CN111866965B

CN111866965B - Conditional switching method and corresponding user equipment

Info

Publication number: CN111866965B
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: 2023-11-17
Anticipated expiration: 2039-04-28
Also published as: WO2020221193A1; CN111866965A

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 the condition switching configuration in the condition switching command, and monitors whether the switching condition is met or not according to the switching condition; a condition switching execution step of initiating condition switching when the UE monitors that the switching condition in the stored condition switching configuration is satisfied; an RRC message receiving step in which the UE performing the conditional handover receives an RRC message from the source base station; a conditional handover stopping step in which the UE stops an ongoing conditional handover procedure; and executing the RRC configuration step, wherein the UE executes corresponding configuration according to the configuration in the RRC message received in the ongoing conditional handover process.

Description

Conditional switching method and corresponding user equipment

Technical Field

The present disclosure relates to the field of wireless communication technologies, and more particularly, to a conditional switching method and a corresponding user equipment.

Background

In month 6 of 2018, a New research project of 5G technical standard was approved at third generation partnership project (3rd Generation Partnership Project:3GPP) RAN#80 (see non-patent document: RP-181433:New WID on NR (New Radio) mobility enhancements). Furthermore, there is another new study item of Release 16 (see non-patent document: RP-190272:WID for Even further Mobility enhancement in E-UTRAN (improved-Universal Terrestrail Radio Access Network)). One of the two projects is to find one of the requirements for mobility in the network: seamless handover, i.e. a handover interruption time of 0 ms or close to 0 ms can be met during cell handover, and the robustness of the handover is enhanced. Among the solutions being investigated to reduce HandOver interruption time and/or to enhance HandOver robustness, there is a solution called Conditional HandOver (CHO). In the CHO mechanism, the base station issues a handover command to the UE in advance, where the handover command includes the condition configuration information. And the UE executes 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 through the advanced issuing of the switching command, so that the switching success rate is improved, and the time delay caused by the switching failure to the service interruption due to the switching command receiving failure is avoided.

The present disclosure addresses some of the problems of implementing CHO in NR and LTE (Long Term Evolution) systems.

Disclosure of Invention

An object of embodiments of the present disclosure is to propose a solution to the problem of implementing CHO technology in NR and LTE systems. More specifically, the present disclosure proposes a solution to the problem of how a UE handles the reception of RRC messages from a source cell in the course 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 presented, 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 the condition switching configuration in the condition switching command, and monitors whether the switching condition is met or not according to the switching condition; a condition switching execution step of initiating condition switching when the UE monitors that the switching condition in the stored condition switching configuration is satisfied; an RRC message receiving step in which the UE performing the conditional handover receives an RRC message from the source base station; a conditional handover stopping step in which the UE stops an ongoing conditional handover procedure; and executing the RRC configuration step, wherein the UE executes corresponding configuration according to the configuration in the RRC message received in the ongoing conditional handover process.

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

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

In the above-described conditional access method performed by the ue, it is preferable that, in case 3, the performing RRC configuration step is performed after the performing the RRC message receiving step, including: the UE suspends the currently ongoing conditional handover procedure; it is determined whether a handover condition for a reconfiguration associated with a target cell associated with an ongoing conditional handover is still met in a conditional handover configuration in the received RRC message.

In the above-described conditional handover method performed by the UE, it is preferable that the UE continues the currently ongoing conditional handover when it is determined that a handover condition for a reconfiguration associated with a target cell associated with the ongoing conditional handover is still satisfied in the conditional handover configuration in the received RRC message, and otherwise, the UE performs the conditional handover stop step to stop the ongoing conditional handover procedure.

In the above-described conditional handover method performed by the user equipment, it is preferable that, in the conditional handover stopping 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 that the timer is overtime; operation 2: stopping the ongoing random access procedure; operation 3: canceling the sending of the RRC reconfiguration completion message in the conditional handover execution step; 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 switching process is considered to end.

