Mobility optimization method and related device

Abstract

A mobility optimization method and related apparatus are provided. The method includes determining connection failure information and transmitting the connection failure information and a first cell identifier to a first network device by using a radio resource control (RRC) message, the first cell identifier including an identifier of a cell from which a reconfiguration message or a handover command message received by the terminal device comes or an identifier of a cell in which a connection failure occurs, the connection failure information being in the form of a container in the RRC message and the first cell identifier being outside the container. Mobility parameters are optimized, thereby implementing mobility robustness optimization.

Description

[Technical field]

[0001] The present application relates to the field of mobile communication technologies, and in particular to a mobility optimization method and related apparatus. [Background technology]

[0002] In a mobile communication system, when a terminal device moves, the network of the terminal device is handed over from a source cell to a target cell for data transmission. In a handover (HO) procedure, if handover-related parameters (e.g., measurement filter coefficient, time-to-trigger, hysteresis threshold or trigger threshold) are improperly set, problems such as too late HO, too early HO and HO to wrong cell may be caused. As a result, the terminal device is disconnected from the network device, causing data interruption.

[0003] Currently, when a terminal device detects a connection failure (e.g., radio link failure (RLF)) or a handover failure (e.g., timer T304 expires), the terminal device performs radio resource control (RRC) re-establishment. The terminal device includes failure information of the connection failure or handover failure in an RRC re-establishment request message. The network device may determine whether the terminal device has problems such as handover too late, handover too early, and handover to a wrong cell by using the failure information in the RRC re-establishment request. Therefore, when the terminal device performs RRC re-establishment after a connection failure or handover failure, the network device determines problems such as handover too late, handover too early, and handover to a wrong cell.

[0004] However, in some cases, the terminal device does not perform RRC re-establishment. For example, in a mobility enhancement solution proposed by the 3rd generation partnership project (3GPP), if the network of the terminal device fails to be handed over from the source cell to the target cell, or if the terminal device detects an RLF in the source cell after the terminal device receives a handover message and before a random access channel (RACH) procedure in the target cell is successful, the terminal device does not perform RRC re-establishment. For another example, in Multi-Radio dual connectivity (MR-DC) in the 5th generation mobile networks (5G) standard Release R16, if the terminal device detects an RLF in a master cell group (MCG), the terminal device does not perform RRC re-establishment. Therefore, in these cases, if the terminal device does not perform RRC re-establishment, how to determine a handover that is too late, too early, and a handover to a wrong cell becomes an urgent problem to be solved. Summary of the Invention

[0005] An embodiment of the present application provides a mobility optimization method and related apparatus to implement mobility robustness optimization by determining too late handover, too early handover and handover to an incorrect cell in mobility enhancement and / or MR-DC proposed by 3GPP (registered trademark) and optimizing mobility parameters.

[0006] In the following, the present application will be described from different aspects, and it should be understood that cross-reference may be made to the following implementations and beneficial effects of the different aspects.

[0007] According to a first aspect, an embodiment of the present application provides a mobility optimization method. The method includes: a terminal device sending connection failure information to a first network device; and the first network device determining a connection failure type of the terminal device after receiving the connection failure information. Optionally, the first network device may optimize mobility parameters after determining the connection failure type of the terminal device. The mobility parameters may include one or more of a measurement filter coefficient, a corresponding measurement trigger threshold or period, a time to trigger, or a hysteresis threshold. The connection failure information may be used to indicate that the terminal device detects an RLF in a first cell or fails to be handed over to the first cell. There is a radio connection between the terminal device and a second cell in a handover procedure from the second cell to the first cell, and the second cell is a cell managed by the first network device. The connection failure type may include a premature handover and / or a handover to a wrong cell. The connection failure type may be used for mobility robustness optimization.

