CN110582128B

CN110582128B - RRC connection reestablishment method and terminal

Info

Publication number: CN110582128B
Application number: CN201810850201.9A
Authority: CN
Inventors: 徐海博; 魏珍荣; 金辉; 庄宏成
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2018-06-07
Filing date: 2018-07-28
Publication date: 2021-08-03
Anticipated expiration: 2038-07-28
Also published as: CN110582128A

Abstract

The application provides an RRC connection reestablishment method and a terminal, and the method comprises the following steps: when the first condition is met, the terminal communicates with the first cell through the first connection and simultaneously starts a Radio Resource Control (RRC) connection reestablishment process of the second cell through the second connection; or, when the third condition is satisfied, while communicating with the third cell through the third connection, initiating a radio resource control, RRC, connection reestablishment procedure to the fourth cell through the fourth connection. The first cell is a source cell of the terminal; the second cell is a target cell meeting the event entry condition of a3, the third cell is a target cell in the process of cell handover executed by the terminal, and the fourth cell is a cell selected by the terminal in the process of cell selection executed by the terminal. The method can be suitable for reestablishing RRC connection in a cell switching failure scene so as to quickly recover the terminal service and reduce service interruption time.

Description

RRC connection reestablishment method and terminal

The present application claims priority from the chinese patent application filed on 2018, on month 07, 06, having application number 201810581502.6 and entitled "a method and apparatus for maintaining a communication connection," the entire contents of which are incorporated herein by reference.

Technical Field

The present application relates to the field of wireless communications, and in particular, to an RRC connection reestablishment method and a terminal.

Background

In an existing communication system, such as a Long Term Evolution (LTE) system, a terminal, such as a User Equipment (UE) and a mobile phone, during a process of moving from a current serving cell (hereinafter, referred to as a current cell) to a neighboring cell of the current cell (hereinafter, referred to as a neighboring cell), if the terminal detects that a difference between a signal quality of the neighboring cell and a signal quality of the current cell is greater than a preset quality threshold, and/or a difference between a signal strength of the neighboring cell and a strength of the current cell is greater than a preset strength threshold (i.e., entry conditions of an a3 event are met), the terminal starts a measurement report trigger timer (time to trigger, TTT), and after the TTT is overtime, the terminal reports a measurement report of a source cell and the neighboring cell. Then, the terminal initiates a cell handover process with the current cell as a source cell and the neighboring cell as a target cell according to the received handover command, so as to reestablish Radio Resource Control (RRC) connection between the terminal and the communication system and recover the service before handover. Specifically, the cell handover process may include the following steps: reporting a measurement report to a source cell; receiving a switching command which is received and forwarded by a source cell from a target cell, and starting a switching timer T304; sending a random access preamble to a target cell; and receiving a random access response issued by the target cell.

However, if the cell handover fails, such as any of the above steps, the terminal needs to wait for a period of time before initiating the RRC connection re-establishment procedure on the serving cell selected in the subsequent cell selection procedure. Further, if the RRC connection re-establishment procedure also fails, the terminal needs to enter an idle state to re-initiate the RRC connection establishment procedure, which may result in a service drop. In other words, when the cell handover fails, the time consumed by the terminal to reestablish the RRC connection and recover the service is long, which results in long service interruption time and low efficiency of the terminal.

Currently, some terminals are configured with two sets of independent transceiving devices, such as two sets of independently controllable radio frequency transceiving antennas and a control circuit corresponding to each set of antennas, so as to support Dual Connectivity (DC) of the same or different systems, as if one terminal maintains communication connection with an evolved Node B (eBN) of an LTE system and a gNB of a New Radio (NR) system (also referred to as a 5G system).

Disclosure of Invention

The application provides an RRC connection reestablishment method and a terminal, which aim to reduce service interruption time caused by cell switching failure of the terminal and improve the efficiency of RRC connection reestablishment and service transmission recovery.

The terminal in the embodiments of the present application is a terminal with dual connectivity.

In a first aspect, an RRC connection reestablishment method is provided, including: and when the first condition is met, the terminal communicates with the first cell through the first connection and simultaneously starts a Radio Resource Control (RRC) connection reestablishment process of the second cell through the second connection. The first cell is a source cell of the terminal; the second cell is a target cell satisfying the a3 event entry condition.

The RRC connection reestablishment method provided in the embodiment of the present application enables, in a process of a terminal switching from a source cell to a target cell, when a first condition is met and cell switching fails, while communicating with the source cell (first cell) through one connection (first connection), an RRC connection reestablishment process is initiated to a target cell (second cell) meeting an a3 event entry condition through another connection (second connection), so that a probability that a problem of long service interruption time and even a disconnection caused by the RRC connection reestablishment process can be initiated again after waiting for a period of time under a condition that the first condition is met and cell switching fails can be reduced, thereby reducing a service interruption time and improving RRC connection reestablishment efficiency.

In some embodiments, the first condition may include one of: the entry condition of the a3 event is met and a Radio Link Problem (RLP) occurs in the first cell; the entry condition of the A3 event meets the condition that the terminal is triggered to report the measurement report to the first cell, and the first cell has a radio link problem. The measurement report includes a measurement report of the source cell and/or the target cell, so that the first cell determines whether the terminal meets a preset cell handover condition, such as an S criterion, according to the measurement report.

Illustratively, the entry condition of the above-mentioned a3 event may be at least one of: the difference value between the signal quality of the adjacent cell and the signal quality of the source cell is greater than or equal to a preset quality threshold value; and the difference value between the signal intensity of the adjacent cell and the signal intensity of the source cell is greater than or equal to a preset intensity threshold value. Since the entry condition of the a3 event is prior art, the description of the present application is omitted.

Illustratively, the occurrence of the radio link problem in the first cell means that a traffic connection between the terminal and the first cell has a problem. For example, due to a weak signal and/or strong interference, the error rate of the service and the signaling received by the terminal from the first cell is higher than a preset error rate threshold, the retransmission ratio or the retransmission number of the service data is greater than a preset retransmission threshold, and the like.

In one possible design approach, initiating a radio resource control, RRC, connection reestablishment procedure to the second cell over the second connection may include: and establishing a first Media Access Control (MAC) entity and a first physical layer entity, and configuring the first MAC entity and the first physical layer entity according to the public radio resource configuration information in the system information of the second cell. The first MAC entity and the first physical layer entity are protocol stack entities corresponding to the second connection and/or the second cell, and are mainly used to support the terminal to initiate an RRC connection reestablishment process to the second cell through the second connection, so as to recover the service as soon as possible, reduce the service interruption duration, and improve the user experience.

In a possible design method, the RRC connection reestablishment method provided in the first aspect of the present application may further include: and when the second condition is met, the terminal terminates the RRC connection reestablishment process.

For example, the second condition may be: before receiving the RRC connection reestablishment message sent by the second cell, the terminal determines that the radio link problem occurring in the first cell is recovered, that is, the service connection between the terminal and the communication system is recovered in the first cell, and it is not necessary to continue to perform the RRC connection reestablishment procedure in the second cell.

For example, the second condition may be: the terminal determines that the leaving condition of the a3 event is satisfied before receiving the RRC connection re-establishment message transmitted by the second cell. Wherein, corresponding to the entry condition of the A3 event, the exit condition of the A3 event may be at least one of: the difference value between the signal quality of the adjacent cell and the signal quality of the source cell is smaller than a preset quality threshold value; the difference between the signal strength of the neighboring cell and the signal strength of the source cell is smaller than a preset strength threshold. Since the leaving condition of the a3 event is prior art, the description of the present application is omitted.

For example, the second condition may be: the terminal has received the handover command sent by the first cell before receiving the RRC connection reestablishment message sent by the second cell. The handover command carries configuration information of radio resources allocated to the terminal by the second cell, and is generally used for handing over the terminal to the second cell. In other words, the second cell already allows the terminal to switch to the second cell, and necessary radio resources are allocated to the terminal, and the terminal only needs to directly switch to the second cell according to the radio resources allocated to the terminal, so that it is not necessary to perform a time-consuming and more complicated RRC connection re-establishment procedure, so as to reduce unnecessary signaling interaction between the terminal and the second cell.

In a possible design method, the RRC connection reestablishment method provided in the first aspect of the present application may further include: if the terminal does not receive the handover command until the terminal receives the RRC connection reestablishment message sent by the second cell, the terminal disconnects the first connection after receiving the RRC connection reestablishment message sent by the second cell, that is, in view of the fact that the service connection between the terminal and the communication system has been restored on the second cell, it is not necessary to continue to perform the cell handover procedure for handing over the terminal from the source cell to the second cell, nor to continue to maintain the service connection between the terminal and the first cell. Thus, in order to reduce the signaling interaction between the terminal and the communication system, the terminal may choose to disconnect the first connection.

In some embodiments, the RRC connection reestablishment method provided in the first aspect of the present application may further include: if the terminal does not receive the switching command until the terminal receives the RRC connection reestablishment message sent by the second cell, the terminal releases one or more first Packet Data Convergence Protocol (PDCP) entities, one or more first Radio Link Control (RLC) entities, a second MAC entity and a second physical layer entity corresponding to the first cell and/or the first connection after receiving the RRC connection reestablishment message sent by the second cell, so as to save resources.