According to a second aspect of the present disclosure, a conditional handover method performed by a user equipment is presented, 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 the condition switching configuration in the condition switching command, and monitors whether the switching condition is met or not according to the switching condition; a condition switching execution step of initiating condition switching when the UE monitors that the switching condition in the stored condition switching configuration is satisfied; an RRC message receiving step in which the UE performing the conditional handover receives an RRC message from the source base station; the conditional handover continues with the step that the UE does not apply or perform the RRC message received in the ongoing conditional handover procedure to continue the ongoing conditional handover procedure.

In the above-described 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: the RRC layer ignores or discards the received RRC message when receiving the RRC message from the source base station; when the medium access control MAC layer receives a logical channel identification indicating that a MAC protocol data unit PDU or a service data unit SDU corresponds to a dedicated control channel DCCH, the MAC layer discards the MAC PDU or the MAC SDU.

In the above-described 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, there is provided 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 conditional handover method described above.

According to the conditional switching method executed by the user equipment and the corresponding user equipment, when the UE has initiated the conditional switching process of accessing to the target base station and receives the RRC configuration message from the source base station, time delay and signaling cost caused by incorrect switching or switching failure can be avoided, and the mobile performance of the system can be optimized. In other words, the data interruption delay of "0ms" can be satisfied as much as possible in the mobile handover process, and the robustness of the handover is improved to reach the mobility requirement of 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 schematic block diagram 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 present 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 present disclosure.

In the present disclosure, the terms "include" and "comprise," along with their derivatives, are intended to be inclusive, rather than limiting; the term "or" is inclusive, meaning and/or.

In this specification, the various embodiments described below for the purpose of describing the principles of the present disclosure are illustrative only and should not be construed in any way as limiting 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 defined by the claims and their equivalents. The following description includes numerous specific details to aid in understanding, but these details should be construed as exemplary 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. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness. Furthermore, the same reference numerals are used for similar functions and operations throughout the drawings.

Various embodiments in accordance with the present disclosure are described in detail below with a long term evolution system (Long Term Evolution, LTE)/NR mobile communication system and its subsequent evolutions as an example application environment. However, it should be noted that the present disclosure is not limited to the following embodiments, but is applicable to still other wireless communication systems. Unless specifically stated otherwise, in the present disclosure, concepts of cells and base stations may be interchanged; the LTE system is also used to refer to 5G and later LTE systems (e.g., LTE systems called or connectable to a 5G core network), while LTE may be replaced with E-UTRAN or evolved universal terrestrial radio access (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 (bearm), a source transmission point (Transmission point, TRP), and a target cell may also be referred to as a target base station, a target beam, a target transmission point. The source cell refers to a base station serving the UE, i.e., a base station transmitting an RRC message including a handover command to the UE, connected before the handover procedure is initiated. The target cell refers to a base station connected to the UE for serving the UE 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 (reconfigurationwisync) information element. In the LTE system is an RRC connection reconfiguration message containing a mobile control information (mobility control information) information element. The synchronization reconfiguration information element or the movement control information element contains configuration information of the target base station, such as target cell identification, target cell frequency, common configuration of the target cell, such as system information, random access configuration used by the UE accessing the target cell, security parameter configuration of the UE in the target cell, 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 identical in the present disclosure; similarly, the response message RRC reconfiguration complete message is identical to the RRC connection reconfiguration complete message. The handover command is identical to the RRC message containing the handover command, and refers to an RRC message or configuration in the RRC message that triggers the UE to perform handover. The handover configuration refers to all or part of the configuration in the handover command. Cancel, release, delete, empty, clear, etc. may be replaced. Execution, use, and application alternatives. Configuration and reconfiguration may be replaced. The conditional switch command and the conditional switch configuration may be replaced. Monitoring (monitor) and detection (detect) may be substituted.

