阅读说明：本技术 无线链路失败恢复方法及对应的用户设备 (Radio link failure recovery method and corresponding user equipment ) 是由 常宁娟 堀贵子 于 2020-05-13 设计创作，主要内容包括：本公开提供了一种切换时的链路失败恢复的方法以及相应的用户设备。在用户设备中执行的方法包括：在UE配置了双激活协议栈的切换过程成功后,若UE发生了主小区组的无线链路失败RLF,则在用于恢复连接的无线资源控制重建立过程中或者在源链路发生RLF时,UE执行从双激活协议栈回退到单激活协议栈的操作,释放源基站关联的协议栈和配置；在源基站的链路质量好时,UE释放目标基站关联的协议栈和配置,恢复和源基站的单连接状态,并将所述失败信息上报给基站。(The disclosure provides a method for recovering link failure during switching and corresponding user equipment. The method performed in the user equipment comprises: after the switching process of the UE configured with the double-activation protocol stack is successful, if the UE generates Radio Link Failure (RLF) of a main cell group, the UE executes the operation of returning from the double-activation protocol stack to the single-activation protocol stack in the radio resource control reestablishment process for recovering the connection or when the RLF occurs in a source link, and releases the protocol stack and the configuration associated with the source base station; and when the link quality of the source base station is good, the UE releases the protocol stack and the configuration associated with the target base station, recovers the single connection state with the source base station and reports the failure information to the base station.)

1. A radio link failure recovery method, comprising:

a User Equipment (UE) generates a Radio Link Failure (RLF) of a Master Cell Group (MCG);

the UE initiates a Radio Resource Control (RRC) connection reestablishment process to recover the connection with the network side;

in the RRC connection re-establishment process, if the UE is configured with a dual activation protocol stack DAPS bearer, the UE performs a change operation from the dual activation protocol stack to a single activation protocol stack, and releases a protocol stack and a configuration associated with a source base station.

2. The radio link failure recovery method of claim 1, wherein the UE performing a change operation from a dual active protocol stack to a single active protocol stack comprises one or more of:

operation 1: resetting the media access control MAC corresponding to the source base station and releasing the MAC configuration of the source base station;

operation 2: for each DAPS bearer, releasing a Radio Link Control (RLC) entity and a related logical channel of the source base station, and releasing a Protocol Data Convergence Protocol (PDCP) entity to release the DAPS;

operation 3: for each Signaling Radio Bearer (SRB), releasing a PDCP entity of the source base station, and releasing an RLC entity of the source base station and a logic channel related to the RLC entity;

and operation 4: releasing the physical channel configuration of the source base station;

operation 5: the security key used at the source base station is discarded.

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

when the UE configured with the DAPS bearer determines that the link between the UE and the source base station does not monitor the Radio Link Failure (RLF), the UE falls back to a single-active protocol stack state only maintaining connection with the source base station, and the method comprises the following operations:

operation 1: releasing the configuration of the target base station;

operation 2: resetting the MAC corresponding to the target base station and releasing the MAC configuration of the target base station;

operation 3: for each DAPS bearer, releasing the RLC entity of the target base station and the associated logical channel thereof, and reconfiguring PDCP release to release the DAPS;

and operation 4: for each SRB, releasing the PDCP entity of the target base station, releasing the RLC entity of the target base station and a logic channel associated with the RLC entity, and if the master key updating instruction is not received, configuring the PDCP entity of the source base station as the continuation of the state variable of the PDCP entity of the target base station;

operation 5: for each data radio bearer DRB which is not configured to be carried by the DAPS, if the master key updating indication is not received, configuring the PDCP entity of the source base station as the continuation of the state variable of the PDCP entity of the target base station;

operation 6: releasing the physical channel configuration of the target base station;

operation 7: discarding the security key used at the target base station;

operation 8: loss of any saved RRC messages; resuming the suspended SRB at the source base station;

operation 9: for each non-DAPS bearer, returning to the UE configuration used by the DRB of the source base station, wherein the UE configuration comprises PDCP (packet data convergence protocol), RLC (radio link control) state variables, security configuration and data stored in a sending and receiving buffer of PDCP and RLC entities;

operation 10: fallback to the measurement configuration used by the UE at the source base station.