In a second aspect, an RRC connection reestablishment method is provided, including: and when the third condition is met, the terminal communicates with the third cell through the third connection and simultaneously starts a Radio Resource Control (RRC) connection reestablishment process of the fourth cell through the fourth connection. The third cell is a target cell in the process of cell switching executed by the terminal, and the fourth cell is a cell selected by the terminal in the process of cell selection executed by the terminal.

In the RRC connection reestablishment method provided in the second aspect of the present application, in a handover process from a source cell to a target cell (a third cell), when a third condition is met and cell handover fails, while communicating with the target cell through one connection (a third connection), an RRC connection reestablishment process is initiated to a cell (a fourth cell) selected by a cell selection process executed by a terminal through another connection (a fourth connection), so as to reduce a probability that a service interruption time is long and even a disconnection problem occurs due to the RRC connection reestablishment process being able to be initiated again after waiting for a certain time under a condition that the third condition is met and cell handover fails, which can reduce a service interruption time and improve RRC connection reestablishment efficiency.

In one possible design method, the third condition may be: after receiving a handover command with a third cell as a target cell, the terminal sends a random access preamble to the third cell for a preset number of times, which means that a random access process initiated by the terminal to the third cell is not successful. In view of this, in order to recover the service between the terminal and the communication system as soon as possible and reduce the service interruption time, in the embodiment of the present application, the terminal may perform the cell selection procedure and the RRC connection re-establishment procedure through the fourth connection. The preset number of transmissions may be equal to or less than the maximum number of transmissions for transmitting the random access preamble specified by the existing protocol, for example, the preset number of transmissions is 50% of the maximum number of transmissions.

In some embodiments, initiating a radio resource control, RRC, connection reestablishment procedure to the fourth cell over the fourth connection may include: and establishing a third Media Access Control (MAC) entity and a third physical layer entity, and configuring the third MAC entity and the third physical layer entity according to the public radio resource configuration information in the system information of the fourth cell. The third MAC entity and the third physical layer entity are protocol stack entities corresponding to the fourth connection and/or the fourth cell, and are mainly used to support the terminal to initiate an RRC connection reestablishment process to the fourth cell through the fourth connection, so as to recover a service as soon as possible, reduce a service interruption duration, and improve user experience.

In some embodiments, the RRC connection reestablishment method provided in the second aspect of the present application may further include: and when the fourth condition is met, the terminal terminates the RRC connection reestablishment process.

Illustratively, the fourth condition may be: before receiving the RRC connection reestablishment message sent by the fourth cell, the terminal successfully completes the random access procedure in the third cell, that is, the service connection between the terminal and the communication system has been restored in the third cell, and it is not necessary to continue to perform the RRC connection reestablishment procedure in the fourth cell.

In a possible design method, the RRC connection reestablishment method provided in the second aspect of the present application may further include: if the terminal does not successfully complete the random access process in the third cell until receiving the RRC connection reestablishment message sent by the fourth cell, the terminal disconnects the connection with the third cell after receiving the RRC connection reestablishment message, that is, the service connection (fourth connection) between the terminal and the communication system has been restored in the fourth cell, and it is not necessary to continue to perform the cell handover process for handing over the terminal from the source cell to the third cell. In view of this, the terminal may choose to disconnect the third connection in order to reduce the signaling interaction between the terminal and the third cell.

In some embodiments, the RRC connection reestablishment method provided in the second aspect of the present application may further include: if the random access process on the third cell is not successfully completed until the RRC connection reestablishment message sent by the fourth cell is received, the terminal releases one or more second packet data convergence protocol PDCP entities, one or more second radio link control RLC entities, a fourth MAC entity and a fourth physical layer entity corresponding to the third cell and/or the third connection after receiving the RRC connection reestablishment message, so as to save resources.

In a third aspect, a communication apparatus is provided, including: the device comprises a processing module, a first communication module and a second communication module. The processing module is configured to, when the first condition is met, initiate a radio resource control RRC connection reestablishment procedure to the second cell through the second connection while communicating with the first cell through the first connection. The first cell is a source cell of the terminal; the second cell is a target cell meeting the A3 event entry condition, and the first communication module is used for establishing a first connection; the second communication module is used for establishing a second connection.

Wherein the first condition may include one of: the entry condition for the a3 event is met and the first cell has a radio link problem. The entry condition of the A3 event meets the condition that the terminal is triggered to report the measurement report to the first cell, and the first cell has a radio link problem.

In one possible design, the processing module is configured to initiate a radio resource control, RRC, connection re-establishment procedure to a second cell over a second connection, and includes: establishing a first Media Access Control (MAC) entity and a first physical layer entity, and configuring the first MAC entity and the first physical layer entity according to public radio resource configuration information in system information of a second cell; wherein the first MAC entity and the first physical layer entity are protocol stack entities corresponding to the second connection and/or the second cell.

In one possible design, the processing module is further configured to terminate the RRC connection reestablishment procedure when the second condition is satisfied. Wherein the second condition may be one of: before the second communication module receives an RRC connection reestablishment message sent by the second cell, the processing module determines that the radio link problem occurring in the first cell is recovered; before the second communication module receives an RRC connection reestablishment message sent by the second cell, the processing module determines that the leaving condition of the A3 event is met; before the second communication module receives an RRC connection reestablishment message sent by a second cell, the first communication module receives a switching command sent by a first cell; and the switching command is used for switching the terminal to the second cell.

In a possible design, the processing module is further configured to disconnect the first connection after the second communication module receives the RRC connection reestablishment message sent by the second cell if the first communication module does not receive the handover command until the second communication module receives the RRC connection reestablishment message sent by the second cell.

In a possible design, the processing module is further configured to, if the first communication module does not receive the handover command until the second communication module receives the RRC connection reestablishment message sent by the second cell, release one or more first packet data convergence protocol PDCP entities, one or more first radio link control RLC entities, the second MAC entity, and the second physical layer entity corresponding to the first cell and/or the first connection after the second communication module receives the RRC connection reestablishment message sent by the second cell.

In a fourth aspect, a communication apparatus is provided, including: the device comprises a processing module, a third communication module and a fourth communication module. And the processing module is configured to, when the third condition is met, initiate a radio resource control RRC connection reestablishment procedure to the fourth cell through the fourth connection while communicating with the third cell through the third connection. The third cell is a target cell in the process that the terminal executes cell switching, the fourth cell is a cell selected by the terminal in the process that the terminal executes cell selection, and the third communication module is used for establishing third connection; and the fourth communication module is used for establishing a fourth connection.

Wherein, the third condition may be: after the third communication module receives a handover command with the third cell as a target cell, the number of times that the third communication module sends the random access preamble to the third cell reaches a preset sending number.

In one possible design, the processing module is configured to initiate a radio resource control, RRC, connection re-establishment procedure to a fourth cell over a fourth connection, and includes: the processing module is used for establishing a third Media Access Control (MAC) entity and a third physical layer entity, and configuring the third MAC entity and the third physical layer entity according to public wireless resource configuration information in system information of a fourth cell. Wherein the third MAC entity and the third physical layer entity are protocol stack entities corresponding to the fourth connection and/or to the fourth cell.

In one possible design, the processing module is further configured to terminate the RRC connection reestablishment procedure when a fourth condition is met. Wherein the fourth condition is: and before the fourth communication module receives the RRC connection reestablishment message sent by the fourth cell, the random access process of the communication device on the third cell is successfully completed.

In a possible design, the processing module is further configured to disconnect the third connection after the fourth communication module receives the RRC connection reestablishment message if the communication apparatus does not successfully complete the random access procedure in the third cell until the fourth communication module receives the RRC connection reestablishment message sent by the fourth cell.

In a possible design, the processing module is further configured to release one or more second packet data convergence protocol PDCP entities, one or more second radio link control RLC entities, a fourth MAC entity, and a fourth physical layer entity corresponding to the third cell and/or the third connection after the fourth communication module receives the RRC connection reestablishment message if the communication apparatus does not successfully complete the random access procedure on the third cell until the fourth communication module receives the RRC connection reestablishment message sent by the fourth cell.

In a fifth aspect, a communication device is provided for performing the RRC connection reestablishment method according to the first aspect or any of the possible implementation manners of the first aspect, and/or the RRC connection reestablishment method according to the second aspect or any of the possible implementation manners of the second aspect.

In a sixth aspect, a communication apparatus is provided, including: a processing module and a communication module, wherein the processing module is configured to perform the RRC connection reestablishment method according to any one of the possible implementations of the first aspect or the first aspect, and/or the RRC connection reestablishment method according to any one of the possible implementations of the second aspect or the second aspect.

In one possible design, the communication device may further include a storage module; the storage module is configured to store instructions, and the processing module is configured to execute the instructions stored by the storage module, so that the processing module performs the RRC connection reestablishment method according to any one of the possible implementations of the first aspect or the first aspect, and/or the RRC connection reestablishment method according to any one of the possible implementations of the second aspect or the second aspect.

In some embodiments, the communication device may be a chip or a system of chips.

In a seventh aspect, a terminal is provided, including: a processor coupled with the memory. Wherein the memory is used for storing the computer program; a processor configured to execute a computer program stored in a memory, so as to enable a terminal to perform the RRC connection reestablishment method according to any one of the possible implementations of the first aspect or the first aspect, and/or the RRC connection reestablishment method according to any one of the possible implementations of the second aspect or the second aspect.