[0008] Optionally, the first cell is a target cell, the second cell is a source cell, and the first network device is a source base station. The first cell (target cell) and the second cell (source cell) may be cells managed by the same network device. That is, both the first cell and the second cell are cells managed by the first network device. The first cell and the second cell may alternatively be cells managed by different network devices. For example, the second cell is a cell managed by the first network device, and the first cell is a cell managed by the second network device.

[0009] In this embodiment of the present application, after the terminal device detects an RLF in a target cell or fails to be handed over to the target cell, the terminal device sends connection failure information to a first network device (source base station). The connection failure information may trigger the first network device to determine the connection failure type (premature handover or handover to a wrong cell) of the terminal device. After receiving the connection failure information, the first network device determines the connection failure type of the terminal device. The connection failure type can be used for mobility robustness optimization. In this way, premature handover and handover to a wrong cell are determined in a mobility enhancement scenario, and mobility parameters are optimized, thereby implementing mobility robustness optimization.

[0010] In relation to the first aspect, in a possible implementation, the first network device specifically determines the connection failure type of the terminal device as follows: That is, if the first network device determines that the terminal device still holds a radio connection to the second cell (source cell) after the terminal device detects an RLF in the first cell (target cell) or fails to be handed over to the first cell (target cell) (or the first network device determines that the terminal device is camped on the source cell), the first network device determines that the connection failure type of the terminal device is premature handover; or if the first network device determines that the third cell is the cell accessed by the terminal device (or the first network device determines that the terminal device is handed over to a new target cell), the first network device determines that the connection failure type of the terminal device is handover to an incorrect cell. The third cell is different from the first cell (i.e., the target cell) and the second cell (i.e., the source cell). In a handover procedure from the second cell to the first cell, the existence of a radio connection between the terminal device and the second cell means that the terminal device can perform data communication in the second cell (source cell).

[0011] The present embodiment of the present application provides a criterion for determining premature handover and handover to a wrong cell in a mobility enhancement scenario. That is, when the first network device determines that the terminal device is camped on the source cell, the first network device determines that the connection failure type of the terminal device is premature handover, or when the first network device determines that the terminal device is handed over to a new target cell, the first network device determines that the connection failure type of the terminal device is handover to a wrong cell. In this way, premature handover and handover to a wrong cell are determined in a mobility enhancement scenario, and mobility parameters are optimized, thereby implementing mobility robustness optimization.

[0012] In relation to the first aspect, in a possible implementation, the first cell is a candidate cell that is in at least one candidate cell of the terminal device and satisfies a conditional handover CHO trigger condition, and the third cell is different from any one of the second cell and the at least one candidate cell. In the procedure of handover from the second cell to the first cell, the existence of a radio connection between the terminal device and the second cell means that the terminal device holds a connection configuration in the second cell (source cell) but cannot perform data communication. According to this embodiment of the present application, premature handover and handover to a wrong cell can be determined in a conditional handover CHO scenario.

[0013] In relation to the first aspect, in a possible implementation, before the first network device receives the connection failure information from the terminal device, the method further includes a step of the first network device sending a first indication information to the terminal device, the first indication information being used to indicate the terminal device to access a second cell (source cell) if the terminal device fails to be handed over to the first cell (target cell). According to this embodiment of the present application, in a CHO scenario, if the random access to the target cell fails, a rollback to communication in the source cell may be performed.

[0014] According to a second aspect, an embodiment of the present application provides another mobility optimization method. The method includes: when a terminal device detects an RLF in a first cell in a handover procedure from a first cell to a second cell, the terminal device may transmit connection failure information to a second network device after receiving the connection failure information, and the terminal device may determine a connection failure type of the terminal device after receiving the connection failure information. Optionally, the first network device may optimize mobility parameters after determining the connection failure type of the terminal device. The mobility parameters may include one or more of a measurement filter coefficient, a corresponding measurement trigger threshold or period, a time to trigger or a hysteresis threshold, etc. The connection failure information may be used to indicate that the terminal device detects an RLF in a first cell in a handover procedure from a first cell (i.e., a source cell) to a second cell (i.e., a target cell). In the handover procedure, before the terminal device detects the RLF in the source cell, the terminal device holds a radio connection to the source cell. When the terminal device detects the RLF in the source cell, the radio connection between the terminal device and the source cell is disconnected. That is, the terminal device cannot perform data communication in the source cell in this case. The first cell is a cell managed by the first network device. The connection failure type may include a too late handover. The connection failure type may be used for mobility robustness optimization.