Operation 11: a failure information procedure is initiated to report to the network side that RLF occurred at the target base station with DAPS configured. Preferably, in the process of the failure information, a failure reason included in an RRC message for reporting the failure information is set to be an MCG RLF configured with a DAPS.

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

the UE occurrence of MCG RLF occurs after the UE successfully completes a DAPS handover to a target base station.

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

and when the link between the UE configured with the DAPS bearer and the source base station monitors that RLF occurs, initiating an RRC connection reestablishment process.

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

the UE performs the change operation from the double-active protocol stack to the single-active protocol stack when receiving the RRC message containing the indication information for releasing the source base station from the network side.

7. The radio link failure recovery method according to claim 1 or 6,

the method comprises the steps that UE sends RRC information containing DAPS indication information to a network side, wherein the DAPS indication information is used for indicating that the UE is configured with a DAPS bearer; preferably, the RRC message is an RRC reestablishment request message or an RRC reestablishment request complete message.

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

the UE configured with a DAPS bearer is that one or more DRBs of the UE are configured with a DAPS configuration information element for indicating to perform a DAPS handover operation.

9. The radio link failure recovery method according to claim 5,

when the UE monitors that the link of the source base station has RLF, the UE performs one or more of the following operations:

operation 1: resetting the MAC corresponding to the source base station and releasing the MAC configuration of the source base station;

operation 2: for each DAPS bearer, releasing the RLC entity of the source base station and the associated logical channel thereof, and reconfiguring PDCP release to release the DAPS;

operation 3: for each SRB, releasing a PDCP entity of the source base station, and releasing an RLC entity of the source base station and a logic channel associated with the RLC entity;

and operation 4: releasing the physical channel configuration of the source base station;

operation 5: the security key used at the source base station is discarded.

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 1 to 9.

Technical Field

The present disclosure relates to the field of wireless communication technologies, and in particular, to a handover method and a corresponding user equipment.

Background

In 6.2018, a New research Project of 5G technical standard 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) and a New research Project of Long Term Evolution System (LTE) Release 16 (see non-patent document: RP-181544). One of the research objectives of these two projects is to find a solution for meeting one of the mobility requirements: seamless handover, i.e. handover interruption time of zero ms or close to zero ms can be met during handover to change the serving cell of the UE. Among the solutions under investigation to reduce the handover interruption time, there is a solution that is a Dual Active Protocol Stack (Dual Active Protocol Stack) mechanism. In the DAPS mechanism, after receiving a handover command, the UE does not cut off a link (data transmission) with the source base station in the handover process of accessing to the target base station, but can simultaneously maintain the connection and data transmission with the target base station and the source base station, thereby avoiding a delay caused by service interruption due to disconnection with the source base station before accessing to the target base station in the handover process.

The present disclosure proposes a solution to the problem of how to implement a DAPS mechanism in an LTE system or an NR system.

Disclosure of Invention

An object of embodiments of the present disclosure is to propose a solution to the problem of implementing the DAPS mechanism in an LTE/NR system. More specifically, the present disclosure provides a solution to the problem of how to fall back to the conventional single activation protocol stack by the UE in the case of Radio Link Failure (RLF) of the target cell after the DAPS handover is successfully performed and the target cell is accessed in the LTE/NR system. The embodiment of the disclosure provides a method for recovering radio link failure when a DAPS is configured and executed in user equipment, and corresponding user equipment.

According to a first aspect of the present disclosure, a method performed in a user equipment, UE, is presented, comprising: a User Equipment (UE) generates a Radio Link Failure (RLF) of a Master Cell Group (MCG), and the UE initiates a Radio Resource Control (RRC) connection reestablishment process to recover the connection with a network side; in the RRC connection re-establishment process, if the UE is configured with a dual activation protocol stack DAPS bearer, the UE performs a change operation from the dual activation protocol stack to a single activation protocol stack, and releases a protocol stack and a configuration associated with a source base station.