In an eighth aspect, there is provided a computer program product comprising: computer program code for performing, when the computer program code runs on a computer, the RRC connection re-establishment method according to any one of the first aspect or any one of the possible implementations of the first aspect, and/or the RRC connection re-establishment method according to any one of the second aspect or any one of the possible implementations of the second aspect.

In a ninth aspect, there is provided a readable storage medium comprising a program or instructions which, when executed on a computer, performs the RRC connection reestablishment method according to any one of the possible implementations of the first aspect or the first aspect, and/or the RRC connection reestablishment method according to any one of the possible implementations of the second aspect or the second aspect.

By the RRC connection reestablishment method provided by the embodiment of the application, the method for quickly reestablishing the RRC connection to recover the terminal service in a cell switching failure scene can be provided.

Drawings

Fig. 1 shows a schematic diagram of a communication system suitable for use in the communication method of the embodiments of the present application;

FIG. 2 is an interaction flowchart of a conventional RRC connection reestablishment method in a handover failure scenario;

fig. 3 is a schematic flowchart of a RRC connection reestablishment method according to a first embodiment of the present disclosure;

fig. 4A is a first scenario diagram illustrating a first RRC connection reestablishment method according to an embodiment of the present disclosure;

fig. 4B is a schematic view of a scenario in which the RRC connection reestablishment method one provided in the embodiment of the present application is applied;

fig. 4C is a schematic view of a scenario in which the RRC connection reestablishment method one provided in the embodiment of the present application is applied;

fig. 4D is a schematic view of a scenario applicable to the RRC connection reestablishment method one according to the embodiment of the present application;

fig. 5A is a schematic view of a scenario in which a RRC connection reestablishment method according to the first embodiment of the present application is applied;

fig. 5B is a schematic view illustrating a scene six to which the RRC connection reestablishment method according to the first embodiment of the present application is applied;

fig. 5C is a schematic view illustrating a scenario in which the RRC connection reestablishment method according to the first embodiment of the present application is applied;

fig. 5D is a schematic view eight of a scenario in which the RRC connection reestablishment method according to the first embodiment of the present application is applied;

fig. 6 is a schematic view illustrating a scenario in which a RRC connection reestablishment method according to a first embodiment of the present application is applied;

fig. 7 is a schematic flowchart of a RRC connection reestablishment method two according to the embodiment of the present application;

fig. 8 is a first scenario diagram illustrating an RRC connection reestablishment method according to a second embodiment of the present disclosure;

fig. 9 is a schematic view of a second scenario in which the RRC connection reestablishment method provided in the embodiment of the present application is applied;

fig. 10 is a schematic structural diagram of a communication device according to an embodiment of the present application;

fig. 11 is a schematic structural diagram of another communication device according to an embodiment of the present application;

fig. 12 is a schematic structural diagram of a terminal according to an embodiment of the present application.

Detailed Description

The RRC connection reestablishment method and the terminal provided in the embodiments of the present application are described in detail below with reference to the accompanying drawings.

The embodiment of the application can be applied to a Time Division Duplexing (TDD) scene and a Frequency Division Duplexing (FDD) scene.

The RRC connection reestablishment method provided in the embodiment of the present application may be applied to the communication system shown in fig. 1, where the communication system may be a communication system that supports at least one of the following systems: an LTE system, a Worldwide Interoperability for Microwave Access (WiMAX) system, a fifth Generation (5G) system, such as a New Radio (NR) system, and a future communication system, such as a 6G system.

As shown in fig. 1, the communication system may include: a terminal and a network device. The terminal in fig. 1 is a terminal with Dual Connectivity (DC) capability, and is mainly used to connect to at least one network device deployed by an operator through an air interface, so as to receive a network service; a terminal with dual connectivity capability needs to have two sets of transceivers, or two sets of transceiver chains, installed. The network device is mainly used for realizing functions of a wireless protocol stack, resource scheduling and wireless resource management, wireless access control and mobility management.

The dual connectivity may be that the terminal communicates with network devices of different systems at the same time, or that the terminal communicates with different network devices of the same system at the same time, or that the terminal communicates with different cells of the same network device at the same time, which is not limited in the embodiment of the present application.

For example, in the first stage of 5th generation (5G) system deployment, a non-independent networking mode of 5G NR, that is, an E-UTRAN NR dual connectivity (EN-DC) networking, is often selected. Assuming that in a communication system deployed in an EN-DC manner, the network device 102 is an eNB in an LTE system, the network device 104 is a gNB in an NR system, and the terminal 106 can communicate with the eNB and the gNB, respectively. For another example, both network device 102 and network device 104 are a gNB in an NR system, and terminal 106 may communicate with both gnbs at the same time. For another example, the network device 102 and the network device 104 may also be deployed co-sited, that is, the network device 102 and the network device 104 are the same base station, the base station may include at least two cells, and the dual connectivity may also be that the terminal 106 communicates with two cells of the base station at the same time. Of course, in the case of co-sited deployment, the at least two cells may be cells supporting the same system, or cells supporting different systems, and the embodiment of the present application is not limited.

The terminal may also be referred to as a User Equipment (UE), an access terminal, a subscriber unit, a subscriber station, a mobile station, a remote terminal, a mobile device, a user terminal, a wireless communication device, a user agent, or a user equipment. The terminal in the embodiment of the present application may be a mobile phone (mobile phone), a tablet computer (Pad), a computer with a wireless transceiving function, a Virtual Reality (VR) terminal, an Augmented Reality (AR) terminal, a wireless terminal in industrial control (industrial control), a wireless terminal in self driving (self driving), a wireless terminal in remote medical treatment (remote medical), a wireless terminal in smart grid (smart grid), a wireless terminal in transportation safety (transportation safety), a wireless terminal in smart city (smart city), a wireless terminal in smart home (smart home), and the like. The embodiments of the present application do not limit the application scenarios. The terminal and the chip that can be disposed on the terminal are collectively referred to as a terminal in this application.

The network device may be an access network device such as a base station, such as a Node B (NB) in a 3rd generation (3G) mobile communication system, an evolved node B (eNB) in an LTE system, a gNB in an NR system, and the like.

It should be noted that fig. 1 is only an exemplary architecture diagram, and the network architecture may include other functional units besides the functional units shown in fig. 1, which is not limited in this application.

When the terminal moves from one cell (current serving cell), such as a cell included in network device 102, to another cell (neighboring cell), such as a cell included in network device 104, the signal strength and/or signal quality of the two cells received by the terminal may change. As shown in fig. 2, in the prior art, when the entry condition of the a3 event is satisfied, the terminal may perform a cell handover procedure with the current cell as a source cell and the neighboring cell as a target cell as shown in fig. 2 under the control of the network device.

As shown in fig. 2, the cell handover procedure may include S201 to S210:

s201, the terminal detects that the entering condition of the A3 event is met.

Wherein, the entry condition of the a3 event may be: the difference between the signal strength of the adjacent cell received by the terminal and the signal strength of the current cell received by the terminal is greater than or equal to a preset strength threshold, and/or the difference between the signal quality of the adjacent cell received by the terminal and the signal quality of the current cell received by the terminal is greater than or equal to a preset quality threshold. Since the entry condition of the a3 event is prior art, the embodiment of the present application is not described in detail.

However, when the terminal detects that the entry condition of the a3 event is satisfied, the terminal first starts a Time To Trigger (TTT) timer, and when the TTT times out, the terminal reports the measurement report. In other words, even if the entry condition of the a3 event is satisfied, the terminal does not report the measurement report immediately, but reports the measurement report after waiting for a period of time.

S202, the terminal reports the measurement report to the source cell.

The measurement report carries the received signal strengths of the source cell and the neighboring cell, and/or the received signal qualities of the source cell and the neighboring cell. For example, the terminal may report the measurement report through an air interface between the terminal and the source cell.

Thereafter, in the process of S202, if the Radio Link Problem (RLP) is detected in the source cell, the terminal starts a timer T310, and tries to receive a handover command described in S206 below during the operation of T310. Among them, in the prior art, when the UE detects N310 consecutive out-of-sync (out-of-sync) situations, it is considered that a radio link problem occurs, and starts T310.

And S203, the source cell determines that the terminal meets the switching condition according to the measurement report.

The handover condition may be determined by a network device, and may be any condition in the prior art, which is not limited in the embodiment of the present application.

S204, the source cell sends a switching request to the target cell.

The handover request carries the identifier of the terminal, current service information, resource allocation requirements, and the like. In particular, the handover request may be transmitted over a wired or wireless interface between the source cell and the target cell. The handover request is transmitted, for example, over an X2 interface between the source cell and the target cell. In view of the fact that the handover request is the prior art, the embodiments of the present application are not described in detail.

And S205, the target cell sends a switching response to the source cell according to the switching request.

And the target cell determines whether to approve the terminal to be switched to the target cell according to the comparison result of the idle resources of the target cell and the resource requirement of the current service of the terminal. And if the terminal agrees to switch, the switching response carries RRC connection reconfiguration information used for the terminal to access the target cell.

And S206, the source cell sends a switching command to the terminal.

The handover command is generated according to the handover response, and carries information of the target cell, such as a cell identifier of the target cell, RRC connection reconfiguration information, and the like. Similar to the reporting of the measurement report by the terminal, the handover command may be transmitted through an air interface between the source cell and the terminal. In view of the fact that the handover command is the prior art, the embodiments of the present application are not described in detail.

