CN111866965A

CN111866965A - Condition switching method and corresponding user equipment

Info

Publication number: CN111866965A
Application number: CN201910353716.2A
Authority: CN
Inventors: 常宁娟; 刘仁茂
Original assignee: Sharp Corp
Current assignee: Sharp Corp
Priority date: 2019-04-28
Filing date: 2019-04-28
Publication date: 2020-10-30
Anticipated expiration: 2039-04-28
Also published as: CN111866965B; WO2020221193A1

Abstract

The present disclosure provides a conditional handover method performed by a user equipment and a corresponding user equipment. A conditional handover method performed by a user equipment, comprising the steps of: a condition switching monitoring step, in which User Equipment (UE) receives a Radio Resource Control (RRC) message containing a condition switching command from a source base station, stores condition switching configuration in the condition switching command, and monitors whether the switching condition is met according to the switching condition; a conditional switch execution step, when the UE monitors that the switch condition in the stored conditional switch configuration is satisfied, the conditional switch is initiated; an RRC message receiving step, wherein the UE which is executing the condition switching receives the RRC message from the source base station; a conditional switch stopping step in which the UE stops an ongoing conditional switch process; and executing RRC configuration, wherein the UE executes corresponding configuration according to the configuration in the RRC message received in the ongoing conditional switching process.

Description

Condition switching method and corresponding user equipment

Technical Field

The present disclosure relates to the field of wireless communication technologies, and in particular, to a conditional handover method and a corresponding 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 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 0 ms or close to 0 ms 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. And the UE executes the switching according to the switching command received before when the configured condition is met. 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 the UE handles the reception of an RRC message from the source cell in the process of performing a conditional handover. The embodiment of the disclosure provides a conditional switching method executed by user equipment and corresponding user equipment.

According to a first aspect of the present disclosure, a conditional handover method performed by a user equipment is provided, which includes the following steps: a condition switching monitoring step, in which User Equipment (UE) receives a Radio Resource Control (RRC) message containing a condition switching command from a source base station, stores condition switching configuration in the condition switching command, and monitors whether the switching condition is met according to the switching condition; a conditional switch execution step, when the UE monitors that the switch condition in the stored conditional switch configuration is satisfied, the conditional switch is initiated; an RRC message receiving step, wherein the UE which is executing the condition switching receives the RRC message from the source base station; a conditional switch stopping step in which the UE stops an ongoing conditional switch process; and executing RRC configuration, wherein the UE executes corresponding configuration according to the configuration in the RRC message received in the ongoing conditional switching process.

In the above-described conditional access method performed by the user equipment, it is preferable that the RRC message from the source base station received by the UE performing the conditional access includes: case 1: the RRC message comprises a handover command; case 2: the RRC message comprises configuration information for conditional handover, and the configuration information for conditional handover comprises indication information for releasing a target cell of a handover process currently performed by the UE; case 3: the RRC message comprises configuration information for conditional handover, and the configuration information for conditional handover comprises modification information related to a target cell of a handover process currently performed by the UE; case 4: the RRC message comprises configuration information for conditional switching, and the configuration information for conditional switching comprises information for instructing the UE to release the stored conditional switching command configuration; case 5: the RRC message comprises configuration information for conditional handover, and the configuration information for conditional handover comprises configuration information of other conditional handover alternative cells which are irrelevant to or different from a target cell of a handover process currently performed by the UE; case 6: the RRC message contains configuration information that is not used for handover and conditional handover.

In the above-mentioned conditional handover method performed by the user equipment, it is preferable that the performing RRC configuration step is performed after the performing RRC configuration step is performed, or the performing RRC configuration step is performed after the performing RRC configuration step is performed.

In the above-mentioned conditional handover method performed by the user equipment, in case 3, preferably, the performing the RRC configuration step after performing the RRC message receiving step includes: the UE suspends the current ongoing conditional switching process; determining whether a handover condition of a reconfiguration associated with the target cell associated with the ongoing conditional handover in the conditional handover configuration in the received RRC message is still met.