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

First, a general handover procedure in an LTE/NR system will be briefly described. The mobility of the connected user is mainly achieved through a handover procedure, that is, a procedure in which the UE in the RRC connected state changes the serving cell. The flow is described briefly below with reference to FIG. 1:

stage 1: and (3) a measuring stage. The base station transmits measurement configuration to User Equipment (UE); and the UE measures the wireless links corresponding to the serving cell or the adjacent cells based on the measurement configuration, and when the configured measurement report condition is met, the UE sends a measurement report to the base station. The measurement phase is not necessary and the UE may be handed off blindly also when the base station has no valid measurement reports.

Stage 2: and a switching preparation stage. The base station determines whether to trigger a handover for the UE in conjunction with the received measurement report and other factors such as the base station load. If the trigger for the UE is determined, the source base station initiates a handover preparation procedure by sending a handover request message to the target base station. The target base station decides whether to accept the current switching request to the UE according to the context of the UE in the switching request message and the available resources of the target base station, if so, the target base station replies a switching confirmation message to the source base station, wherein the switching confirmation message comprises an inter-base station (inter-node) RRC message, namely a switching command.

Stage 3: and switching an execution stage. The source base station issues a handover command to the UE and starts forwarding data of the UE to the target base station. The UE receiving the switching command immediately applies the configuration of the switching command to execute switching, 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.

Stage 4: 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 may release the UE context stored thereon accordingly.

As can be seen from the above, the handover procedure in the current system may cause interruption of data transmission, and in LTE system of Release 14 version, optimization of the handover procedure, such as handover without random access procedure, connection before disconnection (Make Before Break, MBB) and the like, aims to reduce data interruption time in the handover procedure.

Next, a condition-based handover will be briefly described. As described above, in Release 16 technology requirements, it is required to meet the data interruption delay of "0ms" as much as possible during mobile handover, and to improve the robustness of handover to achieve the mobility requirement of seamless handover in NR. In the current switching process, one reason for the interruption of the long-time data transmission caused by the switching failure is the failure of receiving the switching command caused by untimely issuing of the switching command. One possible approach to this problem is a conditional based handover (conditional handover for short). In the condition switching, a relatively conservative measurement report threshold is set, so that a base station can acquire a measurement result in advance, and switching preparation is executed in advance according to the measurement result and a selected target base station, so that the base station can issue a switching command to the UE in advance before a real switching condition (relative to the conservative measurement report threshold) is met, wherein the switching executing condition is carried. Unlike the existing handover mechanism of LTE, after receiving a handover command, the UE does not immediately perform handover, but saves 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. Only when the configured switching condition is detected to be met, the UE starts to execute the stored switching command and accesses the target cell. The above-described switching mechanism is referred to as conditional switching in the present disclosure, but the naming thereof is not limited, and may be referred to as a switching mechanism of an early switching command, an early switching preparation, or the like.

One conclusion is reached on the 3gpp RAN2 working group conference for conditional handover: the RRC connection of the UE is maintained by the source cell after the UE initiates the conditional handover before successfully sending an RRC reconfiguration complete message to the target base station. In other words, the UE still maintains the RRC connection with the source base station until the RRC reconfiguration complete message is successfully transmitted to the target base station. In conditional handover, when to initiate the handover execution phase is determined by the UE, the source base station serving the UE cannot know in time, which may occur when the UE has initiated the conditional handover procedure to the target base station but has received the RRC configuration message from the source base station. The present disclosure proposes the following implementation method for how the UE operates in this case, so that the UE can process the received RRC message in this case, thereby avoiding delay and signaling overhead caused by incorrect handover or handover failure, and optimizing the mobility performance of the system. The UE receives the RRC configuration message from the source base station when there is an ongoing conditional handover procedure (i.e., before the RRC reconfiguration complete message is successfully sent to the target base station, when T304 is in an operating state) including, but not limited to, the following cases:

Case 1: the RRC message includes a handover command. The handover command is a conventional handover command, i.e. a handover command not used 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 in which the UE is currently performing. In other words, the target cell of the conditional handover procedure 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 procedure currently being performed by the UE is one of a plurality of conditional handover alternatives in the RRC message indicating a conditional handover configuration to release.