It should be noted that, if the terminal detects that a Radio Link Problem (RLP) occurs in the source cell, the terminal starts the timer T310. From the time-out of the TTT, the terminal starts reporting the measurement report for the first time, and if the terminal still does not receive the handover command until the time-out of the T310, the terminal may determine that a Radio Link Failure (RLF) occurs in the source cell. In order to recover the terminal service, the terminal may initiate a cell selection procedure to reselect the serving cell, initiate an RRC connection re-establishment procedure to the selected serving cell, and start a timer T311. Of course, if T311 is already out of time but the RRC connection between the terminal and the communication system cannot be reestablished, the terminal may determine that the RRC connection reestablishment process fails and needs to restart the network searching process.

S207, the terminal disconnects the RRC connection with the source cell according to the switching command.

Specifically, when the terminal receives the handover command, it will disconnect the RRC connection with the source cell, start the timer T304, and initiate a cell handover procedure to the target cell carried by the handover command.

Since the terminal disconnects the RRC connection with the source cell in S207, the service between the terminal and the communication system is already interrupted from S207, and the service interruption state continues until the terminal reestablishes its RRC connection location with the communication system, for example, the current cell handover is successful, or the subsequent RRC connection reestablishment is successful although the current cell handover is failed.

Wherein, the cell switching process comprises: downlink synchronization of the terminal and the target cell, and a random access process. The random access procedure may include S208 described below.

S208, the terminal sends the random access preamble to the target cell.

S209, the target cell sends a random access response to the terminal.

Wherein, the random access preamble is generally used for uplink synchronization of the terminal and the target cell.

In practical applications, the maximum number of transmissions of the random access preamble sent by the terminal to the target cell is usually set, for example, 4 times. If the number of times that the terminal actually sends the random access preamble has reached the maximum number of times, and the terminal still does not receive the random access response sent by the target cell until T304 times out, the terminal may determine that a cell handover failure (HOF) has occurred. In order to recover the service between the terminal and the communication system, after determining that the HOF occurs, the terminal may start a cell selection procedure to reselect a serving cell, initiate an RRC connection re-establishment procedure to the selected serving cell, and start a timer T311. Since the cell selection procedure and the RRC connection re-establishment procedure are prior art, details are not described in the embodiments of the present application.

S210, the terminal reports the RRC connection reconfiguration completing message to the target cell.

Specifically, the terminal completes self-configuration according to the RRC connection reconfiguration information carried by the random access response, and sends an RRC connection reconfiguration complete message to the target cell.

By performing S201-S210, the serving cell of the terminal is handed over from the source cell to the target cell, and then the terminal can continue to receive network services on the target cell, for example, resume the service between the terminal and the source cell before performing the cell handover procedure.

It should be noted that the cell handover process includes many steps, and in the cell handover process, the terminal is located in the edge areas of the source cell and the target cell, the signal quality is poor, the signal strength is low, and strong inter-cell interference often exists, that is, the wireless communication environment where the terminal is located is relatively poor at this time, which may cause the terminal to make an error in the process of executing the above S201-S210, thereby causing the cell handover failure. According to the cause, the cell handover failure may include cell handover failures in the following two scenarios:

scene one: because the source cell has a radio link problem, the terminal fails to report a measurement report successfully (S202), or fails to receive a handover command (S206), the terminal may determine that a radio link failure occurs in the source cell, and subsequent steps in the cell handover process cannot be executed, thereby causing a cell handover failure, that is, the cell handover failure in this scenario is caused by a radio link failure occurring in the source cell, and it can be said that the cell handover failure in scenario one is: a radio link failure type cell handover fails.

Scene two: because the terminal is located in the edge area of the target cell, the wireless communication environment is poor, and the target cell cannot receive the random access preamble sent by the terminal (S208), or the terminal cannot receive the random access response issued by the target cell (S209), i.e. a random access failure occurs, and then the terminal cannot re-establish the RRC connection on the target cell, that is, the cell handover failure in scenario two is caused by the random access failure, and it can be said that the cell handover failure in scenario two is: the random access failure type cell handover fails.

For scenario one, the terminal may not confirm that the radio link failure occurs in the source cell and initiate a cell selection process and an RRC connection reestablishment process until the terminal does not receive the handover command issued by the source cell after the terminal reports the measurement report until T310 times out. Therefore, even if the terminal detects that the radio link problem occurs in the source cell, the terminal does not initiate the cell selection process and the RRC connection reestablishment process in advance, and must wait for the time-out of T310, which is a long waiting time, thereby resulting in low efficiency of RRC connection reestablishment, long service interruption time, and poor user experience.

Similarly, for scenario two, the terminal receives the handover command, sends a random access preamble to the target cell, and starts T304, and if the terminal still fails to receive a random access response issued by the target cell until T304 times out, the terminal cannot finally determine that a handover failure of a random access failure type occurs, and starts a cell selection procedure and an RRC connection reestablishment procedure. Therefore, even if the number of times that the terminal transmits the random access preamble has reached the maximum number of times, the terminal cannot start the cell selection procedure and the RRC connection reestablishment procedure in advance, but must wait for the time T304 to timeout, and the waiting time is long, thereby resulting in low efficiency of reestablishing the RRC connection, long service interruption time, and poor user experience.

It should be noted that the serving cell selected by the terminal in the cell selection process may be a source cell, a target cell, or another cell except for the source cell and the target cell, and this embodiment of the present application is not limited thereto.

The embodiment of the application provides two RRC connection reestablishment methods in cell handover failure, which are respectively applied to the scene one and the scene two, so that the service interruption time of a terminal caused by the cell handover failure is reduced, the RRC connection reestablishment efficiency is improved, and the user experience is improved.

Fig. 3 shows an RRC connection reestablishment method applied to scenario one. As shown in fig. 3, the RRC connection reestablishment method includes S301:

s301, when the first condition is met, the terminal communicates with the first cell through the first connection and simultaneously starts a Radio Resource Control (RRC) connection reestablishment process of the second cell through the second connection.

The first cell is a source cell of the terminal, such as a cell included in the network device 102 shown in fig. 1; the second cell is a target cell satisfying the a3 event entry condition, such as the cell included in the network device 104 shown in fig. 1. It can be understood that the source cell and the target cell may also be different cells included in the same base station, and the embodiment of the present application is not limited thereto.

In some embodiments, the first condition may be: the entry condition for the a3 event is met and the first cell, the source cell, has a radio link problem. If the entry condition of the a3 event is satisfied, the terminal starts a timer TTT. The occurrence of a radio link problem at the source cell by the terminal means that the timer T310 is already running.

Fig. 4A-4B show schematic diagrams of two sub-scenarios at a scene that satisfy a first condition.

Illustratively, as shown in fig. 4A, when the entry condition of the a3 event is satisfied to trigger the terminal to start the timer TTT, the first cell has a radio link problem, i.e., the timer T310 corresponding to the first cell and/or the first connection is running. That is, the first cell has radio link problem, i.e. T310 starts counting before, and the entry condition of the a3 event is satisfied to trigger the terminal to start the timer TTT after. In some embodiments, the first Cell is a Primary serving Cell (Primary serving Cell) of the terminal.

Illustratively, as shown in fig. 4B, when the entry condition of the a3 event is satisfied to trigger the opening of the TTT, the T310 corresponding to the first cell and/or the first connection is not yet opened, but during the operation of the TTT, the terminal detects that a radio link problem occurs in the first cell and starts the T310 corresponding to the first cell and/or the first connection. That is, the first cell has a radio link problem, i.e. T310 starts later, while the entry condition for the a3 event is satisfied before the trigger terminal starts the timer TTT.

It is understood that fig. 4A and 4B are only two examples thereof. In fact, as long as there is a time period in which the two timers TTT and T310 operate together (both have been started and have not timed out), it can be regarded that the first condition is satisfied, and as for the sequence of the starting times of the two timers, the embodiment of the present application is not limited.

In the prior art, a terminal reports a measurement report to a first cell only after a TTT expires, or initiates an RRC connection reestablishment procedure and performs cell selection only after a T310 expires. In this embodiment of the present application, when the terminal detects that the first condition shown in fig. 4A is satisfied, instead of initiating the RRC connection re-establishment procedure to the second cell after waiting for the time-out of T310, when the TTT is started and the T310 is running, the terminal immediately initiates the RRC connection re-establishment procedure to the second cell through the second connection, so that the waiting time can be reduced, and the RRC connection re-establishment efficiency can be improved. Similarly, when the terminal detects that the first condition shown in fig. 4B is satisfied, instead of initiating the RRC connection re-establishment procedure to the second cell after T310 times out, when T310 is started, the terminal immediately initiates the RRC connection re-establishment procedure to the second cell through the second connection in advance, which can also reduce the waiting time, thereby improving the RRC connection re-establishment efficiency.

In some embodiments, the first condition may be: the entry condition of the A3 event meets the condition that the terminal is triggered to report the measurement report to the first cell, and the first cell has a radio link problem. The condition that the entry condition of the A3 event meets the requirement that the terminal reports the measurement report to the first cell means that the entry condition of the A3 event meets the requirement that the terminal starts a timer TTT, and when the TTT is overtime, the terminal is triggered to report the measurement report to the first cell.

Fig. 4C-4D show schematic diagrams of two further sub-scenarios of the scenario with the first condition fulfilled.