In the above-mentioned conditional handover method performed by the UE, preferably, when it is determined that the handover condition associated with the reconfiguration of the target cell associated with the ongoing conditional handover in the conditional handover configuration in the received RRC message is still satisfied, the UE continues the ongoing conditional handover, otherwise, the UE performs the conditional handover stopping step to stop the ongoing conditional handover process.

In the above conditional handover method by the user equipment, it is preferable that in the conditional handover stop step, the UE performs one or more of the following operations to stop the ongoing conditional handover procedure: operation 1: stopping the timer or considering the timer to be overtime; operation 2: stopping the ongoing random access procedure; operation 3: canceling the sending of the RRC reconfiguration complete message in the conditional switching execution step; and operation 4: releasing the RRC entity associated with the target cell; operation 5: generating failure report information, and including the failure report information in a response message sent to a source base station or a response message sent to a target base station; operation 6: the conditional switch process is considered to be over.

According to a second aspect of the present disclosure, a conditional handover method performed by a user equipment is proposed, which includes the steps of: a condition switching monitoring step, in which User Equipment (UE) receives a Radio Resource Control (RRC) message containing a condition switching command from a source base station, stores condition switching configuration in the condition switching command, and monitors whether the switching condition is met according to the switching condition; a conditional switch execution step, when the UE monitors that the switch condition in the stored conditional switch configuration is satisfied, the conditional switch is initiated; an RRC message receiving step, wherein the UE which is executing the condition switching receives the RRC message from the source base station; and the conditional switching continues to execute the step, and the UE does not apply or execute the RRC message received in the ongoing conditional switching process to continue the ongoing conditional switching process.

In the above-mentioned conditional handover method performed by the user equipment, it is preferable that in the conditional handover continuation performing step, the UE performs one or more of the following methods not to apply or not to perform the RRC message received in the ongoing conditional handover procedure to continue the ongoing conditional handover procedure: when receiving the RRC message from the source base station, the RRC layer ignores or discards the received RRC message; when the MAC layer receives a logical channel identification indicating that the MAC protocol data unit PDU or the service data unit SDU corresponds to the dedicated control channel DCCH, the MAC layer discards the MAC PDU or the MAC SDU.

In the above-mentioned conditional handover method performed by the user equipment, it is preferable that the conditional handover configuration and the handover condition are associated with a target cell.

According to a third aspect of the present disclosure, a user equipment is provided, comprising: a processor; and a memory having instructions stored thereon; the instructions, when executed by the processor, cause the user equipment to perform the conditional switching method described above.

According to the conditional handover method executed by the user equipment and the corresponding user equipment, the time delay and signaling overhead caused by incorrect handover or handover failure can be avoided and the mobility performance of the system can be optimized under the condition that the UE initiates the conditional handover process of accessing to the target base station and receives the RRC configuration message from the source base station. In other words, the data interruption delay of "0 ms" can be satisfied as much as possible in the mobile handover procedure, and the robustness of the handover is improved to meet the mobility requirement of the seamless handover in NR.

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 flow chart of a general handover procedure in an LTE/NR system.

Fig. 2 is a schematic diagram of a conditional handover method performed by a user equipment UE according to embodiment 1 of the present disclosure.

Fig. 3 is a flowchart of a conditional handover method performed by a user equipment UE according to embodiment 1 of the present disclosure.

Fig. 4 is a schematic diagram of a conditional handover method performed by a user equipment UE according to embodiment 2 of the present disclosure.

Fig. 5 is a flowchart of a conditional handover method performed by a user equipment UE according to embodiment 2 of the present disclosure.

Fig. 6 is a block diagram of a schematic structure of a user equipment UE according to the present disclosure.

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 LTE system that can be connected to a 5G core network), while LTE may be replaced with E-UTRAN or Evolved Universal Terrestrial Radio Access (E-UTRA). In the present disclosure, a source cell may also be referred to as a source base station, a source beam (beacon), and a source transmission point (TRP), and a target cell may also be referred to as a target base station, and a target beam and a target transmission point. The source cell refers to a base station serving the UE, which is connected before the handover procedure is initiated, i.e., a base station that sends an RRC message containing a handover command to the UE. The target cell refers to a base station 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. The handover command is used to trigger the UE to perform handover, and in the NR system is an RRC reconfiguration message containing a synchronization reconfiguration (reconfiguration with sync) information element. 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 base station, 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. The conditional switch command and the conditional switch configuration are replaceable. Monitoring (monitor) and detection (detect) may be replaced.