[0015] Optionally, the first cell is a source cell, the second cell is a target cell, and the first network device is a source base station. The first cell (source cell) and the second cell (target cell) may be cells managed by the same network device. That is, both the first cell and the second cell are cells managed by the first network device, and the first network device and the second network device are the same physical device. The first cell and the second cell may alternatively be cells managed by different network devices. For example, the second cell is a cell managed by the first network device, and the first cell is a cell managed by the second network device.

[0016] In this embodiment of the present application, the terminal device transmits connection failure information to the second network device after detecting the RLF in the source cell in the procedure of handover from the first cell to the second cell, and the second network device may transmit the connection failure information to the first network device after receiving the connection failure information. The connection failure information may trigger the first network device to determine the connection failure type (too late handover) of the terminal device. The first network device determines the connection failure type of the terminal device after receiving the connection failure information. The connection failure type may be used for mobility robustness optimization. In this way, too late handover is determined in a mobility enhancement scenario, and mobility parameters are optimized, thereby implementing mobility robustness optimization.

[0017] In relation to the second aspect, in a possible implementation, the first network device determines the connection failure type of the terminal device as follows: That is, when the first network device determines that the time that the terminal device camps on the first cell (source cell) is greater than a second threshold (or the first network device determines that the time that the terminal device camps on the source cell is too long), and the terminal device successfully accesses the second cell (target cell), the first network device determines that the connection failure type of the terminal device is too late handover.

[0018] In this application, the time that a terminal device is camped on a first cell is the time that the terminal device maintains an RRC connection to the first cell, or the time that the terminal device maintains a radio connection to the first cell, or the time that the terminal device has a connection to the first cell but has not received a handover command.

[0019] This embodiment of the present application provides a criterion for determining handover too late in a mobility enhancement scenario. That is, when the first network device determines that the terminal device camps on the source cell for too long, and the terminal device successfully accesses the target cell, the first network device determines that the connection failure type of the terminal device is handover too late. In this way, handover too late is determined in a mobility enhancement scenario, and mobility parameters are optimized, thereby implementing mobility robustness optimization.

[0020] In relation to the second aspect, in a possible implementation, the second cell is a candidate cell that is in at least one candidate cell of the terminal device and meets a CHO trigger condition. According to this embodiment of the present application, a too late handover can be determined in a CHO scenario.

[0021] According to a third aspect, an embodiment of the present application provides yet another mobility optimization method. The method includes: when a terminal device detects an RLF in a master cell group MCG, sending connection failure information to a second network device; after the second network device receives the connection failure information, forwarding the connection failure information to the first network device; and after the first network device receives the connection failure information, determining a connection failure type of the terminal device. Optionally, the first network device may optimize mobility parameters after determining the connection failure type of the terminal device. The mobility parameters may include one or more of a measurement filter coefficient, a corresponding measurement trigger threshold or period, a time to trigger or a hysteresis threshold, etc. The connection failure information may be used to indicate that the terminal device detects an RLF in an MCG managed by the first network device. The connection failure types may include a handover that is too late, a handover that is too early, and a handover to a wrong cell. The connection failure type may be used for mobility robustness optimization. The second network device is a secondary network device (also called a secondary node) SN.