Case 3: the RRC message includes configuration information for the conditional handover, and the configuration information for the conditional handover includes modification information related to a target cell of a handover procedure in which the UE is currently performing, 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 for instructing the UE to release the stored 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 the target cell of the handover procedure 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 includes configuration information that is not used for handover and conditional handover. Such as the RRC message is not RRC reconfiguration information or the RRC message is RRC reconfiguration information that does not contain a synchronization reconfiguration information element or a mobility control information element. That is, the RRC message is not used for handover, such as for configuration of an additional modification of a secondary cell, etc.

The conditional handover alternative 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 may simultaneously configure one or more handover condition candidate cells for the UE.

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

Example 1

In this embodiment, when the UE performing the conditional handover receives the RRC message from the source base station, the UE stops the ongoing conditional handover procedure, applies or performs the received RRC message. Wherein the conditional switch is being performed may also be described as initiating the conditional switch. The process is described below with reference to fig. 2 and 3.

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

The initiation of the conditional handover is initiated when the UE monitors that the handover condition in the saved conditional handover configuration is met. The conditional handover configuration and the handover condition are associated with a target cell. Preferably, the operation of initiating a conditional switch comprises one or more of: starting a timer T304; executing target cell RRC configuration in the conditional 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 RRC reconfiguration complete message to a lower layer for transmission.

In one embodiment, the UE maintains two sets of access layer protocol stacks (user plane protocol stack or control plane protocol stack) for both the source cell and the target cell during the handover procedure. 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 (Service Data Adaptation Protocol, SDAP) entity or a packet data convergence protocol (Packet Data Covergence Protocol, PDCP) entity or a radio link control (Radio Link Control, RLC) entity or a medium access control (Medium Access Control, MAC) entity. One or more of the operations of the UE initiating the conditional handover are performed in an RRC entity associated with the target cell, for example, the operations of generating an 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 performing random access to the target cell is performed in a MAC entity associated with the target cell.

Step S302: the UE performing the conditional handover receives an RRC message from the source base station (RRC message reception 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 timeout.

Operation 2: stopping the ongoing random access procedure. Alternatively, 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 canceled. Preferably, the sending of the RRC reconfiguration complete canceling message is implemented by reconstructing or releasing the L2 entity corresponding to 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.

Operation 4: 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: a failure report message is generated and included in the response message sent to the source base station (e.g., in case 2-6) or in the response message sent to the target base station (e.g., in case 1). The failure report information includes indication information of the ongoing conditional switching process of the UE, a measurement result which is currently effective by the UE, and the like. The indication information indicating that the UE has an ongoing conditional handover procedure includes target cell information (accessed target cell identity or frequency) indicating that the UE has an initiated or ongoing conditional handover procedure when receiving the RRC message in the above step S302 or that the UE has an initiated or ongoing conditional handover procedure when receiving the RRC message in the above step S302.

Operation 6: the conditional switching process is considered to end.

Step S304: the UE performs the 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, step S304 is performed after step S302 in case 3, including the UE suspending the currently ongoing conditional handover procedure; it is determined whether a handover condition for a reconfiguration associated with a target cell associated with an ongoing conditional handover is still met in a conditional handover configuration in the received RRC message. If yes, the UE continues the current condition switching; if not, the UE performs step S303 to stop the ongoing conditional handover procedure. The UE suspending the currently ongoing conditional handover procedure refers to suspending the relevant operations of the handover procedure.