In the radio link failure recovery method according to the first aspect, the performing, by the UE, a change operation from a dual active protocol stack to a single active protocol stack includes one or more of the following:

operation 1: resetting a Medium Access Control entity (MAC) corresponding to the source base station and releasing the MAC configuration of the source base station;

operation 2: for each DAPS bearer, a Radio Link Control (RLC) entity and an associated logical channel of the source base station are released, and a Packet Data Convergence Protocol (PDCP) entity is reconfigured to release a DAPS (i.e., a PDCP entity configured with a DAPS (called a DAPS PDCP entity) is reconfigured to be a normal non-PDCP entity (a PDCP entity not configured with a DAPS));

operation 3: for each Signaling Radio Bearer (SRB), releasing the PDCP entity of the source base station, and releasing the RLC entity of the source base station and its associated logical channel;

and operation 4: releasing the physical channel configuration of the source base station;

operation 5: the security key used at the source base station is discarded.

In the radio link failure recovery method according to the first aspect, when the UE configured with the DAPS bearer determines that the radio link failure RLF is not monitored in the link with the source base station, the UE falls back to a single active protocol stack state where connection is maintained only with the source base station, including performing one or more of the following operations:

operation 1: releasing the configuration of the target base station;

operation 2: resetting the MAC corresponding to the target base station and releasing the MAC configuration of the target base station;

operation 3: for each DAPS bearer, releasing the RLC entity and its associated logical channel of the target base station, reconfiguring the PDCP release to release the DAPS (i.e., reconfiguring the DAPS PDCP entity to be a normal non-PDCP entity);

and operation 4: for each SRB, releasing the PDCP entity of the target base station, releasing the RLC entity of the target base station and a logic channel associated with the RLC entity, and if a master key update indication (such as a masterKeyUpdate information element indication) is not received, configuring the PDCP entity of the source base station as continuation (continuation) of the state variable of the PDCP entity of the target base station;

operation 5: for each Data Radio Bearer (DRB) not configured as a DAPS Bearer, if a master key update indication (e.g., a masterKeyUpdate information element indication) is not received, configuring the PDCP entity of the source base station as a continuation (termination) of the state variable of the PDCP entity of the target base station;

operation 6: releasing the physical channel configuration of the target base station;

operation 7: discarding the security key used at the target base station;

operation 8: loss of any saved RRC messages; resuming the suspended SRB at the source base station;

operation 9: for each non-DAPS bearer, fallback to the UE configuration used in the DRB of the source base station (including PDCP, RLC state variables, security configuration, data stored in the transmit and receive buffers of the PDCP and RLC entities);

operation 10: fallback to the measurement configuration used by the UE at the source base station.

Operation 11: a failure information procedure is initiated to report to the network side that RLF occurred at the target base station with DAPS configured. Preferably, in the process of the failure information, a failure reason included in an RRC message (e.g., a failure information FailureInformation message) for reporting the failure information is set to be an MCG RLF configured with a DAPS.

In the radio link failure recovery method of the first aspect, the UE generating the MCG RLF occurs after the UE successfully completes the DAPS handover to the target base station.

In the radio link failure recovery method according to the first aspect, when the link between the UE configured with the DAPS bearer and the source base station monitors that RLF occurs, the UE initiates an RRC connection reestablishment procedure.

In the radio link failure recovery method according to the first aspect, the UE performs the operation of changing from the dual active protocol stack to the single active protocol stack when receiving an RRC message including indication information for releasing the source base station from the network side.

In the radio link failure recovery method according to the first aspect, a UE sends an RRC message including DAPS indication information to a network side, where the DAPS indication information is used to indicate that the UE is configured with a DAPS bearer; preferably, the RRC message is an RRC reestablishment request message or an RRC reestablishment request complete message.

In the radio link failure recovery method of the first aspect, the UE configured with the DAPS bearer is that one or more DRBs of the UE are configured with a DAPS configuration information element for indicating to perform a DAPS handover operation.

In the radio link failure recovery method according to the first aspect, when the UE monitors that the RLF occurs in the link of the source base station, the UE performs one or more of the following operations:

operation 1: resetting the MAC corresponding to the source base station and releasing the MAC configuration of the source base station;

operation 2: for each DAPS bearer, releasing the RLC entity and the associated logical channel of the source base station, and reconfiguring PDCP release to release the DAPS (namely reconfiguring the PDCP entity configured with the DAPS (called the DAPS PDCP entity) into a normal non-PDCP entity (the PDCP entity not configured with the DAPS));

operation 3: for each SRB, releasing a PDCP entity of the source base station, and releasing an RLC entity of the source base station and a logic channel associated with the RLC entity;

and operation 4: releasing the physical channel configuration of the source base station;

operation 5: the security key used at the source base station is discarded.