[0022] In this embodiment of the present application, the terminal device may send connection failure information to a second network device (SN) after detecting an RLF in an MCG managed by a first network device, and the second network device may send connection failure information to the first network device after receiving the connection failure information. The connection failure information may trigger the first network device to determine the connection failure type of the terminal device (handover too late, handover too early, or handover to a wrong cell). The first network device may determine the connection failure type of the terminal device after receiving the connection failure information. The connection failure type may be used for mobility robustness optimization. In this way, handover too late, handover too early, or handover to a wrong cell is determined in a dual connectivity scenario, and mobility parameters are optimized, thereby implementing mobility robustness optimization.

[0023] In relation to the third aspect, in a possible implementation, the first network device determines the connection failure type of the terminal device specifically as follows: That is, if the first network device determines that a fourth cell (e.g., cell D) is the cell accessed by the terminal device (or the primary cell PCell of the terminal device has changed to a new cell different from the primary cell in the MCG managed by the first network device, e.g., the primary cell PCell of the terminal device has changed from cell A to cell D), the first network device determines that the connection failure type of the terminal device is too late handover. The fourth cell is different from the primary cell in the MCG managed by the first network device. The first network device is a source master network device (also referred to as a source master node), i.e., a source MN.

[0024] This embodiment of the present application provides a criterion for determining a too late handover in a dual connectivity scenario. That is, when the first network device determines that the primary cell PCell of the terminal device has changed to a new cell, the first network device determines that the connection failure type of the terminal device is a too late handover. In this way, a too late handover is determined in a dual connectivity scenario, and mobility parameters are optimized, thereby implementing mobility robustness optimization.

[0025] In relation to the third aspect, in a possible implementation, the first network device determines the connection failure type of the terminal device as follows: That is, when the first network device determines that the source master network device has recently sent a handover message to the terminal device, which is used to indicate that the primary cell has changed (e.g., the primary cell has changed from cell A to cell B), and determines that a fifth cell (e.g., cell A) is the cell accessed by the terminal device (or determines that the terminal device is camped on an unchanged primary cell, e.g., cell A), the first network device determines that the connection failure type of the terminal device is premature handover. The fifth cell is the cell accessed before the primary cell in the MCG managed by the first network device is handed over. If the first network device determines that the source master network device has recently sent a handover message to the terminal device, used to indicate that the primary cell has changed (e.g., the primary cell has changed from cell A to cell B), and determines that a sixth cell (e.g., cell C) is the cell accessed by the terminal device (or determines that the terminal device has been handed over to a new primary cell, which is a new primary cell and is different from cells A and B), the first network device determines that the connection failure type of the terminal device is handover to an incorrect cell. The sixth cell is different from the primary cell and the fifth cell in the MCG managed by the first network device. The first network device is the target master network device, i.e., the target MN.

[0026] This embodiment of the present application provides a criterion for determining premature handover and handover to an incorrect cell in a dual connectivity scenario. That is, when the first network device determines that the source master network device has recently sent a handover message to the terminal device, which is used to indicate that the primary cell has changed, and the terminal device is camped on the unchanged primary cell, the first network device determines that the connection failure type of the terminal device is premature handover. When the first network device determines that the source master network device has recently sent a handover message to the terminal device, which is used to indicate that the primary cell has changed, and the terminal device is handed over to a new primary cell, the first network device determines that the connection failure type of the terminal device is handover to an incorrect cell. In this way, premature handover and handover to an incorrect cell are determined in a dual connectivity scenario, and mobility parameters are optimized, thereby implementing mobility robustness optimization.

[0027] In relation to the third aspect, in a possible implementation, the first network device is a target master network device. After the first network device determines the connection failure type of the terminal device, the method further includes the first network device sending second indication information to the source master network device, where the second indication information can be used to indicate that the connection failure type of the terminal device is premature handover or handover to an incorrect cell.