Obviously, this embodiment further includes, before step S301: step S300, the UE receives the RRC message including the conditional handover command from the source base station, saves the conditional handover configuration in the conditional handover command, and monitors whether the handover condition is satisfied according to the handover condition (conditional handover 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 the handover only if the condition is met, applies the handover configuration, the handover condition is included in the conditional handover command. For example, the handover condition is a measurement event, such as the condition is measurement event A3 (neighbor cell to serving cell signal quality exceeds an offset for a period of time). And the adjacent cells correspond to the switched target cells. In general, all measurement events (see section 5.5.4 in 36.331 and 38.331) defined by the current 3GPP standard specification, such as A1-A5, can be included as handover conditions in the conditional handover command.

Example 2

In this embodiment, when the UE performing the conditional handover receives the RRC message from the source base station, the UE continues the ongoing conditional handover procedure without applying or performing the received RRC message. Wherein, the condition switch being performed may also be described as the condition switch being initiated or the timer T304 for the condition switch being running. The process is described below with reference to fig. 4 and 5.

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

Step S502: the UE performing the conditional handover receives an RRC message from the source base station (RRC message reception 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 it receives the RRC message from the source base station. Optionally, when the UE maintains RRC entities for both the source base station and the target base station, the RRC layer is the RRC layer/entity with which the source base station is associated.

In another implementation, the implementation is performed at the MAC layer. When the MAC layer receives a logical channel identifier indicating that the MAC Protocol Data Unit (PDU) or service Data Unit (Service Data Unit, SDU) corresponds to a dedicated control channel (Dedicated Control CHannal, DCCH), the MAC layer discards the MAC PDU or 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 the data packet received on SRB1 to the upper layer after initiating the random access procedure to the target cell or after initiating the conditional handover. Preferably, the MAC layer/entity is a MAC layer/entity associated with the source base station. The information of the MAC entity on the condition switching is known from the RRC layer or the MAC entity associated with the target cell in the double protocol stack. In other words, after the initiation of the conditional handover, an indication is sent by the RRC layer or the MAC entity associated with the target cell to the MAC entity associated with the source cell informing that the conditional handover is in progress or has been 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 (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 the handover only if the condition is met, applying the handover configuration. For example, the handover condition is a measurement event, such as the condition is measurement event A3 (neighbor cell to serving cell signal quality exceeds an offset for a period of time). And the adjacent cells correspond to the switched target cells.

Example 3

The UE in this embodiment does not process RRC messages 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), RRC messages from or to be sent to the source cell are not processed any more.

Step 1: and initiating a conditional switch.

The operation and procedure for initiating the conditional switch are the same as in the previous embodiment, and are not described here.

Step 2: the radio bearer 1 (Signalling Radio Bearer, srb 1) is signaled on hold (suspend). Optionally, the method further comprises the step of reconstructing PDCP or RLC corresponding to the SRB1. Here, RRC refers to RRC, PDCP or RLC associated with a source cell, and PDCP or RLC associated with a source cell.

Step 3: 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 procedure is successful, SRB1 is restored. The recovering SRB1 further comprises 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 sent to the target cell is successfully generated in the procedure, the SRBl associated with the source base station and its associated RRC entity or L2 entity are released.

Example 4

This embodiment presents a method for ending the conditional handover RRC procedure. So that the UE does not process the RRC message from the source base station even if it receives it before the RRC procedure of the conditional handover is ended, so that the ongoing conditional handover procedure is not interrupted. This embodiment is also applicable to handover procedures using a handover mechanism that communicates with both the source cell and the target cell during a handover procedure (which is not a conditional handover procedure and may be referred to in this disclosure as an enhanced pre-disconnection hold connection (enhanced Make Before Break, eMBB) mechanism or a simultaneous connection handover mechanism or a dual connection 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 the handover procedure of an 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 for transmission via SRB 1. The RRC reconfiguration complete message is sent using the new configuration (i.e., the configuration corresponding to the target cell contained in the corresponding handover command).

Step 2: when the transmission (success) of the RRC reconfiguration complete message is confirmed by the lower layer, the RRC procedure is ended, that is, a handover procedure of a handover command RRC message is performed, 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 when an indication that the RRC reconfiguration complete message transmitted from the lower layer has been transmitted (successful) is received.

