condition switching. In the conditional handover, 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 according to the measurement result and the selected target base station, so that the base station can issue a handover command containing a handover candidate cell and a handover execution condition to the UE in advance before a real handover condition (relative to the conservative measurement report threshold) is met, wherein the handover command carries a condition for the UE to perform handover. Different from the existing LTE handover mechanism, after receiving a conditional handover command, the UE does not immediately perform handover, but stores the received handover command configuration, and starts to monitor the link quality of the source cell or the link quality of the target cell according to the handover execution condition carried in the handover command message to evaluate whether the handover execution condition is satisfied. And only when the configured switching execution condition is monitored to be met, the UE starts to execute the stored switching command and accesses to the target cell. During the handover, the UE stops evaluating the configured handover performing conditions. In summary, conditional handover refers to a handover procedure that is performed only when one or more handover execution conditions configured are satisfied. For handover performing conditions, for example, the handover performing condition is a measurement event, such as measurement event a3 (neighbor cell signal quality is better than serving cell signal quality by an offset for a duration of time). The adjacent cell corresponds to a target cell for handover. Generally, all measurement events defined by current 3GPP standard specifications 36.331 and 38.331 (see section 5.5.4), such as a 1-a 5, can be included in the conditional handover command as handover execution conditions.

Link recovery mechanisms in existing mechanisms:

again, a link recovery mechanism of the existing mechanisms is introduced. In the existing mechanism, after RLF of the master cell group occurs or HandOver Failure (HOF) is performed by the UE (i.e., T304 times out), the UE initiates an RRC connection re-establishment procedure to reestablish/recover the connection with the network side. In the initiated RRC connection reestablishment procedure, the UE first performs a cell selection procedure to select a reestablishment cell, and sends an RRC connection reestablishment request message to the UE. And when the UE receives the response message as the RRC connection reestablishment message, the UE reestablishes the RRC connection according to the configuration in the RRC connection reestablishment message, feeds back the RRC connection reestablishment completion message to the base station, and successfully ends the RRC connection reestablishment process. The reestablished cell refers to a cell used by the UE to send an RRC connection reestablishment request message and receive a corresponding response message for reestablishing an RRC connection in an RRC connected state. A timer T311 is defined during RRC reestablishment. T311 is started when the UE initiates the RRC connection re-establishment procedure. When a suitable cell for re-establishment is selected in the cell selection process, T311 is stopped; if T311 is over, the UE cannot select a suitable cell, and it is generally considered that the UE is not in the coverage area (out of coverage), and the UE leaves the RRC connected state and enters the RRC idle state or the RRC Inactive state (RRC _ Inactive).

The link failure reporting mechanism in the existing mechanism is as follows:

in the current LTE system, the UE generates and stores a radio link failure Report (RLF Report) when a link failure or a handover failure occurs, for example, the UE variable for storing the RLF Report is VarRLF-Report. After resuming the connection with the network side (e.g., through the RRC reestablishment procedure or the RRC establishment procedure), the UE may inform the network side of the radio link failure report available thereon through an RRC message (rlf-InfoAvailable information element to indicate). For example, the UE may notify the network side that the UE has the saved available radio link failure report in an RRC connection reestablishment complete message (RRCConnectionReestablishmentComplete) in an RRC connection reestablishment process, an RRC connection reconfiguration complete message (RRCConnectionReconfigurationComplete) in an RRC connection reconfiguration process, an RRC connection setup complete message (RRCConnectionSetupComplete) in an RRC connection setup process, or an RRC connection recovery complete message (rrcconnectionresummecomplete) in an RRC connection recovery process. After receiving the indication, the network side may request the UE to report the radio link failure report stored by the UE through an RRC message (the request is indicated by the rlf-ReportReq information element in the UEInformationRequest message). The UE reports the saved radio link failure Report (indicated by the rlf-Report information element in the UEInformationResponse message) to the network side in a response RRC message. And the radio link failure report acquired by the network side is used for network optimization, such as network coverage and mobile robustness optimization. The radio link failure report may include: measurement results of an available source cell and neighbor cells at the time of link failure, location information, a primary cell identifier where the link failure occurs, a link failure type (RLF or HOF), a RLF reason, a time elapsed from connection failure to reporting of radio link failure, a time elapsed from last handover to connection failure, and the like. In addition, the RRC reestablishment cell identity in the radio link failure report may provide additional assistance information for the network side. For example, if the RRC reestablishment cell information in the radio link failure report does not exist, the network side may consider that the UE does not find any suitable cell (viable cell) in the radio link recovery process after the link failure, that is, the RRC connection reestablishment process, and then the UE may be in a coverage hole (coverage hole) when the radio link failure occurs; if the RRC reestablishment cell id in the radio link failure report is not the source cell where the UE is located when the failure occurs, the network side may consider that the UE failure is not due to premature handover. The RRC reestablishment cell id is obtained by including, in the RRC connection reestablishment process, the identifier of the RRC reestablishment cell for which the UE attempts RRC connection reestablishment after triggering the RRC connection reestablishment request message, in the radio link failure report.