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

A general handover procedure in the LTE/NR system is first briefly described. 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. The process is shown in FIG. 1 and briefly described as follows:

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 random access procedure, connection before disconnection (mbe) and the like, all aim to reduce data interruption time in the handover procedure.

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). 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 to the UE in advance before a real handover condition (corresponding to the conservative measurement report threshold) is met, wherein the handover execution condition is carried. Different from the existing LTE handover mechanism, after receiving a handover command, the UE does not immediately perform handover, but stores the received handover command configuration, and monitors the link quality of the source cell or the link quality of the target cell according to the handover condition carried in the handover command message. And only when the configured switching condition is monitored to be met, the UE starts to execute the stored switching command and accesses to the target cell. For the above switching mechanism, the present disclosure refers to conditional switching, but the name is not limited thereto, and may refer to a switching mechanism of an early switching command, a pre-switching, an early switching preparation, and the like.

A conclusion is reached on a conditional switch over 3GPP RAN2 workgroup conference: and after the UE initiates the condition switching, before the RRC reconfiguration complete message is successfully sent to the target base station, the source cell maintains the RRC connection of the UE. In other words, the UE still maintains the RRC connection with the source base station before successfully sending the RRC reconfiguration complete message to the target base station. In the conditional handover, when to initiate the handover execution phase is determined by the UE, and the source base station serving the UE cannot know in time, which may be the case where the UE has initiated the conditional handover procedure to access the target base station but has received the RRC configuration message from the source base station. The present disclosure provides the following implementation method for the problem of how to operate the UE under such a condition, so that the UE can process the received RRC message under such a condition, thereby avoiding the delay and signaling overhead caused by incorrect handover or handover failure, and optimizing the mobility performance of the system. When the UE has an ongoing conditional handover procedure (i.e. before initiating the conditional handover procedure and successfully sending the RRC reconfiguration complete message to the target base station, at this time, T304 is in an operating state), the receiving of the RRC configuration message from the source base station includes, but is not limited to, the following several cases:

Case 1: the RRC message includes a handover command. The handover command is a conventional handover command, i.e. not a handover command for conditional handover.

Case 2: the RRC message includes configuration information for conditional handover, and the configuration information for conditional handover includes indication information for releasing a target cell of a handover procedure currently performed by the UE. In other words, the target cell of the conditional handover process currently being executed by the UE and the conditional handover candidate cell indicated to be released in the conditional handover configuration in the RRC message are the same; or the target cell of the conditional handover process currently executed by the UE is one of the multiple conditional handover alternative cells indicated to be released in the conditional handover configuration in the RRC message.

Case 3: the RRC message includes configuration information for conditional handover, and the configuration information for conditional handover includes modification information related to a target cell of a handover procedure currently performed by the UE, such as reconfiguration information of an associated condition. In other words, the RRC message includes reconfiguration information of the target cell related configuration of the conditional handover procedure currently being performed by the UE.

Case 4: the RRC message includes configuration information for conditional handover, and the configuration information for conditional handover includes information for disabling conditional handover or instructing the UE to release the saved conditional handover command configuration.

Case 5: the RRC message includes configuration information for conditional handover, and the configuration information for conditional handover includes configuration information of other conditional handover candidate cells that are not related to or different from a target cell of a handover process currently performed by the UE. In other words, the RRC message is configuration information for configuring or modifying other conditional handover candidate cells.

Case 6: the RRC message contains configuration information that is not used for handover and conditional handover. For example, the RRC message is not RRC reconfiguration information, or the RRC message is RRC reconfiguration information that does not include a synchronization reconfiguration information element or a mobility control information element. That is, the RRC message is not used for handover, such as addition modification for configuring a secondary cell.