According to a second 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 of a protocol stack associated with a DAPS bearer in a dual active protocol stack configuration.

Fig. 3 is a flowchart showing a radio link failure recovery method according to embodiment 1.

Fig. 4 shows a block diagram of a user equipment UE to which the present disclosure relates.

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 be updated or not updated accordingly. The security includes encryption and decryption and integrity protection. The source Cell may also be referred to as a source base station, or a source beam (beam), a source Transmission point (TRP), a source Primary Cell (PCell), a source Primary Cell group MCG; the target cell may also be referred to as a target base station, or target beam, target transmission point, target primary cell PCell, target cell group MCG. The source cell refers to a cell serving the UE, which is connected before the handover procedure is initiated, i.e., a cell that sends an RRC message containing a handover command to the UE. 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 the target cell identifier included in 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 may include 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 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. Monitoring (monitor) and detection (detect) may be replaced.

The following describes processes or concepts in the prior art to which the present disclosure relates.

Handover configuration in NR system:

in the NR system, the RRC reconfiguration message for the handover command carries the RRC configuration from the target base station, including but not limited to the following RRC configurations (see section 6.2.2 in 3GPP technical standard protocol 38.331):

-measurement configuration (measconfig information element): for configuring intra-frequency, inter-frequency and inter-radio access technology measurements performed by the UE. Such as measurement object configuration, measurement reporting configuration, measurement gap (gap) configuration, etc.

-a cell group configuration (cellGroupConfig information element) for configuring the master cell group or the secondary cell group. Including RLC bearer configuration corresponding to DRB/SRB

(rlc-bearritoaddmodlist information element and rlc-beartorbeeselist information element), MAC configuration (MAC-cell group pconfig information element), physical layer configuration, secondary cell addition/modification/release configuration, Special cell (SpCell) configuration, and the like. The scell configuration includes a cell index number, handover information (serving cell information element), Radio Link failure related timer and constant configuration, Radio Link Monitoring (RLM) configuration, special cell dedicated configuration, and the like. The reconfigurationwitthsync information element is similar to the mobile control information in the LTE system, and includes handover-related information to realize mobility, which includes serving cell configuration common information, C-RNTI of the UE in the target cell, handover process monitoring timer T304 configuration, random access dedicated configuration for random access process to the target cell, and the like.

-non access stratum specific information (dedicatedinfonsulst information element).

-a radio bearer configuration (radiobeareconfig information element) for configuring a Service Data Application Protocol (SDAP) layer and a PDCP of the radio bearers DRB and/or SRB.

Master key update configuration (masterKeyupdate information element).

Other configurations (otherconfig information elements) for configuring a report-near configuration (reportproximitionconfig information element), an In-Device Coexistence (IDC) configuration, an energy selection indication configuration (powerprefinedication configuration information element), a location acquisition configuration (obatinlocationconfig information element), and the like.

General handover procedure in LTE/NR systems:

the mobility of the connected user is mainly achieved through a handover procedure, i.e. a procedure in which the UE in the RRC connected state changes a serving cell (primary 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 current 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.

And (3) DAPS handover:

release 16 introduced DAPS handover, which refers to a handover procedure in which a UE maintains a connection with a source base station after receiving an RRC message for handover, until the source base station is released after successfully performing a random access procedure to a target. In the process, the UE continues to receive downlink data from the source base station until the source base station is released, and the user continues to send uplink data to the source base station until the random access process to the target base station is successfully completed. After the random access process to the target base station is completed, the MAC layer indicates the completion of the random access process to the upper layer, and after receiving the indication, the RRC layer indicates the lower layer (such as the PDCP layer) to execute uplink data change and change an uplink path from the source base station to the target base station. When the PDCP layer is requested to change uplink Data, a PDCP layer PDCP Data Protocol Data Unit (PDU) PDU is delivered to an RLF entity associated with the target base station, a PDCP control PDU associated with the source base station is delivered to an RLC entity associated with the source base station, and a PDCP control PDU associated with the target base station is delivered to an RLC entity associated with the target base station.