[0028] According to a fourth aspect, an embodiment of the present application provides yet another mobility optimization method. The method includes: a terminal device sending connection failure information when the terminal device detects an RLF in a first cell or fails to be handed over from the first cell to a second cell; and a first network device determining a connection failure type of the terminal device after receiving the connection failure information. Optionally, the first network device may optimize mobility parameters after determining the connection failure type of the terminal device. The mobility parameters may include one or more of a measurement filter coefficient, a corresponding measurement trigger threshold or period, a time to trigger or a hysteresis threshold, etc. The connection failure information may be used to indicate that the terminal device detects an RLF in the first cell or fails to be handed over from the first cell to the second cell. The connection failure types may include a handover that is too late, a handover that is too early, and a handover to a wrong cell. The connection failure type may be used for mobility robustness optimization.

[0029] In relation to the fourth aspect, in a possible implementation, the first cell is a source cell managed by the first network device, the first network device is a source base station, the second cell is a target cell, and the connection failure information is used to indicate that the terminal device detects RLF in the first cell (source cell). Specifically, the first network device determines the connection failure type of the terminal device as follows: That is, if the first network device determines that the time that the terminal device camps on the first cell (source cell) is greater than a second threshold (or the first network device determines that the time that the terminal device camps on the source cell is too long), and the terminal device successfully accesses the second cell (i.e., the target cell), the first network device determines that the connection failure type of the terminal device is too late handover. The second cell is a candidate cell that is in at least one candidate cell of the terminal device and meets the CHO trigger condition.

[0030] This embodiment of the present application provides a criterion for determining too late handover in a CHO scenario. That is, when the first network device determines that the terminal device camps on the source cell for too long, and the terminal device successfully accesses the target cell, the first network device determines that the connection failure type of the terminal device is too late handover. In this way, too late handover is determined when RRC re-establishment is not performed in a CHO scenario, and mobility parameters are optimized, thereby implementing mobility robustness optimization.

[0031] In relation to the fourth aspect, in a possible implementation, the first cell is a source cell, the second cell is a target cell, and the second cell is a candidate cell that is in at least one candidate cell of the terminal device and satisfies a CHO trigger condition. Before the first network device receives the connection failure information, the method further includes a step of the first network device sending first indication information to the terminal device, the first indication information being used to indicate the terminal device to access the first cell when the terminal device fails to be handed over from the first cell to the second cell. According to this embodiment of the present application, in a CHO scenario, if random access to the target cell fails, a rollback to communication in the source cell may be performed.

[0032] In relation to the fourth aspect, in a possible implementation, the first cell is a source cell, the second cell is a target cell, the second cell is a candidate cell that is in at least one candidate cell of the terminal device and satisfies the CHO trigger condition, and the connection failure information is used to indicate that the terminal device fails to be handed over from the first cell to the second cell (target cell). Specifically, the first network device determines the connection failure type of the terminal device as follows: That is, if the first network device determines that the terminal device continues to hold a radio connection to the first cell (i.e., the source cell) after the terminal device successfully re-accesses the first cell (or the first network device determines that the terminal device is camped on the source cell), the first network device determines that the connection failure type of the terminal device is premature handover. If the first network device determines that the third cell is the cell accessed by the terminal device (or the first network device determines that the terminal device is handed over to a new target cell), the first network device determines that the connection failure type of the terminal device is a handover to an incorrect cell. The third cell is different from the first cell (i.e., the source cell) and any one of the one or more candidate cells.

[0033] This embodiment of the present application provides a criterion for determining premature handover and handover to a wrong cell in a CHO scenario. If the first network device determines that the terminal device is camped on the source cell, the first network device determines that the connection failure type of the terminal device is premature handover. If the first network device determines that the terminal device is handed over to a new target cell, the first network device determines that the connection failure type of the terminal device is handover to a wrong cell. In this way, premature handover and handover to a wrong cell are determined when RRC re-establishment is not performed in a CHO scenario, and mobility parameters are optimized, thereby implementing mobility robustness optimization.