The conditional handover candidate cell refers to a conditional handover command in an RRC message received by the UE for configuring conditional handover or a (target) cell in a conditional handover configuration. The network side can configure one or more handover condition candidate cells for the UE at the same time.

The following are several embodiments of the present disclosure performed on a UE based on the above issues.

Example 1

In this embodiment, when the UE performing conditional handover receives an RRC message from the source base station, the UE stops the ongoing conditional handover procedure, applies or performs the received RRC message. Where a conditional switch is being performed may also be described as a conditional switch being initiated. This process is described below using fig. 2 and 3.

Step S301: the conditional switch is initiated (conditional switch execution step).

The initiating conditional switch is initiated when the UE monitors that a switch condition in the saved conditional switch configuration is satisfied. The conditional handover configuration and the handover condition are associated with a target cell. Preferably, the operation of initiating the conditional switch comprises 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.

In one embodiment, the UE may maintain two sets of access layer protocol stacks (user plane protocol stacks or control plane protocol stacks) for the source cell and the target cell simultaneously during the handover process. At this time, the operation of initiating the conditional handover further includes establishing an associated L1/L2 entity or RRC entity for the target cell. The L2 entity includes a Service Data Adaptation Protocol (SDAP) entity, a Packet Data Convergence Protocol (PDCP) entity, a Radio Link Control (RLC) entity, or a Medium Access Control (MAC) entity. One or more of the operations of initiating the conditional handover by the UE are performed in the RRC entity associated with the target cell, for example, the operations of generating the RRC reconfiguration complete message and submitting the RRC reconfiguration complete message to the lower layer for transmission are performed in the RRC entity associated with the target cell, and the operations of performing the random access to the target cell are performed in the MAC entity associated with the target cell.

Step S302: the UE that is performing the conditional handover receives an RRC message from the source base station (RRC message receiving step).

The RRC message contains the aforementioned 6 cases.

Step S303: the UE performs one or more of the following operations to stop the ongoing conditional handover procedure (conditional handover stop step).

Operation 1: the timer T304 is stopped or T304 is considered to have timed out.

Operation 2: the ongoing random access procedure is stopped. Optionally, the stopping of the ongoing random access procedure is achieved by resetting or releasing the MAC entity. Preferably, the MAC entity is a MAC entity associated with the target cell.

Operation 3: the transmission of the RRC reconfiguration complete message in step S301 is cancelled. Preferably, the sending of the RRC reconfiguration cancel complete message is implemented by reestablishing or releasing the L2 entity corresponding to the SRB 1. The L2 entity is a PDCP entity or a radio link control, RLC, entity. Preferably, the L2 entity is an L2 entity associated with the target cell, or an L2 entity associated with the target cell established in step S301.

And operation 4: and releasing the RRC entity associated with the target cell. The RRC entity is the RRC entity associated with the target cell established in step S301.

Operation 5: and generating failure report information, and including the failure report information in a response message sent to the source base station (such as in cases 2-6) or a response message sent to the target base station (such as in case 1). The failure report information includes indication information that the UE has an ongoing conditional handover procedure, a currently valid measurement result of the UE, and the like. The indication information indicating that the UE has the ongoing conditional handover procedure includes target cell information (accessed target cell identifier or frequency) associated with indicating that the UE has the initiated or ongoing conditional handover procedure when (or whether) the UE receives the RRC message in step S302 or the initiated or ongoing conditional handover procedure when the UE receives the RRC message in step S302.

Operation 6: the conditional switch process is considered to be over.

Step S304: the UE performs corresponding configuration according to the configuration in the RRC message received in step S302 (performs the RRC configuration step). Optionally, the method further includes sending a response message to the source cell in response to the RRC message received in step S302.

The execution order of step S303 and step S304 is not limited. For example, step S304 may be performed after step S303 is performed, or step S303 may be performed after step S304 is performed.

Optionally, in case 3, after performing step S302, step S304 is performed, including that the UE suspends the currently ongoing conditional switching procedure; determining whether a handover condition of a reconfiguration associated with the target cell associated with the ongoing conditional handover in the conditional handover configuration in the received RRC message is still met. If so, the UE continues the current ongoing conditional switch; if not, the UE performs step S303 to stop the ongoing conditional switch procedure. Suspending the currently ongoing conditional handover procedure by the UE refers to suspending the operation related to the handover procedure.