Under the condition of DAPS handover, after receiving a handover command, the UE establishes an MAC entity for a target base station, if a DRB is configured as a DAPS bearer, establishes an RLC entity and a Dedicated Traffic Channel (DTCH) logical Channel associated with the target base station for the DRB, and reconfigures the PDCP entity associated with the DAPS bearer as a DAPS PDCP entity, namely, the DAPS PDCP entity has a security and robustness Header Compression (ROHC) function respectively associated with the source base station and the target base station in the PDCP entity, and respectively associates the security and ROHC functions with corresponding RLC entities configured by the source base station and the target base station. In the above manner, during the DAPS handover, the UE simultaneously maintains the active protocol stacks for the source base station and the target base station, as shown in fig. 2.

In the course of DAPS, if the source base station fails in radio link, the UE suspends the transmission of DRBs of all source base stations and releases the connection of the source base station. After the DAPS handover is completed, the UE receives an RRC reconfiguration message sent from the target base station, where the RRC reconfiguration message carries indication information (e.g., identified by a DAPS-SourceRelease information element) for indicating a release of the source base station, and after receiving the indication, the UE performs an operation of releasing the configuration of the source base station and the protocol stack. The operations include one or more of: resetting the MAC corresponding to the source base station and releasing the MAC configuration of the source base station; for each DAPS bearer, releasing the RLC entity and the associated logical channel of the source base station, and reconfiguring PDCP release to release the DAPS (namely reconfiguring the PDCP entity configured with the DAPS (called the DAPS PDCP entity) into a normal non-PDCP entity (the PDCP entity not configured with the DAPS)); for each SRB, releasing a PDCP entity of the source base station, and releasing an RLC entity of the source base station and a logic channel associated with the RLC entity; releasing the physical channel configuration of the source base station; the security key used at the source base station is discarded.

When the DAPS handover fails, that is, the T304 timer for monitoring the handover process is overtime, if the radio link failure is not monitored on the source base station, the UE returns to the connection with the source base station, and reports the DAPS handover failure through the source base station without triggering the RRC connection re-establishment process. In returning to the connection with the source base station, the UE reverts from the DAPS state to a single active protocol stack state that maintains communication only with the source base station by performing one or more of the following: releasing the configuration of the target base station; resetting the MAC corresponding to the target base station and releasing the MAC configuration of the target base station; for each DAPS bearer, releasing the RLC entity and its associated logical channel of the target base station, reconfiguring the PDCP release to release the DAPS (i.e., reconfiguring the DAPS PDCP entity to be a normal non-PDCP entity); for each SRB, releasing the PDCP entity of the target base station, releasing the RLC entity of the target base station and a logic channel associated with the RLC entity, and if the master key updating instruction is not received, configuring the PDCP entity of the source base station as continuation (termination) of the state variable of the PDCP entity of the target base station; releasing the physical channel configuration of the target base station; discarding the security key used at the target base station; loss of any saved RRC messages; resuming the suspended SRB at the source base station; for each non-DAPS bearer, fallback to the UE configuration used in the DRB of the source base station (including PDCP, RLC state variables, security configuration, data stored in the transmit and receive buffers of the PDCP and RLC entities); fallback to the measurement configuration used by the UE at the source base station.

Radio Link Failure (RLF):

the UE considers that RLF occurs when: the timer T310 for RLF monitoring times out, the timer T312 for fast RLF monitoring times out, receipt of random access problems from the MAC layer only and receipt of an indication from the RLC entity indicating that the number of retransmissions reaches a maximum. When the DAPS is switched, if the timer, the MAC entity and the RLC are associated with the source base station MCG, the source base station MCG RLF is considered to be monitored; and if the timer, the MAC entity and the RLC are associated with the target base station MCG, the target base station MCG RLF is considered to be monitored. In Dual Connectivity (DC), the UE is configured with a Secondary Cell Group (SCG), and if the timer, the MAC entity and the RLC are associated with the SCG, the UE is considered to monitor the SCG RLF.

The following two scenarios are considered in this disclosure:

scene 1: after the DAPS handover is successful, the UE generates a radio link failure RLF, which refers to a link failure of the PCell after the handover is successful, or a link failure of a target cell for the DAPS handover. At this time, the link between the UE and the source base station is also in the RLF state, and the RLF of the source link may occur during the DAPS handover procedure (T304 is running) or after the DAPS handover procedure is successfully completed, that is, the random access procedure of the UE to the target base station is successfully completed.