Illustratively, as shown in fig. 4C, the first cell has had a radio link problem, i.e. has started the timer T310, before the entry condition of the a3 event satisfies the triggered timer TTT timeout. That is, the first cell has a radio link problem, i.e., T310 starts before and the entry condition for the a3 event expires after the triggered timer TTT expires.

Illustratively, as shown in fig. 4D, the entry condition for the a3 event is satisfied that the triggered timer TTT has timed out before the radio link problem occurs in the first cell and the timer T310 is started. That is, the first cell has a radio link problem, i.e., T310 starts later, while the entry condition for the a3 event meets the triggered timer TTT timeout earlier.

It is understood that fig. 4C and 4D are only two examples thereof. In fact, as long as the timer T310 is running and the terminal reports the measurement report to the first cell at the same time, it may be considered that the first condition is met, and as for the occurrence sequence of the two events (T310 starting and reporting the measurement report), the embodiment of the present application is not limited.

In the prior art, the terminal may initiate an RRC connection reestablishment procedure and perform cell selection only after T310 times out, or may initiate a cell handover procedure only after the terminal receives a handover command. In this embodiment of the present application, when the terminal detects that the first condition shown in fig. 4C is satisfied, it does not wait for T310 to time out any more, but when the terminal reports the measurement report, it immediately initiates an RRC connection reestablishment procedure to the second cell through the second connection, so that the waiting time is reduced, and the RRC connection reestablishment efficiency is improved. Similarly, when the terminal detects that the first condition shown in fig. 4D is satisfied, the terminal does not initiate the cell handover procedure to the second cell until T310 times out, but initiates the RRC connection re-establishment procedure to the second cell through the second connection immediately when T310 is started, which also reduces the waiting time, thereby improving the RRC connection re-establishment efficiency.

It should be noted that the entry condition of the a3 event may be at least one of the following: the difference value between the signal quality of the target cell and the signal quality of the source cell is greater than or equal to a preset quality threshold value; and the difference value between the signal intensity of the target cell and the signal intensity of the source cell is greater than or equal to a preset intensity threshold value. For example, a difference between a Reference Signal Receiving Power (RSRP) of a target cell received by a terminal and an RSRP of a source cell received by the same terminal is greater than a preset RSRP threshold. For another example, the difference between the Reference Signal Receiving Quality (RSRQ) of the target cell received by the terminal and the RSRQ of the source cell received by the same terminal is greater than the preset RSRQ threshold. Since the entry condition of the a3 event is prior art, the embodiment of the present application is not described in detail.

Illustratively, the occurrence of the radio link problem in the first cell means that a radio connection between the terminal and the first cell is in problem, which causes an error rate of a service and/or a signaling received by a receiving party to be higher than a preset error rate threshold, or a retransmission ratio or a retransmission number of service data to be larger than a preset retransmission threshold, and the like.

In one possible design approach, initiating a radio resource control, RRC, connection reestablishment procedure to the second cell over the second connection may include: and establishing a first Media Access Control (MAC) entity and a first physical layer entity, and configuring the first MAC entity and the first physical layer entity according to the public radio resource configuration information in the system information of the second cell.

The first MAC entity and the first physical layer entity are protocol stack entities corresponding to the second connection and/or the second cell, and are mainly used to support the terminal to initiate an RRC connection reestablishment process to the second cell through the second connection, so as to recover the service as soon as possible, reduce the service interruption duration, and improve the user experience.

In a possible design method, the RRC connection reestablishment method shown in fig. 3 may further include: and when the second condition is met, the terminal terminates the RRC connection reestablishment process.

In some embodiments, the second condition may be: before receiving the RRC connection reestablishment message sent by the second cell, the terminal determines that the radio link problem occurring in the first cell has recovered, that is, the terminal detects N311 consecutive synchronizations (in-sync) on the first cell, and it is not necessary to continue to perform the RRC connection reestablishment procedure on the second cell. Therefore, the terminal can select to terminate the RRC connection re-establishment procedure, so as to reduce unnecessary signaling interaction between the terminal and the second cell, save resources, and reduce power consumption.

Fig. 5A shows a schematic diagram of a sub-scenario at a scene that satisfies the second condition. As shown in fig. 5A, when the terminal detects that the radio link problem occurred in the first cell has recovered, the terminal may stop timing T310 corresponding to the first cell and/or the first connection, that is, the terminal has recovered communication on the first cell, and does not need to continue to perform the RRC connection re-establishment procedure on the second cell. Thus, the terminal may terminate its RRC connection re-establishment procedure on the second cell.

In some embodiments, the second condition may be: the terminal determines that the leaving condition of the a3 event is satisfied before receiving the RRC connection re-establishment message transmitted by the second cell. Wherein, corresponding to the entry condition of the A3 event, the exit condition of the A3 event may be at least one of: the difference value between the signal quality of the adjacent cell and the signal quality of the source cell is smaller than a preset quality threshold value; the difference between the signal strength of the neighboring cell and the signal strength of the source cell is smaller than a preset strength threshold. Since the leaving condition of the a3 event is prior art, the embodiment of the present application is not described in detail.

Fig. 5B shows a schematic diagram of another sub-scenario at a scene where the second condition is met. As shown in fig. 5B, when the terminal detects that the second cell satisfies the leaving condition of the a3 event, the terminal may stop the TTT count corresponding to the second cell and/or the second connection, that is, the signal quality of the second cell received by the terminal at this time is degraded, and if the terminal has turned around and moved away from the second cell and moves towards the first cell, it is not necessary to continue to perform the RRC connection re-establishment procedure on the second cell. Therefore, the terminal may also terminate its RRC connection re-establishment procedure on the second cell to reduce unnecessary signaling interaction and reduce power consumption.

In some embodiments, the second condition may be: the terminal has received the handover command sent by the first cell before receiving the RRC connection reestablishment message sent by the second cell. The terminal only needs to perform cell switching according to the switching command, and does not need to perform a more time-consuming and more complicated RRC connection reestablishment process, so as to avoid unnecessary signaling interaction between the terminal and the second cell.

Fig. 5C shows a schematic diagram of yet another seed scenario at a scene where the second condition is met. As shown in fig. 5C, the terminal still does not receive the RRC connection re-establishment message sent by the second cell until the terminal receives the handover command sent by the first cell to instruct the terminal to perform handover. Whereas the reception of the handover command indicates that the terminal has been allowed to perform handover, the terminal may directly access the target cell according to the handover command. Therefore, the terminal may also terminate its RRC connection re-establishment procedure on the second cell to reduce unnecessary signaling interaction and reduce power consumption.

It should be noted that, in the sub-scenarios shown in fig. 5A to 5C, the embodiment of the present application does not need to limit the initiation time of the RRC connection re-establishment procedure. In fact, in the sub-scenarios shown in fig. 5A-5C, the initiation time of the RRC connection reestablishment procedure may be any one of fig. 4A-4D. Exemplarily, in the sub-scenario shown in fig. 5C, the initiation time of the RRC connection reestablishment procedure is the same as that shown in fig. 4B (TTT initiation is before, T310 initiation is after). If the initiation time of the RRC connection reestablishment procedure is changed to the initiation time shown in fig. 4C (before the T310 is started, after the TTT timeout triggers the reporting of the measurement report), the sub-scenario shown in fig. 5C may be changed to the sub-scenario shown in fig. 5D.

It is understood that fig. 5C-5D are just a few examples of satisfying the second condition. In fact, as long as the terminal satisfies any one of the following conditions before receiving the RRC connection reestablishment message sent by the second cell, the terminal may be considered to satisfy the second condition: the terminal detects that the radio link problem occurred in the first cell is recovered, the second cell meets the leaving condition of the A3 event, and the terminal receives the switching command sent by the first cell.

In one possible design method, as shown in fig. 6, the RRC connection reestablishment method shown in fig. 3 may further include: and if the terminal does not receive the switching command until the terminal receives the RRC connection reestablishment message sent by the second cell, the terminal disconnects the first connection after receiving the RRC connection reestablishment message sent by the second cell. In other words, the RRC connection re-establishment on the second cell by the terminal is successful, i.e. the service is restored on the second cell, and the terminal does not need to continue to perform the handover procedure for the terminal to handover from the source cell to the target cell, nor does the terminal need to continue to maintain the service connection (first connection) with the first cell. In view of this, the terminal may disconnect the first connection to reduce unnecessary signaling interaction between the terminal and the first cell and save power consumption.

In fact, for the following two events: if one of the RRC connection re-establishment procedures has been successfully performed, i.e. the service between the terminal and the communication system has been restored, the terminal may choose to terminate the other procedure in order to reduce unnecessary signaling interaction between the terminal and the other cell. For example, if the RRC connection re-establishment procedure of the terminal on the second cell has been successfully performed, the terminal may immediately disconnect the first connection. For another example, if the radio link problem of the terminal on the first cell is recovered, the terminal may immediately terminate the RRC connection re-establishment procedure on the second cell.

In some embodiments, the RRC connection reestablishment method shown in fig. 3 may further include: if the terminal does not receive the switching command until the terminal receives the RRC connection reestablishment message sent by the second cell, the terminal releases one or more first Packet Data Convergence Protocol (PDCP) entities, one or more first Radio Link Control (RLC) entities, a second MAC entity and a second physical layer entity corresponding to the first cell and/or the first connection after receiving the RRC connection reestablishment message sent by the second cell, so as to save resources.