Obviously, this embodiment further includes, before step S301: step S300, the UE receives the RRC message containing the conditional switching command from the source base station, stores the conditional switching configuration in the conditional switching command, and monitors whether the switching condition is met according to the switching condition (a conditional switching monitoring step). The conditional handover configuration refers to an RRC configuration generated by the UE according to the configuration in the conditional handover command, and optionally, the handover configuration refers to an RRC configuration generated by the UE according to the configuration in the handover command and the RRC configuration of the current UE. The handover condition, i.e. the UE performs a handover only if the condition is met, applies the handover configuration, the handover condition being included in a conditional handover command. For example, the handover condition is a measurement event, such as measurement event a3 (neighbor cell signal quality exceeds 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 in the current 3GPP standard specifications (see section 5.5.4 in 36.331 and 38.331), such as a1 to a5, can be included as handover conditions in the conditional handover command.

Example 2

In this embodiment, when the UE performing conditional handover receives an RRC message from the source base station, the UE continues the ongoing conditional handover procedure without applying or performing the received RRC message. Where a conditional switch is being performed, it may also be described that a conditional switch is initiated or that a timer T304 for a conditional switch is running. This process is described below using fig. 4 and 5.

Step S501: the conditional switch is initiated (conditional switch execution step).

Step S502: the UE that is performing the conditional handover receives an RRC message from the source base station (RRC message receiving step).

The RRC message contains the aforementioned 6 cases.

Step S503: the UE performs one or more of the following methods without applying or performing the RRC message received in the ongoing conditional handover procedure to continue the ongoing conditional handover procedure (conditional handover continuation performing step).

In one implementation, the UE RRC layer ignores or discards the received RRC message when receiving the RRC message from the source base station. Optionally, when the UE simultaneously maintains RRC entities for the source base station and the target base station, the RRC layer is an RRC layer/entity associated with the source base station.

In another implementation, this is performed at the MAC layer. When the MAC layer receives a logical channel identifier indicating that the MAC Protocol Data Unit (PDU) or the Service Data Unit (SDU) corresponds to a Dedicated Control Channel (DCCH), the MAC layer discards the MAC PDU or the MAC SDU, i.e., does not deliver the Data Packet to the upper layer. In this manner, the MAC layer discards or does not submit packets received on SRB1 to the upper layer after initiating a random access procedure to the target cell or after initiating a conditional handover. Preferably, the MAC layer/entity is a MAC layer/entity associated with the source base station. The MAC entity learns the information of the current condition switching from an RRC layer or from the MAC entity associated with the target cell in the dual-protocol stack. In other words, after the conditional handover is initiated, an indication is sent by the MAC entity associated with the RRC layer or the target cell to the MAC entity associated with the source cell to inform that the conditional handover is ongoing or initiated.

Obviously, this embodiment further includes, before step S501: step S500, the UE receives the RRC message containing the conditional switching command from the source base station, stores the conditional switching configuration in the conditional switching command, and monitors whether the switching condition is satisfied according to the switching condition (the step of monitoring the conditional switching). The conditional handover configuration refers to an RRC configuration generated by the UE according to the configuration in the conditional handover command, and optionally, the handover configuration refers to an RRC configuration generated by the UE according to the configuration in the handover command and the RRC configuration of the current UE. The handover condition, i.e. the UE performs a handover only if the condition is met, applies the handover configuration. For example, the handover condition is a measurement event, such as measurement event a3 (neighbor cell signal quality exceeds serving cell signal quality by an offset for a duration of time). The adjacent cell corresponds to a target cell for handover.

Example 3

The UE in this embodiment does not process any RRC message from or to be sent to the source cell after initiating the conditional handover, similar to embodiment 2. Is executed on the UE. That is, during the conditional handover (timer T304 for conditional handover is running), the RRC message from the source cell or to be sent to the source cell is not processed any more.

Step 1: and initiating condition switching.

The operation and procedure for initiating the conditional switch are the same as those of the previous embodiment, and are not described herein again.