Radio link recovery with saved conditional handover configuration:

after the condition switching is configured, the UE does not immediately perform the switching, but performs the switching according to the received or stored condition switching configuration after the corresponding condition is satisfied. And the UE still keeps communication with the source base station in the period from the moment when the UE receives the conditional switch configuration to the moment when the UE executes the switch according to the received conditional switch configuration. During this time, Radio Link Failure (RLF) between the UE and the source base station may occur. A conclusion is reached by the 3GPP RAN2 working group at conference 106 on the case where the handover execution condition for the above-described conditional handover is not met and RLF occurs: when RLF occurs, UE selects a cell to execute link recovery, if the selected cell is a candidate cell for conditional switch, the UE executes switch to the cell according to the corresponding conditional switch configuration of the cell; if the selected cell is not the candidate cell for conditional handover, the UE attempts to recover the connection with the network side by sending an RRC connection setup request to the selected cell. This enhancement of the link recovery mechanism is referred to in this disclosure as a conditional handover configuration based link failure recovery mechanism (for convenience of description, simply referred to as a conditional handover link recovery mechanism). The candidate cell for conditional handover refers to a (target) cell in the conditional handover configuration in the RRC message received by the UE for configuring conditional handover, i.e. a cell identified by a cell identifier in a synchronization reconfiguration information element (reconfiguration withsync) or a mobile control information element (mobility control info). The network side can configure one or more handover execution condition candidate cells for the UE at the same time.

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

As described above, the UE will include the reestablished cell id in the radio link failure report only after triggering the RRC connection reestablishment request message when attempting the RRC connection reestablishment procedure to the network side. However, in the conditional handover link recovery mechanism, the existing mechanism cannot realize this function, which is a concern of the present disclosure. The present disclosure proposes a solution to the problem of how to set a radio link failure report in a conditional handover link recovery mechanism upon radio link failure. By the method disclosed by the disclosure, the UE can include the cell identifier for attempting to recover the connection in the radio link failure report and report the cell identifier to the network side, so that more auxiliary information is provided for mobility performance optimization of the network side.

The following are several embodiments of the present disclosure performed on a UE based on the above issues. In the following embodiments, the UE configured with conditional handover includes the UE receiving an RRC message including a conditional handover command from a base station, saving a handover configuration in the handover command, and monitoring whether a handover execution condition is satisfied according to the handover execution condition. The handover configuration refers to the RRC configuration generated by the UE according to the configuration in the handover command. Optionally, the handover configuration refers to an RRC configuration generated by the UE according to the configuration in the handover command and/or the RRC configuration of the current UE. The handover execution condition, i.e. the UE performs the handover only if the condition is met, applies the handover configuration, the handover execution condition being included in the conditional handover command.

Example 1

The embodiment provides a method for setting a cell identifier in a radio link failure report in a conditional handover link recovery mechanism when a radio link fails. When the UE executes the link recovery by using the conditional switch link recovery mechanism, the network side can acquire the cell identification of the UE trying to connect the recovery from the radio link failure report reported by the UE, so that more accurate network problem positioning is carried out to optimize network configuration parameters such as a switch threshold parameter. Fig. 3 is a flowchart showing radio link recovery based on conditional handover when a radio link fails, and as shown in fig. 3, radio link recovery under the conditional handover link recovery mechanism includes the following steps.

Step 1: the UE initiates an RRC connection re-establishment procedure.

Step 2: 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, performing step 3A; otherwise, if the selected cell is not a candidate cell for conditional handover of the UE, step 3B is performed.