This embodiment can be expressed as follows, in conjunction with the existing mechanisms and the contents of the 3GPP standard protocols.

Step 1: when the RRC reconfiguration message is received, the configuration in the RRC reconfiguration message is applied.

In the case of conditional handover, since the RRC reconfiguration message containing the conditional handover command is not immediately applied, but is received and stored on the UE in advance, the time when the RRC reconfiguration message is received refers to when the handover condition satisfies the initiation of the conditional handover.

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 RRC reconfiguration complete message is sent using the new configuration (i.e., the configuration contained in the corresponding RRC reconfiguration message). Optionally, the method further comprises the operation of initiating conditional switching.

Step 2: if a synchronous reconfiguration (reconfiguration wisync) information element is included in a special cell configuration (speculcon) information element and the procedure is a conditional handover or eMBB handover procedure, when the lower layer confirms the transmission (success) of the RRC reconfiguration complete message, the RRC procedure is ended, that is, a handover procedure of a handover command RRC message is performed, and the timer T304 is stopped. The case where the lower layer confirms the transmission (success) of the RRC reconfiguration complete message may also be expressed as when an indication that the RRC reconfiguration complete message transmitted from the lower layer has been transmitted (success) is received. 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), the RRC procedure is ended and timer T304 is stopped when the MAC successfully completes one of the random access procedures triggered in step 1 in the RRC procedure.

The above-described "if synchronization reconfiguration information element is included in the special cell configuration information element" corresponds to the NR system. In LTE systems it is equivalent to "when a mobile control information element (mobile control info) is contained in the RRC reconfiguration message or if the MAC indicates that one physical downlink control channel with a UE specific identity (e.g. cell radio network temporary identity C-RNTI) is successfully received when no random access (rach-skip) is configured. Wherein the special cell configuration information element includes configuration parameters of a special cell of a primary cell group (primary cell PCell) or a special cell of a secondary cell group (primary secondary cell PSCell).

Example 5

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

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

Step 2: the same as in step S302 of example 1.

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

In one embodiment, the satisfaction of the condition specifies whether the timer T310 or T312 is running. T310 or T312 is running and meets the condition; t310 or T312 does not satisfy the condition if not running. For the monitoring of radio link failure, see 3GPP protocol specification documents 36.331 or 38.331, T310 or T312 is used.

In another embodiment, whether the condition is met refers to a channel quality measurement, such as reference signal received power RSRP, being below a threshold value. If the channel quality measured value is lower than a threshold value, the condition is considered to be satisfied; a channel quality measurement above a threshold is considered to be unsatisfactory.

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 situation of the target cell when it receives an RRC message from the source cell in the ongoing conditional handover procedure (T304 for conditional handover is running).

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

Step 2: the same as in step S302 of example 1.

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

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. If the measured value of the channel quality is higher than a threshold value, the condition is not met; a channel quality measurement below a threshold is considered to satisfy the condition.

Example 7

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

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

Step 2: the same as in step S302 of example 1.

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 conditional 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 SRB2 as described in the above embodiments in relation to SRB 1. The ongoing conditional handover may be expressed as executing the saved conditional handover configuration, or the executing RRC message/configuration contains the conditional handover indication/information, or the T304 for the conditional handover is running.

In this disclosure, several different embodiments may work cooperatively.

Fig. 6 is a schematic block diagram of a user equipment UE according to the present disclosure. As shown in fig. 6, the user equipment UE600 comprises a processor 601 and a memory 602. The processor 601 may include, for example, a microprocessor, microcontroller, embedded processor, or the like. The memory 602 may include, for example, volatile memory (such as random access memory RAM), a Hard Disk Drive (HDD), non-volatile memory (such as flash memory), or other memory. The memory 602 has stored thereon program instructions. Which, when executed by the processor 601, may perform the above-described methods performed by the user equipment as described in detail in this disclosure.