Step 2: suspend (suspend) signaling Radio Bearer 1 (signaling Radio Bearer 1, SRB 1). Optionally, reconstructing the PDCP or RLC corresponding to the SRB1 is further included. Herein, RRC refers to RRC associated with the source cell, and PDCP or RLC refers to PDCP or RLC associated with the source cell.

And step 3: after the random access procedure for accessing the target cell is completed or the transmission of the RRC reconfiguration complete message generated and transmitted to the target cell in the procedure is successful, the SRB1 is resumed. The restoring the SRB1 further includes considering the SRB1 as connected to a target cell. In another implementation, after the random access procedure for accessing the target cell is completed or after the transmission of the RRC reconfiguration complete message generated and transmitted to the target cell in the random access procedure is successful, the SRBl associated with the source base station and the associated RRC entity or L2 entity are released.

Example 4

This embodiment presents a method for conditional handover RRC procedure termination. Therefore, before the RRC process of the conditional switching is finished, the UE does not process the RRC message from the source base station even if the RRC message is received, and the ongoing conditional switching process is not interrupted. This embodiment is also applicable to handover procedures using a handover mechanism that communicates with both the source and target cells during the handover procedure (which is not a conditional handover procedure and may be referred to in this disclosure as an enhanced keep Before disconnect (eMBB) mechanism or a simultaneous connectivity handover mechanism or a dual connectivity handover mechanism or a non-split bearer handover mechanism.)

Step 1: a handover procedure is initiated. The handover procedure may be a conditional handover procedure or an eMBB handover procedure.

The operation of initiating a handover procedure for the eMBB is similar to the operation of initiating a conditional handover.

In this step, an RRC reconfiguration complete message is generated and delivered to the lower layer via SRB 1. The RRC reconfiguration complete message is sent using the new configuration (i.e., the configuration corresponding to the target cell included in the corresponding handover command).

Step 2: when the lower layer confirms the transmission (success) of the RRC reconfiguration complete message, the RRC procedure is ended, i.e., the handover procedure of the handover command RRC message is executed, and the T304 timer is stopped. The case where the lower layer confirms that the transmission of the RRC reconfiguration complete message is successful may also be expressed as the case where an indication that the RRC reconfiguration complete message transmitted from the lower layer has been transmitted (successfully) is received.

This embodiment can be expressed as follows, combining the existing mechanisms and the content of the 3GPP standard protocol.

Step 1: upon receiving the RRC reconfiguration message, the configuration in the RRC reconfiguration message is applied.

In the case of conditional handover, the receiving of the RRC reconfiguration message refers to when the handover condition is satisfied to initiate conditional handover, because the RRC reconfiguration message containing the conditional handover command is not immediately applied, but is received in advance and stored on the UE.

The applying the configuration in the RRC reconfiguration message includes generating an RRC reconfiguration complete message and delivering to the lower layer for transmission via SRB 1. The sending of the RRC reconfiguration complete message uses the new configuration (i.e. the configuration contained in the corresponding RRC reconfiguration message). Optionally, the foregoing operation of initiating the conditional switch is also included.

Step 2: if the synchronization reconfiguration with sync information element is included in the special cell configuration (scellconfig) information element and the procedure is a conditional handover or eMBB handover procedure, when the lower layer confirms the sending (success) of the RRC reconfiguration complete message, the RRC procedure is terminated, that is, the handover procedure of the handover command RRC message is executed, and the timer T304 is stopped. The lower layer may also be expressed as when an indication that the RRC reconfiguration complete message transmitted from the lower layer has been transmitted (succeeded) is received when the transmission of the RRC reconfiguration complete message transmitted from the lower layer is confirmed (succeeded). Otherwise (if the synchronization reconfiguration information element is included in the special cell configuration information element and the procedure is not a conditional handover or an eMBB handover procedure), when the MAC successfully completes a random access procedure triggered in step 1 of the RRC procedure, the RRC procedure is ended, and the timer T304 is stopped.