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

Step 3A: the UE performs the following operations:

operation 1: the UE identifies the selected conditional handover candidate cell in a radio link failure Report, e.g., the UE sets a cell identification information element in a saved radio link failure Report variable (VarRLF-Report) to the cell identification of the selected conditional handover candidate cell. The cell identifier may be a global cell identifier that uniquely identifies a cell globally in a wireless communication system, or may be a physical cell identifier or a frequency in which the cell is located. In the LTE system, the Global Cell identity is Evolved Cell Global Identity (ECGI) and is used to uniquely identify the Cell in the LTE system.

The information element for carrying the cell identifier may reuse a reestablishment cell identifier information element (reestablishment cell) in an existing mechanism, or may be a newly defined information element different from the reestablishment cell identifier information element, such as a conditional handover cell identifier (represented as a conditional handover information element), or a link recovery cell identifier (linkrecovercell or connectioncell, or recovery information element). The cell identity is used to instruct the UE to perform a recovery attempt (conditional handover) in a recovery procedure after a radio link failure. The name is not limited in this disclosure.

Operation 2: and the UE executes the conditional switch to the selected cell, initiates the conditional switch process, applies the stored conditional switch configuration of the cell and executes the access to the selected cell.

In one manner, the operation 1 is performed before the operation 2, that is, after the UE determines that the suitable cell selected in the cell selection process in the step 2 is the conditional handover candidate cell, the operation 1 is performed. In another way, the operation 1 is completed after the operation 2 or during the process of performing the operation 2, such as the UE performing the operation 1 in the initialization phase of initiating the conditional switch in the operation 2.

And step 3B: the RRC connection reestablishment procedure is continued, such as initiating transmission of an RRC connection reestablishment request message.

Optionally, as mentioned above, the UE determines whether the selected cell is a candidate cell for a conditional handover of the UE, when the reason that the UE is configured with the conditional handover and/or the reason that the RRC connection re-establishment procedure is initiated is that the RLF of the MCG is monitored or a handover failure (i.e. a timeout of a timer (e.g. T304) for detecting the handover procedure, which also includes a conditional handover failure) is detected). Optionally, the UE determines whether the selected cell is a candidate cell for conditional handover of the UE, when the UE is enabled with a conditional handover link recovery mechanism.

In this step, the UE is configured with conditional handover equivalent to the UE having a saved conditional handover configuration.

The selected cell being a candidate cell for conditional handover may also be described as being included in the saved conditional handover configuration, preferably in a reconfiguration information element (reconfiguration _ withsync) or in a mobility control information element (mobility _ control _ info) of the saved conditional handover configuration. The UE performs handover to the selected cell, that is, performs handover (or referred to as synchronization reconfiguration) to the cell according to the saved conditional handover configuration corresponding to the cell. In this operation, the UE may perform handover to the cell without waiting for the condition corresponding to the conditional handover candidate cell to be satisfied, and may also resume communication with the network side as soon as possible. The operation of performing conditional switching includes one or more of: starting a timer T304; executing target cell RRC configuration in the condition switching configuration corresponding to the target cell; executing the configuration in the synchronous reconfiguration information element corresponding to the target cell; downlink synchronization to a target cell; performing random access to a target cell; and generating an RRC reconfiguration complete message and submitting the message to a lower layer for transmission.

Example 2

The embodiment provides another method for setting the reestablished cell identity in the radio link failure report in the conditional handover link recovery mechanism when the radio link fails. When the UE executes the link recovery by using the conditional switch link recovery mechanism, the network side can acquire the cell identification of the UE trying to connect the recovery from the radio link failure report reported by the UE, so that more accurate network problem positioning is carried out to optimize network configuration parameters such as a switch threshold parameter. Different from embodiment 1, the conditional handover recovery mechanism is not executed in the RRC connection reestablishment process, but when the UE configured with conditional handover generates RLF, a cell selection process is executed first, and if the selected cell is a candidate cell for conditional handover, the UE executes handover to the cell according to the conditional handover configuration corresponding to the cell; if the selected cell is not a conditional handover candidate cell, the UE initiates an RRC connection re-establishment procedure.

Step 1: RLF occurs for the radio link of the UE. Rather, the MCG link undergoes RLF. Or a Handover Failure (HOF) occurs in the UE. The handover failure may be determined based on a timeout of a timer used to monitor the handover procedure, such as a T304 timeout. The switching comprises conditional switching. The handover failure also includes a conditional handover procedure failure.