Scene 2: after the DAPS handover is successful, the UE generates a radio link failure RLF, which refers to a link failure of the PCell after the handover is successful, or a link failure of a target cell for the DAPS handover. At this time, the link between the UE and the source base station is not in the RLF state, i.e., the link quality state of the source link is good.

In the above two cases, the UE needs to fall back from the DAPS state, i.e. the dual active protocol stack state, to the single active protocol stack state to continue the next operation, e.g. performing the RRC connection re-establishment procedure. Otherwise, when the UE in the DAPS state executes the connection recovery process with the network side under the RLF in the two scenarios, the network side cannot know whether the UE is in the DAPS state, and the states of the UE and the network side are not matched, which may cause the RRC reconfiguration failure after the connection recovery process of the UE fails. The present disclosure provides a solution to the above-described problem on the basis of the above-described scenario, but is not limited to the above-described scenario.

Example 1:

this embodiment presents a method (as shown in fig. 3) for the UE to autonomously perform fallback from the DAPS state to the single active protocol stack (non-DAPS) state during RRC connection re-establishment.

Step 1: the UE initiates an RRC reestablishment procedure.

Preferably, the UE may initiate the RRC reestablishment procedure when one of the following conditions is satisfied: that is, in step 0, when the occurrence of RLF of MCG is detected; when an RLF is detected for the MCG and the timer 316 is not configured; when the synchronous reconfiguration of the MCG fails, the switching fails. When the UE configures the DAPS, the RLF of the MCG refers to the RLF of the target base station after receiving the handover command or after the handover is successful. The handover success refers to the successful completion of random access between the MAC layer and the target base station as described above. The timer T316 is configured to monitor an MCG failure information process (or referred to as a fast MCG recovery process), start the timer T316 when the UE sends an MCG failure information message or triggers the MCG failure information process, stop the timer T316 when a response message such as an RRC reconfiguration message or an RRC release message is received from the network side, or when an RRC connection reestablishment process is initiated, and when the timer T316 is overtime, the UE considers that the MCG failure information process has failed to end, and at this time, the UE may execute an RRC reestablishment process.

Step 2: in the RRC reestablishment procedure, for example, in an initialization phase of the RRC reestablishment procedure, the UE performs an operation of falling back from the DAPS state to a single active protocol stack (non-DAPS) state, and releases the protocol stack and configuration associated with the source base station. The operations include one or more of:

operation 1: resetting the MAC corresponding to the source base station and releasing the MAC configuration of the source base station;

operation 2: for each DAPS bearer, releasing the RLC entity and the associated logical channel of the source base station, and reconfiguring PDCP release to release the DAPS (namely reconfiguring the PDCP entity configured with the DAPS (called the DAPS PDCP entity) into a normal non-PDCP entity (the PDCP entity not configured with the DAPS));

operation 3: for each SRB, releasing a PDCP entity of the source base station, and releasing an RLC entity of the source base station and a logic channel associated with the RLC entity;

and operation 4: releasing the physical channel configuration of the source base station;

operation 5: the security key used at the source base station is discarded.

The UE performs the above operations when a DAPS is configured, and the DAPS configured for the UE may also be described as the UE being configured with any one or more DAPS bearers; or any one or more DRBs of the UE are configured with a DAPS (as identified with a DAPS-Config information element). The DAPS bearer means that the bearer DRB is configured with an information element for indicating a DAPS configuration, such as a DAPS-config information element. Preferably, the daps-config information element is configured separately for each DRB.

Example 2:

the embodiment provides a method for indicating the UE to return from the DAPS state to the single-activation protocol stack (non-DAPS) state in the RRC connection reestablishment process by the network side through a displayed RRC signaling mode based on the DAPS information reported by the UE.

Step 1: the UE initiates an RRC reestablishment procedure.

The triggering of the UE initiating the RRC reestablishment procedure is as described in embodiment 1.

Step 2: in the RRC reestablishment process, the UE carries a DAPS indication message in the RRC connection reestablishment request message or the RRC connection reestablishment complete message, so as to indicate to the network side that the UE is configured with a DAPS, or that the UE is configured with any one or more DAPS bearers.