The above-mentioned "if the synchronization reconfiguration information element is included in the special cell configuration information element" corresponds to the NR system. The equivalent is "when mobility control information element (mobility control info) is included in RRC reconfiguration message or if MAC indicates successful reception of a physical downlink control channel with UE specific identity (e.g. cell radio network temporary identity C-RNTI) when random-access-free (skip-skip) is configured" in LTE system. Wherein the special cell configuration information element includes configuration parameters of a special cell (a primary cell PCell) of the primary cell group or a special cell (a primary and secondary cell PSCell) of the secondary cell group.

Example 5

This embodiment differs from embodiment 1 in that the UE decides to stop or continue the conditional handover procedure by determining the link condition of the source cell when it receives an RRC message from the source cell during the ongoing conditional handover procedure (T304 for conditional handover is running).

Step 1: the same as in step S301 of embodiment 1.

Step 2: the same as step S302 of embodiment 1.

And step 3: and judging whether the link of the source cell meets the condition. If not, stopping the ongoing condition switching process, namely executing the step S303 and the step S304 in the embodiment 1; if yes, continuing the ongoing conditional handover process, and not executing/discarding the RRC message received in step 2.

In one embodiment, the satisfaction of the condition specifies whether timer T310 or T312 is running. The condition is satisfied if T310 or T312 is running; if either T310 or T312 is not running, the condition is not satisfied. The T310 or T312 is used for monitoring radio link failure, which can be referred to in 3GPP protocol specification document 36.331 or 38.331.

In another embodiment, whether the condition is met refers to a channel quality measurement value, such as reference signal received power, RSRP, being below a threshold value. If the channel quality measurement value is lower than a threshold value, the condition is considered to be met; if the channel quality measurement is above a threshold, the condition is deemed not to be satisfied.

Example 6

This embodiment differs from embodiment 1 in that the UE decides to stop or continue the conditional handover procedure by judging the link condition of the target cell when it receives an RRC message from the source cell during the ongoing conditional handover procedure (T304 for conditional handover is running).

Step 1: the same as in step S301 of embodiment 1.

Step 2: the same as step S302 of embodiment 1.

And step 3: and judging whether the target cell link meets the condition. If not, continuing the ongoing conditional switching process, and not executing/discarding the RRC message received in the step 2. If so, the ongoing condition switching process is stopped, i.e., step S303 and step S304 in embodiment 1 are executed.

In another embodiment, whether the condition is met refers to a channel quality measurement, such as reference signal received power, RSRP, being above a threshold value. If the channel quality measurement value is higher than a threshold value, the condition is not satisfied; the channel quality measurement is below a threshold value, the condition is deemed satisfied.

Example 7

This embodiment provides a method for the UE to receive an RRC message from the source cell during an ongoing conditional handover procedure (T304 for conditional handover is running) and the RRC message integrity check fails.

Step 1: the same as in step S301 of embodiment 1.

Step 2: the same as step S302 of embodiment 1.

And step 3: if the bottom layer indicates that the integrity check of the RRC message in step 2 fails, the UE does not initiate an RRC connection re-establishment procedure because the UE determines that it is in an ongoing condition handover procedure.

The bottom layer indicating an integrity check failure of the RRC message may also be described as receiving an indication of an integrity check failure of the RRC message from the bottom layer.

The same applies to the SRB2 as described in the embodiments above in connection with SRB 1. The on-going conditional handover may be stated as the saved conditional handover configuration being executed, or the RRC message/configuration being executed includes a conditional handover indication/information, or T304 for conditional handover is running.

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

Fig. 6 is a block diagram of a schematic structure of a user equipment UE according to the present disclosure. As shown in fig. 6, the user equipment UE600 includes a processor 601 and a memory 602. The processor 601 may include, for example, a microprocessor, a microcontroller, an embedded processor, or the like. The memory 602 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 602 has stored thereon program instructions. The instructions, when executed by the processor 601, may perform the above-described method performed by the user equipment as detailed in the present disclosure.