Step 2: if the UE is configured with conditional handover, the UE performs a conditional handover link recovery procedure. Including performing a cell selection procedure. The cell selection procedure is performed in accordance with the cell selection procedure in standard protocol specification 38.304 or 36.304. The execution condition of step 2 further includes that the UE is enabled with a conditional handover link recovery mechanism.

The UE is configured with the conditional switch is equal to the UE has the stored conditional switch configuration.

And step 3: the cell selection procedure of step 2 selects a suitable cell. When a suitable cell is selected, if the selected cell is a candidate cell for conditional handover of the UE, performing step 4A; otherwise, if the selected cell is not a candidate cell for conditional handover of the UE, step 4B is performed.

Step 4A: the UE performs the following operations:

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

The information element for carrying the cell identifier may reuse a reestablishment cell identifier information element (reestablishment cell) in an existing mechanism, or may be a newly defined information element different from the reestablishment cell identifier information element, such as a conditional handover cell identifier (represented as a conditional handover information element), or a link recovery cell identifier (linkrecovercell or connectioncell, or recovery information element). The cell identity is used to instruct the UE to perform a recovery attempt (conditional handover) in a link recovery procedure after a radio link failure or handover failure. The name is not limited in this disclosure.

And step 4B: an RRC connection reestablishment procedure is initiated.

In the foregoing embodiments 1-2, before or during the execution of the conditional handover procedure by the UE, if a radio link failure or handover failure procedure occurs before (just before) the execution of the conditional handover procedure, that is, the execution of the conditional handover procedure is triggered for recovering the link connection when the link fails, the UE includes, in the stored radio link failure report, indication information for indicating a conditional handover target cell identifier, so as to notify the network side that the UE has executed the conditional handover in the cell corresponding to the cell identifier to recover the connection.

Example 3

This embodiment provides a method for reporting a radio link failure report to a network by a UE, which is performed when the UE configures a conditional handover.

Step 1: and the UE initiates conditional switching and executes access to the selected conditional switching candidate cell.

The UE initiates the condition switching when the condition switching execution condition monitored by the UE is satisfied. The access procedure performed by the UE to the selected conditional handover candidate cell is as described above, and is not described herein again.

Step 2: if the radio link failure report variable of the UE stores available radio link failure or handover failure information and the current Public Land Mobile Network (PLMN) of the UE is included in the PLMN identity list stored in the radio link failure report variable, the UE includes an indication information in the conditional handover complete message. The indication information is used to indicate that there is information related to a radio link failure or a handover failure available on the UE, and preferably, the current PLMN of the UE is a PLMN (Registered PLMN, RPLMN) currently Registered by the UE.

Example 4

This embodiment explains the user equipment of the present disclosure. Fig. 4 is a block diagram showing a user equipment UE according to the present invention. As shown in fig. 4, the user equipment UE40 includes a processor 401 and a memory 402. The processor 401 may include, for example, a microprocessor, a microcontroller, an embedded processor, or the like. The memory 402 may include, for example, volatile memory (e.g., random access memory RAM), a Hard Disk Drive (HDD), non-volatile memory (e.g., flash memory), or other memory, among others. The memory 402 has stored thereon program instructions. Which when executed by the processor 401 may perform the above described radio link recovery method detailed in the present invention.

In the present disclosure, some of the different embodiments may work in conjunction with each other.

In the present disclosure, a "base station" refers to a mobile communication data and control switching center having a large transmission power and a wide coverage area, and includes functions of resource allocation scheduling, data reception and transmission, and the like. "user equipment" refers to a user mobile terminal, and includes, for example, a mobile phone, a notebook, and other terminal equipment that can wirelessly communicate with a base station or a micro base station.

The method of the present disclosure and the related apparatus have been described above in connection with preferred embodiments. Those skilled in the art will appreciate that the methods illustrated above are exemplary only. The methods of the present disclosure are not limited to the steps or sequences shown above. The base station and the user equipment shown above may comprise further modules, for example, modules that may be developed or developed in the future, which may be available for the base station, MME, or UE, etc. The various identifiers shown above are merely exemplary and not limiting, and the present disclosure is not limited to the specific information elements that are examples of these identifiers. Many variations and modifications may occur to those skilled in the art in light of the teachings of the illustrated embodiments.

The program running on the apparatus according to the present disclosure may be a program that causes a computer to realize the functions of the embodiments of the present disclosure by controlling a Central Processing Unit (CPU). The program or information processed by the program may be temporarily stored in a volatile memory (such as a random access memory RAM), a Hard Disk Drive (HDD), a nonvolatile memory (such as a flash memory), or other memory system.