It should be noted that, in the embodiment of the present application, it is not required to limit the execution sequence of releasing the PDCP entity, the RLC entity, the second MAC entity, and the second physical layer entity corresponding to the first cell and disconnecting the first connection. For example, the disconnection operation may be performed first and then the release operation may be performed, the release operation may be performed first and then the disconnection operation may be performed, and the release operation and the disconnection operation may also be performed simultaneously, which is not limited in the embodiment of the present application.

The RRC connection reestablishment method provided in the embodiment of the present application enables, in a process of switching from a source cell to a target cell, when a first condition is met and cell handover fails, while communicating with the source cell (first cell) through one connection (first connection), an RRC connection reestablishment process is initiated to a target cell (second cell) meeting an a3 event entry condition through another connection (second connection), so that a probability that a service interruption time is long and even a disconnection problem occurs due to the RRC connection reestablishment process being able to be initiated again after waiting for a period of time under a condition that the first condition is met and cell handover fails can be reduced, a service interruption time can be reduced, and efficiency of reestablishing an RRC connection can be improved.

Fig. 7 shows an RRC connection reestablishment method suitable for scenario two. As shown in fig. 7, the RRC connection reestablishment method includes S701:

and S701, when the third condition is met, the terminal communicates with the third cell through the third connection and simultaneously starts a Radio Resource Control (RRC) connection reestablishment process of the fourth cell through the fourth connection.

The third cell is a target cell in the process of cell switching executed by the terminal, and the fourth cell is a cell selected when the terminal executes the RRC connection reestablishment process.

It should be noted that the third cell in S701 may be the second cell shown in fig. 3 to 6. And the fourth cell is the cell selected when the terminal executes the RRC connection reestablishment process after the cell switching is failed in the scene two. The cell may be a serving cell (source cell) before handover, or may be another cell except for the source cell and a third cell (target cell), which is not limited in this embodiment of the present application.

In one possible design method, the third condition may be: and after receiving a switching command which takes the third cell as a target cell, the terminal sends the random access preamble to the third cell for the preset sending times.

Fig. 8 is a diagram illustrating a sub-scenario satisfying the third condition in scenario two. As shown in fig. 8, after the terminal receives the handover command for instructing the terminal to handover to the third cell and has established its downlink synchronization with the third cell, the terminal may attempt to establish its uplink synchronization with the third cell, such as sending a random access preamble to the third cell and attempting to receive a random access response sent by the third cell, so as to complete its configuration according to the configuration information carried in the random access response, and resume the service before handover on the third cell. When the number of times that the terminal sends the random access preamble reaches the preset sending number, the terminal continues to try to receive the random access response sent by the third cell through the third connection, simultaneously can execute the cell selection process through the fourth connection, and initiates the RRC connection reestablishment process to the fourth cell selected in the cell selection process through the fourth connection, so as to recover the service between the terminal and the communication system as soon as possible and reduce the service interruption time of the terminal caused by the cell switching failure.

For example, the preset number of transmissions may be equal to or less than the maximum number of transmissions of the random access preamble specified by the existing protocol. For example, if the existing protocol specifies that the maximum number of transmissions is 4, the preset number of transmissions may be any one of 1 to 4.

In the prior art, only when the timer T304 times out, the terminal may determine that the cell handover failure has occurred, and initiate a cell selection procedure and an RRC connection reestablishment procedure. In the embodiment of the present application, when the terminal detects that the third condition shown in fig. 8 is satisfied, the terminal does not wait for time-out of T304, but immediately initiates an RRC connection reestablishment procedure to the fourth cell through the fourth connection, so that the waiting time is reduced, and the RRC connection reestablishment efficiency is improved.

In some embodiments, initiating a radio resource control, RRC, connection reestablishment procedure to the fourth cell over the fourth connection may include: and establishing a third Media Access Control (MAC) entity and a third physical layer entity, and configuring the third MAC entity and the third physical layer entity according to the public radio resource configuration information in the system information of the fourth cell. The third MAC entity and the third physical layer entity are protocol stack entities corresponding to the fourth connection and/or the fourth cell, and are mainly used to support the terminal to initiate an RRC connection reestablishment procedure to the fourth cell through the fourth connection.

In some embodiments, the RRC connection reestablishment method shown in fig. 7 may further include: and when the fourth condition is met, the terminal terminates the RRC connection reestablishment process.

For example, as shown in fig. 9, the fourth condition may be: after the terminal initiates the RRC connection reestablishment procedure to the fourth cell through the fourth connection, and before the terminal receives the RRC connection reestablishment message sent by the fourth cell, the cell handover procedure of the terminal on the third cell is successfully completed, that is, the service between the terminal and the communication system is restored on the third cell. For example, the terminal has received the random access response sent by the third cell, and has completed its own configuration according to the configuration information carried in the random access response, and then has sent an RRC connection reconfiguration complete message to the third cell. Since it is not necessary for the terminal to continue performing the RRC connection reestablishment procedure on the fourth cell, the terminal may choose to terminate the RRC connection reestablishment procedure to reduce unnecessary signaling interaction between the terminal and the fourth cell.

In one possible design method, the RRC connection reestablishment method shown in fig. 7 may further include: if the terminal does not successfully complete the random access process on the third cell until receiving the RRC connection reestablishment message sent by the fourth cell, the terminal disconnects from the third cell after receiving the RRC connection reestablishment message, that is, the terminal has recovered the service between the terminal and the communication system on the fourth cell, and it is not necessary to continue to perform the cell handover process for handing over the terminal from the source cell to the third cell. In view of this, the terminal may choose to disconnect the third connection in order to reduce the signaling interaction between the terminal and the third cell.

In fact, for the cell handover procedure performed by the terminal on the third cell through the third connection and the RRC connection reestablishment procedure initiated by the terminal on the fourth cell through the fourth connection, if one of the procedures has been successfully performed, i.e. the terminal service has been restored, the terminal may choose to terminate the other procedure in order to reduce unnecessary signaling interaction between the terminal and the other cell.

In some embodiments, the RRC connection reestablishment method shown in fig. 7 may further include: if the random access process on the third cell is not successfully completed until the terminal receives the RRC connection reestablishment message sent by the fourth cell, the terminal releases one or more second packet data convergence protocol PDCP entities, one or more second radio link control RLC entities, a fourth MAC entity, and a fourth physical layer entity corresponding to the third cell and/or the third connection after receiving the RRC connection reestablishment message, so as to save resources.

In the RRC connection reestablishment method provided in the embodiment of the present application, in a process of switching from a source cell to a target cell (third cell), when a third condition is met and cell handover fails, while communicating with the target cell through one connection (third connection), an RRC connection reestablishment process is initiated to a serving cell (fourth cell) selected by a terminal to perform a cell selection process through another connection (fourth connection), so as to reduce a probability that a service interruption time is long and even a disconnection problem occurs due to the fact that the terminal can reinitiate the RRC connection reestablishment process after waiting for a certain time under a condition that the third condition is met and cell handover fails, which can reduce a service interruption time and improve efficiency of reestablishing an RRC connection.

It is to be understood that the RRC connection reestablishment method described in fig. 3 or any one of the possible implementations thereof, and the RRC connection reestablishment method described in fig. 7 or any one of the possible implementations thereof may be implemented separately or in combination, and the embodiments of the present application are not limited thereto.

The RRC connection reestablishment method according to the embodiment of the present application is described in detail above with reference to fig. 3 to 9. A communication device capable of performing the RRC connection reestablishment method according to the embodiment of the method of the present application is described in detail below with reference to fig. 10 to 11.

An embodiment of the present application provides a communication apparatus, configured to perform an RRC connection reestablishment method according to any one of possible implementation manners of fig. 3 to fig. 6. As shown in fig. 10, the communication apparatus 1000 includes: a processing module 1001, a first communication module 1002A and a second communication module 1002B. The processing module 1001 is configured to, when a first condition is met, initiate a radio resource control, RRC, connection reestablishment procedure of a second cell through a second connection while communicating with a first cell through a first connection; the first cell is a source cell of the terminal; the second cell is a target cell satisfying the a3 event entry condition. The first communication module 1002A is configured to establish a first connection; the second communication module 1002B is used to establish a second connection.

In one possible design, the processing module 1001 is further configured to initiate a radio resource control, RRC, connection reestablishment procedure to the second cell through the second connection, and includes: establishing a first Media Access Control (MAC) entity and a first physical layer entity, and configuring the first MAC entity and the first physical layer entity according to public radio resource configuration information in system information of a second cell; wherein the first MAC entity and the first physical layer entity are protocol stack entities corresponding to the second connection and/or the second cell.

In one possible design, the processing module 1001 is further configured to terminate the RRC connection reestablishment procedure when the second condition is met. Wherein the second condition may be one of: before the second communication module 1002B receives the RRC connection reestablishment message sent by the second cell, the processing module 1001 determines that the radio link problem occurring in the first cell has been recovered; before the second communication module 1002B receives the RRC connection reestablishment message sent by the second cell, the processing module 1001 determines that the leaving condition of the a3 event is satisfied; before the second communication module 1002B receives the RRC connection reestablishment message sent by the second cell, the first communication module 1002A receives a handover command sent by the first cell; and the switching command is used for switching the terminal to the second cell.

In a possible design, the processing module 1001 is further configured to disconnect the first connection after the second communication module 1002B receives the RRC connection reestablishment message sent by the second cell, if the first communication module 1002A does not receive the handover command until the second communication module 1002B receives the RRC connection reestablishment message sent by the second cell.