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

The method of the present disclosure and the apparatus involved have been described above in connection with the preferred embodiments. Those skilled in the art will appreciate that the methods shown above are merely exemplary. The methods of the present disclosure are not limited to the steps and sequences shown above. The base stations and user equipments shown above may comprise further modules, e.g. may also comprise modules that may be developed or developed in the future that may be used for base stations, MMEs, or UEs, etc. The various identifiers shown above are merely exemplary and are not limiting, and the present disclosure is not limited to specific cells as examples of such identifiers. Many variations and modifications may be made by one of ordinary skill 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 for causing 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 store such as a random access memory RAM, a Hard Disk Drive (HDD), a nonvolatile store such as a flash memory, or other memory system.

A program for realizing 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 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 in which a program is stored dynamically at a short time, or any other recording medium readable by a computer.

The various features or functional modules of the apparatus used in the embodiments described above may be implemented or performed by circuitry (e.g., single-chip or multi-chip integrated circuits). Circuits 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 technologies are presented as an alternative to existing integrated circuits due to advances in semiconductor technology, one or more embodiments of the present disclosure may also be implemented using these new integrated circuit technologies.

Further, the present disclosure is not limited to the above-described embodiments. Although various examples of the embodiments have been described, the present disclosure is not limited thereto. 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, etc.

As above, the embodiments of the present disclosure have been described in detail with reference to the accompanying drawings. However, the specific structure is not limited to the above-described embodiments, and the present disclosure also includes any design modifications 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 the technical means disclosed in the different embodiments are also included in the technical scope of the present disclosure. Further, the components having the same effects described in the above embodiments may be replaced with 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 the condition switching configuration in the condition switching command, and monitors whether the switching condition is met or not according to the switching condition;

A condition switching execution step of initiating condition switching when the UE monitors that the switching condition in the stored condition switching configuration is satisfied;

an RRC message receiving step in which the UE performing the conditional handover receives an RRC message from the source base station;

a conditional handover stopping step in which the UE stops the ongoing conditional handover procedure by stopping the timer T304 or considering that the timer T304 times out;

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

2. The conditional handoff method performed by the user equipment as set forth in claim 1, wherein,

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

case 1: the RRC message includes a handover command;

case 2: the RRC message comprises configuration information for conditional switching, and the configuration information for conditional switching comprises indication information for releasing a target cell of a switching 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 indicating the UE to release the stored conditional switching command configuration;

case 5: the RRC message comprises configuration information for conditional switching, and the configuration information for conditional switching comprises configuration information of other conditional switching candidate cells which are not related or different from a target cell of a switching process currently performed by the UE;

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

3. The conditional handoff method performed by the user equipment as set forth in claim 2, wherein,

the performing RRC configuration step is performed after the performing the conditional handover stopping step, or the conditional handover stopping step is performed after the performing RRC configuration step is performed.

4. The conditional handoff method performed by the user equipment as set forth in claim 3, wherein,

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

the UE suspends the currently ongoing conditional handover procedure;

it is determined whether a handover condition for a reconfiguration associated with a target cell associated with an ongoing conditional handover is still met in a conditional handover configuration in the received RRC message.

5. The conditional handoff method performed by the user equipment as set forth in claim 4, wherein,

and when the condition switching configuration in the received RRC message is determined that the switching condition of the reconfiguration related to the target cell related to the ongoing condition switching still is met, the UE continues the current ongoing condition switching, otherwise, the UE executes the condition switching stopping step to stop the ongoing condition switching process.

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

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

operation 2: stopping the ongoing random access procedure;

operation 3: canceling the sending of the RRC reconfiguration completion message in the conditional handover execution step;

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 switching process is considered to end.

7. The conditional handover method performed by a user equipment according to any one of claims 1-5, wherein,

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

8. 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 according to any of claims 1-7.