[0034] According to a fifth aspect, an embodiment of the present application provides an apparatus. The apparatus may be a network device, or a chip or circuit that may be disposed in the network device. The apparatus includes a unit and / or a module configured to perform the mobility optimization method according to the first aspect and / or any one of the possible implementations of the first aspect, and thus may also realize the beneficial effects (or advantages) of the mobility optimization method provided in the first aspect.

[0035] According to a sixth aspect, an embodiment of the present application provides an apparatus. The apparatus may be a network device, or a chip or circuit that may be disposed in the network device. The apparatus includes a unit and / or a module configured to perform the mobility optimization method according to the second aspect and / or any one of the possible implementations of the second aspect, and thus may also realize the beneficial effects (or advantages) of the mobility optimization method provided in the second aspect.

[0036] According to a seventh aspect, an embodiment of the present application provides an apparatus. The apparatus may be a network device, or a chip or circuit that may be disposed in the network device. The apparatus includes a unit and / or a module configured to perform the mobility optimization method according to the third aspect and / or any one of the possible implementations of the third aspect, and thus may also realize the beneficial effects (or advantages) of the mobility optimization method provided in the third aspect.

[0037] According to an eighth aspect, an embodiment of the present application provides an apparatus. The apparatus may be a network device, or a chip or circuit that may be disposed in the network device. The apparatus includes a unit and / or a module configured to perform the mobility optimization method according to the fourth aspect and / or any one of the possible implementations of the fourth aspect, and thus may also realize the beneficial effects (or advantages) of the mobility optimization method provided in the fourth aspect.

[0038] According to a ninth aspect, an embodiment of the present application provides an apparatus. The apparatus may be a network device, or a chip or circuit that may be disposed in the network device. The apparatus may include a processor, a transceiver, and a memory. The memory is configured to store a computer program, and the transceiver is configured to receive and transmit various types of information, and the computer program includes program instructions, and when the processor executes the program instructions, the apparatus is enabled to perform the mobility optimization method according to the first aspect or any one of the possible implementations of the first aspect. The transceiver may be a radio frequency module in the network device, or a combination of a radio frequency module and an antenna, or an input / output interface of the chip or circuit.

[0039] According to a tenth aspect, an embodiment of the present application provides an apparatus. The apparatus may be a network device, or a chip or circuit that may be disposed in the network device. The apparatus may include a processor, a transceiver, and a memory. The memory is configured to store a computer program, and the transceiver is configured to receive and transmit various types of information, and the computer program includes program instructions, and when the processor executes the program instructions, the apparatus is enabled to perform the mobility optimization method according to the second aspect or any one of the possible implementations of the second aspect. The transceiver may be a radio frequency module in the network device, or a combination of a radio frequency module and an antenna, or an input / output interface of the chip or circuit.

[0040] According to an eleventh aspect, an embodiment of the present application provides an apparatus. The apparatus may be a network device, or a chip or circuit that may be disposed in the network device. The apparatus may include a processor, a transceiver, and a memory. The memory is configured to store a computer program, and the transceiver is configured to receive and transmit various types of information, and the computer program includes program instructions, and when the processor executes the program instructions, the apparatus is enabled to perform a mobility optimization method according to the third aspect or any one of the possible implementations of the third aspect. The transceiver may be a radio frequency module in the network device, or a combination of a radio frequency module and an antenna, or an input / output interface of the chip or circuit.

[0041] According to a twelfth aspect, an embodiment of the present application provides an apparatus. The apparatus may be a network device, or a chip or circuit that may be disposed in the network device. The apparatus may include a processor, a transceiver, and a memory. The memory is configured to store a computer program, and the transceiver is configured to receive and transmit various types of information, and the computer program includes program instructions, and when the processor executes the program instructions, the apparatus is enabled to perform the mobility optimization method according to the fourth aspect or any one of the possible implementations of the fourth aspect. The transceiver may be a radio frequency module in the network device, or a combination of a radio frequency module and an antenna, or an input / output interface of the chip or circuit.