In a possible design, the processing module 1001 is further configured to release one or more first packet data convergence protocol PDCP entities, one or more first radio link control RLC entities, a second MAC entity, and a second physical layer entity corresponding to the first cell and/or the first connection after the second communication module 1002B receives the RRC connection reestablishment message sent by the second cell until the second communication module 1002B receives the RRC connection reestablishment message sent by the second cell and the first communication module 1002A does not receive the handover command.

It should be noted that the processing module 1001 may be one or more processors, and each of the first communication module 1002A and the second communication module 1002B may be one or more input/output circuits, communication interfaces, transceivers, rf chips, and the like.

In one possible design, the communication device 1000 may further include a storage module 1003 (see the dashed box in fig. 10). The storage module 1003 is configured to store an instruction, and the processing module 1001 is configured to execute the instruction stored by the storage module 1003, so that the processing module 1001 executes the RRC connection reestablishment method as shown in any one of fig. 3 to fig. 6.

In some embodiments, the first communication module 1002A and the second communication module 1002B may also be chips or chip systems. Wherein the chip or the chip system can be applied to a terminal.

The embodiment of the present application further provides a communication apparatus, configured to perform an RRC connection reestablishment method according to any one of the possible implementation manners of fig. 7-9. As shown in fig. 11, the communication apparatus 1100 includes: a processing module 1101, a third communication module 1102A and a fourth communication module 1102B. The processing module 1101 is configured to, when the third condition is met, initiate a radio resource control RRC connection reestablishment procedure to the fourth cell through the fourth connection while communicating with the third cell through the third connection. The third cell is a target cell in the process of cell handover executed by the terminal, the fourth cell is a cell selected by the terminal in the process of cell selection executed by the terminal, and the third communication module 1102A is used for establishing a third connection; a fourth communication module 1102B, configured to establish a fourth connection.

Wherein, the third condition may be: after the third communication module 1102A receives the handover command with the third cell as the target cell, the number of times that the third communication module 1102A sends the random access preamble to the third cell reaches the preset sending number.

In one possible design, the processing module 1101 is further configured to initiate a radio resource control, RRC, connection re-establishment procedure to a fourth cell over a fourth connection, including: and establishing a third Media Access Control (MAC) entity and a third physical layer entity, and configuring the third MAC entity and the third physical layer entity according to the public radio resource configuration information in the system information of the fourth cell. Wherein the third MAC entity and the third physical layer entity are protocol stack entities corresponding to the fourth connection and/or to the fourth cell.

In one possible design, the processing module 1101 is further configured to terminate the RRC connection reestablishment procedure when a fourth condition is met. Wherein the fourth condition is: before the fourth communication module 1102B receives the RRC connection reestablishment message sent by the fourth cell, the random access procedure of the communication apparatus on the third cell is successfully completed.

In a possible design, the processing module 1101 is further configured to disconnect the third connection after the fourth communication module 1102B receives the RRC connection reestablishment message if the communication apparatus does not successfully complete the random access procedure on the third cell until the fourth communication module 1102B receives the RRC connection reestablishment message sent by the fourth cell.

In a possible design, the processing module 1101 is further configured to release one or more second packet data convergence protocol PDCP entities, one or more second radio link control RLC entities, a fourth MAC entity, and a fourth physical layer entity corresponding to the third cell and/or the third connection after the fourth communication module 1102B receives the RRC connection reestablishment message sent by the fourth cell if the communication apparatus does not successfully complete the random access procedure on the third cell until the fourth communication module 1102B receives the RRC connection reestablishment message sent by the fourth cell.

The processing module 1101 may be one or more processors, and the third communication module 1102 and the fourth communication module 1102B may each be one or more input/output circuits, communication interfaces, transceivers, radio frequency chips, and the like.

In one possible design, the communication device 1100 may further include a storage module 1103 (see the dashed box in fig. 11). The storage module 1103 is configured to store instructions, and the processing module 1101 is configured to execute the instructions stored by the storage module 1103, so that the processing module 1101 executes the RRC connection reestablishment method as shown in any one of fig. 7-9.

In some embodiments, the communication device 1100 may be a chip or a system of chips. Wherein the chip or the chip system can be applied to a terminal.

An embodiment of the present application provides a terminal, including: a processor coupled with the memory. Wherein the memory is used for storing the computer program; a processor for executing a computer program stored in a memory to cause a terminal to perform the RRC connection reestablishment method as shown in any one of fig. 3-9.

Exemplarily, fig. 12 shows a schematic structural diagram of a terminal provided in an embodiment of the present application. The terminal shown in fig. 12 is applicable in the communication system shown in fig. 1 for performing the functions performed by the terminal in the above-described method embodiments. For convenience of explanation, fig. 12 shows only main components of the terminal. As shown in fig. 12, the terminal 1200 includes a processor, a memory, a control circuit, an antenna, and an input-output device. The processor is mainly configured to process a communication protocol and communication data, and control the entire terminal, execute a software program, and process data of the software program, for example, to support the terminal to perform the actions described in the above method embodiments, for example, when a first condition is met, while communicating with a first cell through a first connection, a radio resource control RRC connection reestablishment procedure to a second cell is initiated through a second connection, and the like. The memory is mainly used for storing software programs and data, such as entry conditions and exit conditions of the a3 event described in the above embodiments. The control circuit is mainly used for converting baseband signals and radio frequency signals and processing the radio frequency signals. The control circuit and the antenna together, which may also be called a transceiver, are mainly used for transceiving radio frequency signals in the form of electromagnetic waves. Input and output devices, such as touch screens, display screens, keyboards, etc., are used primarily for receiving data input by a user and for outputting data to the user.

When the terminal is started, the processor can read the software program in the memory, interpret and execute the instruction of the software program, and process the data of the software program. When data needs to be sent wirelessly, the processor outputs a baseband signal to the radio frequency circuit after performing baseband processing on the data to be sent, and the radio frequency circuit performs radio frequency processing on the baseband signal and sends the radio frequency signal outwards in the form of electromagnetic waves through the antenna. When data is sent to the terminal, the radio frequency circuit receives radio frequency signals through the antenna, converts the radio frequency signals into baseband signals and outputs the baseband signals to the processor, and the processor converts the baseband signals into the data and processes the data.

Those skilled in the art will appreciate that fig. 12 shows only one memory and one processor for ease of illustration. In an actual terminal, there may be multiple processors and multiple memories. The memory may also be referred to as a storage medium or a storage device, and the like, which is not limited in this embodiment of the present application.

As an implementation manner in some embodiments, the processor may include a baseband processor and a central processing unit, the baseband processor is mainly used for processing the communication protocol and the communication data, and the central processing unit is mainly used for controlling the whole terminal, executing the software program, and processing the data of the software program. The processor of fig. 12 may integrate the functions of the baseband processor and the central processing unit, and those skilled in the art will understand that the baseband processor and the central processing unit may be independent processors, and are interconnected through a bus or the like. Those skilled in the art will appreciate that the terminal may include a plurality of baseband processors to accommodate different network formats, a plurality of central processors to enhance its processing capability, and various components of the terminal may be connected by various buses. The baseband processor can also be expressed as a baseband processing circuit or a baseband processing chip. The central processing unit can also be expressed as a central processing circuit or a central processing chip. The function of processing the communication protocol and the communication data may be built in the processor, or may be stored in the storage unit in the form of a software program, and the processor executes the software program to realize the baseband processing function.

In the embodiment of the present application, an antenna and a control circuit having a transceiving function may be regarded as a transceiving unit of the terminal 1200. For example, for supporting the terminal to perform the receiving function and the transmitting function as shown in fig. 3-9. A processor with processing functionality is considered to be processing unit 1202 of terminal 1200. As shown in fig. 12, the terminal 1200 includes a transceiving unit 1201A, a transceiving unit 1201B, and a processing unit 1202. A transceiver unit may also be referred to as a transceiver, a transceiving device, etc. In some embodiments, the device for implementing the receiving function in each transceiver unit may be regarded as a receiving unit, and the device for implementing the sending function in each transceiver unit may be regarded as a sending unit, that is, the transceiver unit includes a receiving unit and a sending unit, the receiving unit may also be referred to as a receiver, an input port, a receiving circuit, and the like, and the sending unit may be referred to as a transmitter, a transmitter output port, a sending circuit, and the like.

It should be noted that the terminal 1200 shown in fig. 12 includes at least 2 sets of transceiver units, such as the transceiver unit 1201A and the transceiver unit 1201B, and each set of transceiver unit includes an independent control circuit and an independent rf antenna. In this way, the terminal 1200 may establish a first connection with a first cell via the transceiving unit 1201A and a second connection with a second cell via the transceiving unit 1201B. In other embodiments, the terminal 1200 may establish a third connection with a third cell through the transceiving unit 1201A, and establish a fourth connection with a fourth cell through the transceiving unit 1201B.

The processor 1202 may be configured to execute the instructions stored in the memory to control the transceiving unit 1201A to receive and/or transmit signals, and control the transceiving unit 1201B to receive and/or transmit signals to implement the functions of the terminal in the above-described method embodiments. As an implementation manner, the functions of the transceiving unit 1201A and the transceiving unit 1201B may be considered to be implemented by a transceiving circuit or a dedicated transceiving chip.