And step 3: an RRC message containing an information element for indicating release of the source base station is received from the base station. The RRC message may be an RRC connection re-establishment message or an RRC reconfiguration message. Preferably, the RRC reconfiguration message is a first RRC reconfiguration message after completion of the RRC reestablishment procedure. Preferably, the DAPS-sourcerelease information element used for instructing the release of the information element of the source base station is used for instructing the UE to release the source base station, and includes a source cell portion for stopping the DAPS operation and a source cell portion for releasing the DAPS configuration. Preferably, the information element for indicating the release source base station may also be described as information element for indicating the release source base station is set to TRUE or 1.

In this step, after the UE receives the RRC message including the above information element, the UE performs an operation of fallback from the DAPS state to a single active protocol stack (non-DAPS) state, and releases the protocol stack and configuration associated with the source base station. The operations include one or more of:

operation 1: resetting the MAC corresponding to the source base station and releasing the MAC configuration of the source base station;

operation 2: for each DAPS bearer, releasing the RLC entity and the associated logical channel of the source base station, and reconfiguring PDCP release to release the DAPS (namely reconfiguring the PDCP entity configured with the DAPS (called the DAPS PDCP entity) into a normal non-PDCP entity (the PDCP entity not configured with the DAPS));

operation 3: for each SRB, releasing a PDCP entity of the source base station, and releasing an RLC entity of the source base station and a logic channel associated with the RLC entity;

and operation 4: releasing the physical channel configuration of the source base station;

operation 5: the security key used at the source base station is discarded.

The UE performs the above operations when a DAPS is configured, and the DAPS configured for the UE may also be described as the UE being configured with any one or more DAPS bearers; or any one or more DRBs of the UE are configured with a DAPS (as identified with a DAPS-Config information element). The DAPS bearer means that the bearer DRB is configured with an information element for indicating a DAPS configuration, such as a DAPS-config information element. Preferably, the daps-config information element is configured separately for each DRB.

Example 3:

this embodiment presents a method for the UE to perform fallback from the DAPS state to the single active protocol stack (non-DAPS) state and to the connection with the source base station in order to avoid initiating the RRC connection reestablishment procedure in case of scenario 2 above.

Step 1: the UE monitors that RLF of MCG occurs.

The MCG refers to a target MCG at DAPS handover.

Step 2: if the source base station does not monitor the RLF, the UE releases the target base station part of the DAPS operation and executes the operation of returning from the DAPS state to the single activation protocol stack (non-DAPS) state. The operations include one or more of:

operation 1: releasing the configuration of the target base station;

operation 2: resetting the MAC corresponding to the target base station and releasing the MAC configuration of the target base station;

operation 3: for each DAPS bearer, releasing the RLC entity and its associated logical channel of the target base station, reconfiguring the PDCP release to release the DAPS (i.e., reconfiguring the DAPS PDCP entity to be a normal non-PDCP entity);

and operation 4: for each SRB, releasing the PDCP entity of the target base station, releasing the RLC entity of the target base station and a logic channel associated with the RLC entity, and if a master key update indication (such as a masterKeyUpdate information element indication) is not received, configuring the PDCP entity of the source base station as continuation (continuation) of the state variable of the PDCP entity of the target base station;

operation 5: for each DRB which is not configured to be carried by the DAPS, if a master key update indication (such as a masterKeyUpdate information element indication) is not received, configuring the PDCP entity of the source base station as the continuation (termination) of the state variable of the PDCP entity of the target base station;

operation 6: releasing the physical channel configuration of the target base station;

operation 7: discarding the security key used at the target base station;

operation 8: loss of any saved RRC messages; resuming the suspended SRB at the source base station;

operation 9: for each non-DAPS bearer, fallback to the UE configuration used in the DRB of the source base station (including PDCP, RLC state variables, security configuration, data stored in the transmit and receive buffers of the PDCP and RLC entities);

operation 10: fallback to the measurement configuration used by the UE at the source base station.

Operation 11: a failure information procedure is initiated to report to the network side that RLF occurred at the target base station with DAPS configured. Preferably, in the process of the failure information, a failure reason included in an RRC message (e.g., a failure information FailureInformation message) for reporting the failure information is set to be an MCG RLF configured with a DAPS.