[0042] According to a thirteenth aspect, an embodiment of the present application provides a communication system including a first network device and a terminal device, the first network device being a network device in the mobility optimization method described in the first aspect or the fourth aspect, and the terminal device being a terminal device in the mobility optimization method described in the first aspect or the fourth aspect.

[0043] According to a fourteenth aspect, an embodiment of the present application provides a communication system including a first network device, a second network device, and a terminal device, where the first network device is the first network device in the mobility optimization method described in the second aspect, the third aspect, or any one of the possible implementations of the second aspect or the third aspect, the second network device is the second network device in the mobility optimization method described in the second aspect, the third aspect, or any one of the possible implementations of the second aspect or the third aspect, and the terminal device is the terminal device in the mobility optimization method described in the second aspect, the third aspect, or any one of the possible implementations of the second aspect or the third aspect.

[0044] According to a fifteenth aspect, an embodiment of the present application provides a readable storage medium, which stores instructions that, when executed on a computer, enable the computer to perform the mobility optimization method described in the first aspect or any one of the possible implementations of the first aspect.

[0045] According to a sixteenth aspect, an embodiment of the present application provides a readable storage medium, storing instructions which, when executed on a computer, enable the computer to perform the mobility optimization method described in the second aspect or any one of the possible implementations of the second aspect.

[0046] According to a seventeenth aspect, an embodiment of the present application provides a readable storage medium, which stores instructions that, when executed on a computer, enable the computer to perform a mobility optimization method as described in the third aspect or any one of the possible implementations of the third aspect.

[0047] According to an eighteenth aspect, an embodiment of the present application provides a readable storage medium, which stores instructions that, when executed on a computer, enable the computer to perform the mobility optimization method described in the fourth aspect or any one of the possible implementations of the fourth aspect.

[0048] According to a nineteenth aspect, an embodiment of the present application provides a program product comprising instructions, which when executed, perform a mobility optimization method as described in the first aspect or any one of the possible implementations of the first aspect.

[0049] According to a twentieth aspect, an embodiment of the present application provides a program product comprising instructions, which when executed, perform a mobility optimization method as described in the second aspect or any one of the possible implementations of the second aspect.

[0050] According to a twenty-first aspect, an embodiment of the present application provides a program product comprising instructions, which when executed, performs a mobility optimization method as described in the third aspect or any one of the possible implementations of the third aspect.

[0051] According to a twenty-second aspect, an embodiment of the present application provides a program product comprising instructions, which when executed, perform a mobility optimization method as described in the fourth aspect or any one of the possible implementations of the fourth aspect.

[0052] According to a twenty-third aspect, an embodiment of the present application provides a chip including a processor. The processor is configured to read and execute a program stored in a memory to execute a mobility optimization method provided in one or more of the first to fourth aspects, or any one of the possible implementations of the first, second, third or fourth aspects. Optionally, the chip further includes a memory, the memory being connected to the processor by using a circuit or a wire. Furthermore, optionally, the chip further includes a communication interface, the processor being connected to the communication interface. The communication interface is configured to receive data and / or information that needs to be processed. The processor obtains the data and / or information from the communication interface, processes the data and / or information, and outputs the processing result through the communication interface. The communication interface may be an input / output interface.

[0053] Optionally, the processor and memory may be physically separate units, or the memory may be integrated with the processor.