It should be understood that the processor in the embodiments of the present application may be a Central Processing Unit (CPU), and the processor may also be other general purpose processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, and the like. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.

It will also be appreciated that the memory in the embodiments of the subject application can be either volatile memory or nonvolatile memory, or can include both volatile and nonvolatile memory. The non-volatile memory may be a read-only memory (ROM), a Programmable ROM (PROM), an Erasable PROM (EPROM), an electrically Erasable EPROM (EEPROM), or a flash memory. Volatile memory can be Random Access Memory (RAM), which acts as external cache memory. By way of example, but not limitation, many forms of Random Access Memory (RAM) are available, such as Static RAM (SRAM), Dynamic RAM (DRAM), Synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), Enhanced SDRAM (ESDRAM), synchlink DRAM (SLDRAM), and direct bus RAM (DR RAM).

The above embodiments may be implemented in whole or in part by software, hardware (e.g., circuitry), firmware, or any combination thereof. When implemented in software, the above-described embodiments may be implemented in whole or in part in the form of a computer program product. The computer program product comprises one or more computer instructions or computer programs. The procedures or functions according to the embodiments of the present application are wholly or partially generated when the computer instructions or the computer program are loaded or executed on a computer. The computer may be a general purpose computer, a special purpose computer, a network of computers, or other programmable device. The computer instructions may be stored on a computer readable storage medium or transmitted from one computer readable storage medium to another computer readable storage medium, for example, the computer instructions may be transmitted from one website, computer, server, or data center to another website, computer, server, or data center by wire (e.g., infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server, data center, etc. that contains one or more collections of available media. The usable medium may be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium. The semiconductor medium may be a solid state disk.

It should be understood that the term "and/or" in the embodiments of the present application is only used for describing the association relationship of the associated objects, and indicates that three relationships may exist, for example, a and/or B may indicate: a exists alone, A and B exist simultaneously, and B exists alone, wherein A and B can be singular or plural. In addition, the "/" in this document generally indicates that the former and latter associated objects are in an "or" relationship, but may also indicate an "and/or" relationship, which may be understood with particular reference to the former and latter text.

In the embodiments of the present application, "at least one" means one or more, "a plurality" means two or more. "at least one of the following" or similar expressions refer to any combination of these items, including any combination of the singular or plural items. For example, at least one (one) of a, b, or c, may represent: a, b, c, a-b, a-c, b-c, or a-b-c, wherein a, b, c may be single or multiple.

In the embodiments of the present application, "first" and "second" and the like are used to distinguish different objects or to distinguish different processes on the same object, and are not used to describe a specific order of the objects.

In the embodiments of the present application, "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements listed, but may include other steps or elements not listed or inherent to such process, method, article, or apparatus in some embodiments.

In the embodiments of the present application, words such as "exemplary" or "for example" are used to mean serving as an example, instance, or illustration. Any embodiment or design described herein as "exemplary" or "e.g.," is not necessarily to be construed as preferred or advantageous over other embodiments or designs. Rather, use of the word "exemplary" or "such as" is intended to present concepts related in a concrete fashion.

In the embodiment of the present application, "information", "signal", "message", "channel", "signaling", "message" may be used in combination, and it should be noted that the intended meaning is consistent when the difference is not emphasized. "of", "corresponding", and "corresponding" may sometimes be used in combination, it being noted that the intended meaning is consistent when no distinction is made.

In the embodiments of the present application, sometimes a subscript such as W1 may be mistaken for a non-subscript form such as W1, and its intended meaning is consistent when the distinction is not emphasized.

It should be understood that, in the various embodiments of the present application, the sequence numbers of the above-mentioned processes do not mean the execution sequence, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.

Those of ordinary skill in the art will appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.

It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.

In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit.

The functions, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application or portions thereof that substantially contribute to the prior art may be embodied in the form of a software product stored in a storage medium and including instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present application. And the aforementioned storage medium includes: various media capable of storing program codes, such as a usb disk, a removable hard disk, a read-only memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.

The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present application, and shall be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. An RRC connection reestablishment method, comprising:

when the first condition is met, the terminal communicates with the first cell through the first connection and simultaneously starts a Radio Resource Control (RRC) connection reestablishment process of the second cell through the second connection; the first cell is a source cell of the terminal; the second cell is a target cell meeting the A3 event entry condition;

the terminal terminates the RRC connection reestablishment process when a second condition is met;

wherein the second condition is one of:

the terminal determines that the radio link problem occurring in the first cell is recovered before receiving the RRC connection reestablishment message sent by the second cell;

the terminal determines that the leaving condition of the A3 event is satisfied before receiving the RRC connection reestablishment message sent by the second cell;

before the terminal receives the RRC connection reestablishment message sent by the second cell, the terminal receives a switching command sent by the first cell; wherein the handover command is used for the terminal to handover to the second cell.

2. The RRC connection reestablishment method of claim 1, wherein the first condition comprises one of:

the entry condition of the A3 event is met, and the first cell has a radio link problem;

and when the entry condition of the A3 event is met, the terminal is triggered to report a measurement report to the first cell, and the first cell has a radio link problem.

3. The RRC connection reestablishment method according to claim 1 or 2, wherein the initiating of the RRC connection reestablishment procedure to the second cell through the second connection includes:

establishing a first Media Access Control (MAC) entity and a first physical layer entity, and configuring the first MAC entity and the first physical layer entity according to public radio resource configuration information in system information of the second cell; wherein the first MAC entity and the first physical layer entity are protocol stack entities corresponding to the second connection and/or the second cell.

4. The RRC connection reestablishment method according to claim 1, further comprising:

and if the terminal does not receive the switching command until the terminal receives the RRC connection reestablishment message sent by the second cell, the terminal disconnects the first connection after receiving the RRC connection reestablishment message sent by the second cell.

5. The RRC connection reestablishment method according to claim 4, further comprising:

and if the terminal does not receive the switching command until the terminal receives the RRC connection reestablishment message sent by the second cell, the terminal releases one or more first Packet Data Convergence Protocol (PDCP) entities, one or more first Radio Link Control (RLC) entities, a second MAC entity and a second physical layer entity corresponding to the first cell and/or the first connection after receiving the RRC connection reestablishment message sent by the second cell.

6. An RRC connection reestablishment method, comprising:

when the third condition is met, the terminal communicates with the third cell through the third connection and simultaneously starts a Radio Resource Control (RRC) connection reestablishment process of the fourth cell through the fourth connection; the third cell is a target cell in the process that the terminal performs cell switching, and the fourth cell is a cell selected by the terminal in the process that the terminal performs cell selection;

the terminal terminates the RRC connection reestablishment process when a fourth condition is met; wherein the fourth condition is: and the terminal successfully completes the random access process on the third cell before receiving the RRC connection reestablishment message sent by the fourth cell.

7. The RRC connection reestablishment method according to claim 6, wherein the third condition is: and after receiving a switching command which takes the third cell as a target cell, the terminal sends the random access preamble to the third cell for a preset sending time.

8. The RRC connection reestablishment method according to claim 6 or 7, wherein initiating a RRC connection reestablishment procedure to the fourth cell via the fourth connection comprises:

establishing a third Media Access Control (MAC) entity and a third physical layer entity, and configuring the third MAC entity and the third physical layer entity according to public radio resource configuration information in system information of the fourth cell; wherein the third MAC entity and the third physical layer entity are protocol stack entities corresponding to the fourth connection and/or to the fourth cell.

9. The RRC connection reestablishment method according to claim 6, further comprising:

and if the terminal does not successfully complete the random access process on the third cell until the RRC connection reestablishment message sent by the fourth cell is received, the terminal disconnects the third connection after receiving the RRC connection reestablishment message.

10. The RRC connection reestablishment method according to claim 9, further comprising:

and if the random access process on the third cell is not successfully completed by the terminal until the RRC connection reestablishment message sent by the fourth cell is received, the terminal releases one or more second Packet Data Convergence Protocol (PDCP) entities, one or more second Radio Link Control (RLC) entities, a fourth MAC entity and a fourth physical layer entity corresponding to the third cell and/or the third connection after receiving the RRC connection reestablishment message.

11. A communications apparatus, comprising: the system comprises a processing module, a first communication module and a second communication module; the processing module is configured to, when a first condition is met, initiate a radio resource control, RRC, connection reestablishment procedure to a second cell through a second connection while communicating with a first cell through a first connection; the first cell is a source cell of a terminal; the second cell is a target cell meeting the A3 event entry condition;

the first communication module is used for establishing the first connection;

the second communication module is used for establishing the second connection;

the processing module is further configured to terminate the RRC connection reestablishment procedure when a second condition is met;

wherein the second condition is one of:

12. A communications apparatus, comprising: the processing module, the third communication module and the fourth communication module; wherein the content of the first and second substances,

the processing module is configured to, when a third condition is met, initiate a radio resource control RRC connection reestablishment procedure to a fourth cell through a fourth connection while communicating with the third cell through the third connection; the third cell is a target cell in a process that a terminal executes cell switching, and the fourth cell is a cell selected by the terminal in a process that the terminal executes cell selection;

the third communication module is configured to establish the third connection;

the fourth communication module is configured to establish the fourth connection;

the processing module is further configured to terminate the RRC connection re-establishment procedure when a fourth condition is satisfied; wherein the fourth condition is: and the terminal successfully completes the random access process on the third cell before receiving the RRC connection reestablishment message sent by the fourth cell.