Before step 1, it also includes that the UE successfully completes the DAPS handover, that is, in case that the UE is configured with any DAPS bearer, the MAC layer successfully completes the random access procedure to the target base station, and at this time, T304 is not in a running state. I.e. step 2 is performed when the UE is configured with any one or more DAPS bearers.

Example 4:

this embodiment presents a method in which the UE performs fallback from the DAPS state to a single active protocol stack (non-DAPS) state in case of RLF at the source base station.

Step 1: the source RLF in the DAPS procedure occurs, that is, when the UE is configured with any one of the DAPS bearers, the UE monitors the RLF of the source MCG.

Step 2: a fallback from the DAPS state to a single active protocol stack (non-DAPS) state is performed, releasing the configuration and protocol stack of the source base station. The operations include one or more of:

operation 1: suspending transmission of DRBs of all source base stations;

operation 2: releasing the connection of the source base station;

operation 3: resetting the MAC corresponding to the source base station and releasing the MAC configuration of the source base station;

and operation 4: for each DAPS bearer, releasing the RLC entity and the associated logical channel of the source base station, and reconfiguring PDCP release to release the DAPS (namely reconfiguring the PDCP entity configured with the DAPS (called the DAPS PDCP entity) into a normal non-PDCP entity (the PDCP entity not configured with the DAPS));

operation 5: for each SRB, releasing a PDCP entity of the source base station, and releasing an RLC entity of the source base station and a logic channel associated with the RLC entity;

operation 6: releasing the physical channel configuration of the source base station;

operation 7: the security key used at the source base station is discarded.

It is to be noted that this embodiment is not limited to the foregoing scenario 1 and scenario 2 of the present disclosure, but is also applicable to the case of the source base station RLF where the DAPS is not completed yet, i.e., T304 is running.

Example 5:

this example corresponds to example 2 and presents a corresponding method on the base station side.

Step 1: in the RRC reestablishment process, an RRC connection reestablishment request message or an RRC connection reestablishment complete message is received from the UE and carries a DAPS indication information, which is used for the UE to indicate to the network side that the UE is configured with a DAPS, or that the UE is configured with any one or more DAPS bearers.

Step 2: transmitting an RRC message including an information element for indicating release of the source base station to the UE. The RRC message may be an RRC connection re-establishment message or an RRC reconfiguration message. Preferably, the RRC reconfiguration message is a first RRC reconfiguration message after completion of the RRC reestablishment procedure. Preferably, the DAPS-sourcerelease information element used for instructing the release of the information element of the source base station is used for instructing the UE to release the source base station, and includes a source cell portion for stopping the DAPS operation and a source cell portion for releasing the DAPS configuration. Preferably, the information element for indicating the release source base station may also be described as information element for indicating the release source base station is set to TRUE or 1.

In this step, the instruction releases the information element of the source base station, so that the UE performs an operation of fallback from the DAPS state to a single active protocol stack (non-DAPS) state after receiving the information element, and releases a protocol stack and a configuration associated with the source base station. The operations include one or more of:

operation 1: resetting the MAC corresponding to the source base station and releasing the MAC configuration of the source base station;

operation 2: for each DAPS bearer, releasing the RLC entity and the associated logical channel of the source base station, and reconfiguring PDCP release to release the DAPS (namely reconfiguring the PDCP entity configured with the DAPS (called the DAPS PDCP entity) into a normal non-PDCP entity (the PDCP entity not configured with the DAPS));

operation 3: for each SRB, releasing a PDCP entity of the source base station, and releasing an RLC entity of the source base station and a logic channel associated with the RLC entity;

and operation 4: releasing the physical channel configuration of the source base station;

operation 5: the security key used at the source base station is discarded.

The UE performs the above operations when a DAPS is configured, and the DAPS configured for the UE may also be described as the UE being configured with any one or more DAPS bearers; or any one or more DRBs of the UE are configured with a DAPS (as identified with a DAPS-Config information element). The DAPS bearer means that the bearer DRB is configured with an information element for indicating a DAPS configuration, such as a DAPS-config information element. Preferably, the daps-config information element is configured separately for each DRB.

Example 6

This embodiment explains the user equipment UE 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. The instructions, when executed by the processor 401, may perform the various methods of radio link failure recovery upon DAPS bearer described in detail above in this disclosure.

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.