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 conditional handover method performed by a user equipment, comprising the steps of:

a condition switching monitoring step, in which User Equipment (UE) receives a Radio Resource Control (RRC) message containing a condition switching command from a source base station, stores condition switching configuration in the condition switching command, and monitors whether the switching condition is met according to the switching condition;

A conditional switch execution step, when the UE monitors that the switch condition in the stored conditional switch configuration is satisfied, the conditional switch is initiated;

an RRC message receiving step, wherein the UE which is executing the condition switching receives RRC message from the source base station;

a conditional switch stopping step in which the UE stops an ongoing conditional switch process;

and executing RRC configuration, wherein the UE executes corresponding configuration according to the configuration in the RRC message received in the ongoing conditional switching process.

2. The conditional handover method performed by a user equipment according to claim 1,

the RRC message from the source base station received by the UE performing the conditional handover includes the following cases:

case 1: the RRC message comprises a handover command;

case 2: the RRC message comprises configuration information for conditional handover, and the configuration information for conditional handover comprises indication information for releasing a target cell of a handover process currently performed by the UE;

case 3: the RRC message comprises configuration information for conditional handover, and the configuration information for conditional handover comprises modification information related to a target cell of a handover process currently performed by the UE;

Case 4: the RRC message comprises configuration information for conditional switching, and the configuration information for conditional switching comprises information for instructing the UE to release the stored conditional switching command configuration;

case 5: the RRC message comprises configuration information for conditional handover, and the configuration information for conditional handover comprises configuration information of other conditional handover alternative cells which are irrelevant to or different from a target cell of a handover process currently performed by the UE;

case 6: the RRC message contains configuration information that is not used for handover and conditional handover.

3. The conditional handover method performed by a user equipment according to claim 2,

the performing the RRC configuration step is performed after the performing the RRC configuration step or the performing the RRC configuration step is performed after the performing the RRC configuration step.

4. The conditional handover method performed by a user equipment according to claim 3,

in case 3, the performing the RRC configuration step is performed after performing the RRC message receiving step, and includes:

the UE suspends the current ongoing conditional switching process;

determining whether a handover condition of a reconfiguration associated with the target cell associated with the ongoing conditional handover in the conditional handover configuration in the received RRC message is still met.

5. The conditional handover method performed by a user equipment according to claim 4,

and when determining that the switching condition of the reconfiguration associated with the target cell associated with the ongoing conditional switching in the conditional switching configuration in the received RRC message is still satisfied, the UE continues the ongoing conditional switching, otherwise, the UE executes the conditional switching stopping step to stop the ongoing conditional switching process.

6. The conditional handover method performed by a user equipment according to claim 1 or 2,

in the conditional handover stop step, the UE performs one or more of the following operations to stop the ongoing conditional handover procedure:

operation 1: stopping the timer or considering the timer to be overtime;

operation 2: stopping the ongoing random access procedure;

operation 3: canceling the sending of the RRC reconfiguration complete message in the conditional switching execution step;

and operation 4: releasing the RRC entity associated with the target cell;

operation 5: generating failure report information, and including the failure report information in a response message sent to a source base station or a response message sent to a target base station;

operation 6: the conditional switch process is considered to be over.

7. A conditional handover method performed by a user equipment, comprising the steps of:

an RRC message receiving step, wherein the UE which is executing the condition switching receives the RRC message from the source base station;

and the conditional switching continues to execute the step, and the UE does not apply or execute the RRC message received in the ongoing conditional switching process to continue the ongoing conditional switching process.

8. The conditional handover method performed by a user equipment according to claim 7,

in the conditional handover continuation step, the UE performs one or more of the following methods without applying or performing the RRC message received in the ongoing conditional handover procedure to continue the ongoing conditional handover procedure:

when receiving the RRC message from the source base station, the RRC layer ignores or discards the received RRC message;

When the MAC layer receives a logical channel identification indicating that the MAC protocol data unit PDU or the service data unit SDU corresponds to the dedicated control channel DCCH, the MAC layer discards the MAC PDU or the MAC SDU.

9. The conditional handover method performed by a user equipment according to claim 1 or 7,

the conditional handover configuration and the handover condition are associated with a target cell.

10. A user equipment, comprising:

a processor; and

a memory having instructions stored thereon;

the instructions, when executed by the processor, cause the user equipment to perform the method of any of claims 1-9.