A program for implementing the functions of the embodiments of the present disclosure may be recorded on a computer-readable recording medium. The corresponding functions can be realized by causing a computer system to read the programs recorded on the recording medium and execute the programs. The term "computer system" as used herein may be a computer system embedded in the device and may include an operating system or hardware (e.g., peripheral devices). The "computer-readable recording medium" may be a semiconductor recording medium, an optical recording medium, a magnetic recording medium, a recording medium that stores a program for short-term dynamics, or any other recording medium that is readable by a computer.

Various features or functional blocks of the devices used in the above-described embodiments may be implemented or performed by circuitry (e.g., a single or multiple chip integrated circuits). Circuitry designed to perform the functions described herein may include a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. The circuit may be a digital circuit or an analog circuit. Where new integrated circuit technology has emerged as a replacement for existing integrated circuits due to advances in semiconductor technology, one or more embodiments of the present disclosure may also be implemented using such new integrated circuit technology.

Further, the present disclosure is not limited to the above-described embodiments. While various examples of the embodiments have been described, the present disclosure is not so limited. Fixed or non-mobile electronic devices installed indoors or outdoors may be used as terminal devices or communication devices, such as AV devices, kitchen devices, cleaning devices, air conditioners, office devices, vending machines, and other home appliances.

As above, the embodiments of the present disclosure have been described in detail with reference to the accompanying drawings. However, the specific configuration is not limited to the above embodiment, and the present disclosure also includes any design modification without departing from the gist of the present disclosure. In addition, various modifications can be made to the present disclosure within the scope of the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments are also included in the technical scope of the present disclosure. Further, components having the same effects described in the above embodiments may be substituted for each other.

Claims

1. A radio link failure recovery method, comprising:

user Equipment (UE) initiates an RRC connection reestablishment process;

in a cell selection procedure of the RRC connection re-establishment procedure, the UE identifies the selected conditional handover candidate cell in a radio link failure report, in case the selected cell is a conditional handover candidate cell of the UE.

2. The radio link failure recovery method according to claim 1,

and the UE sets the link recovery cell identifier in a radio link failure Report variable VarRLF-Report as the selected conditional switch candidate cell identifier.

3. The radio link failure recovery method according to claim 1 or 2,

in the case where the selected cell is a conditional handover candidate cell for the UE, further performing the following: the UE executes conditional switch to the selected cell, initiates a conditional switch process, applies the saved conditional switch configuration of the cell, and executes access to the selected cell.

4. The radio link failure recovery method according to claim 1 or 2,

continuing the RRC connection reestablishment procedure in the event that the selected cell is not a conditional handover candidate cell for the UE.

5. A user equipment, UE, comprising:

a processor; and

a memory storing instructions;

wherein the instructions, when executed by the processor, perform the radio link failure recovery method of any of claims 1 to 4.

6. A radio link failure recovery method, comprising:

judging whether a Radio Link Failure (RLF) occurs in a radio link of User Equipment (UE);

when the RLF occurs to the UE, if the UE is configured with conditional switching, the UE executes a cell selection process in a conditional switching link recovery process;

in the case where the selected cell is a conditional handover candidate cell for the UE, the UE identifies the selected conditional handover candidate cell in a radio link failure report.

7. The radio link failure recovery method according to claim 6,

8. The radio link failure recovery method according to claim 6 or 7,

in the case where the selected cell is a conditional handover candidate cell for the UE, further performing the following:

operation 1: the UE executes the conditional switch to the selected cell, initiates the conditional switch process, applies the saved conditional switch configuration of the cell and executes the access to the selected cell;

operation 2: and under the condition that available radio link failure or handover failure information is stored in a radio link failure report variable of the UE and the current Public Land Mobile Network (PLMN) of the UE is contained in a PLMN identification list stored in the radio link failure report variable, the UE contains indication information in a conditional handover completion message, wherein the indication information is used for indicating that the UE has the stored available radio link failure or handover failure related information.

9. The radio link failure recovery method according to claim 6 or 7,

initiating an RRC connection re-establishment procedure in the event that the selected cell is not a conditional handover candidate cell for the UE.

10. A user equipment, UE, comprising:

a processor; and

a memory storing instructions;

wherein the instructions, when executed by the processor, perform the radio link failure recovery method of any of claims 6 to 9.