[0054] According to an embodiment of the present application, mobility robustness optimization is implemented by being able to determine handover too late, too early and handover to an incorrect cell in mobility enhancement and / or MR-DC proposed by 3GPP (registered trademark) and by being able to optimize mobility parameters. [Brief description of the drawings]

[0055] [Figure 1A] 1 is a schematic diagram of a system architecture of a mobile communication system according to an embodiment of the present application;

[0056] [Figure 1B] FIG. 2 is a schematic diagram of a base station division into separate CU and DU according to one embodiment of the present application;

[0057] [Diagram 2] 1 is a first schematic flowchart of a mobility optimization method according to an embodiment of the present application;

[0058] [Diagram 3] 2 is a second schematic flowchart of a mobility optimization method according to an embodiment of the present application;

[0059] [Figure 4] 4 is a third schematic flowchart of a mobility optimization method according to an embodiment of the present application;

[0060] [Diagram 5] 4 is a fourth schematic flowchart of a mobility optimization method according to an embodiment of the present application;

[0061] [Figure 6] 5 is a fifth schematic flowchart of a mobility optimization method according to an embodiment of the present application;

[0062] [Figure 7] 1 is a schematic flowchart of a mobility optimization method for different RATs according to an embodiment of the present application;

[0063] [Figure 8] FIG. 1 is a schematic structural diagram of an apparatus according to an embodiment of the present application;

[0064] [Figure 9] FIG. 2 is another schematic structural diagram of an apparatus according to an embodiment of the present application.

[0065] [Figure 10] FIG. 2 is yet another schematic structural diagram of an apparatus according to an embodiment of the present application.

[0066] [Figure 11] 1 is a schematic structural diagram of a communication device according to an embodiment of the present application; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0067] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following clearly and completely describes the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application.

[0068] In order to better understand the mobility optimization method provided in the embodiments of the present application, the following briefly describes some terms (nouns) in the mobility optimization method provided in the embodiments of the present application.

[0069] 1. Radio link failure (RLF)

[0070] In Long Term Evolution (LTE) for universal mobile communication technology, when a terminal device finds that a problem occurs in communication with the network side, this is considered as a radio link failure occurring between the network device and the terminal device. The radio link failure detection mechanism includes one or more of the following: (1) A problem in the physical layer is detected. For example, the RRC layer of the terminal device receives N consecutive out-of-sync indications of the primary cell (PCell) from the lower layer, but does not receive M consecutive in-sync indications of the primary cell (PCell) from the lower layer in a subsequent period of time. (2) A random access procedure performed in the master cell group fails. (3) The RRC layer of the terminal device receives indication information from the master cell group radio link control (RLC) layer indicating that the maximum number of retransmissions has been reached.

[0071] [2. Handover failure]

[0072] Inter-cell handover means that the terminal device completes the transition of the radio link connection from a source cell to a target cell under the control of the radio access network. Usually, after the terminal device receives a handover message (e.g., an RRC Reconfiguration message carrying reconfigurationWithSync), the terminal device starts the timer T304. If the terminal device successfully completes the random access in the target cell, the terminal device stops the timer T304, which indicates that the terminal device has been successfully handed over from the source cell to the target cell. If the timer T304 expires before the terminal device successfully completes the random access in the target cell, the terminal device fails to be handed over from the source cell to the target cell.

[0073] [3. Too late handover]

[0074] A too late handover means that a connection failure occurs after the terminal device is connected to the current serving cell for a certain period of time (e.g., an RLF is detected in the current serving cell), and the terminal device attempts to re-establish a connection to another cell (the other cell is any cell). This case mainly means that the quality of the current serving cell has deteriorated, but the terminal device has not received a handover message, and therefore the terminal device attempts to re-establish a connection to another cell after detecting a connection failure in the current serving cell.

[0075] [4. Too early handover]

[0076] Premature handover means that a connection failure occurs shortly after the terminal device has been successfully handed over from the source cell to the target cell (e.g., RLF is detected in the target cell), or that a handover failure occurs during the handover procedure from the source cell to the target cell and the terminal device attempts to re-establish a connection to the source cell. The term "soon" in this specification may be understood as a short period of time.

[0077] [5. HO to wrong cell]

[0078] A handover to an incorrect cell means that a connection failure occurs shortly after the terminal device is successfully handed over from the source cell to the target cell (e.g., RLF is detected in the target cell), or that a handover failure occurs during the handover procedure from the source cell to the target cell, and the terminal device attempts to re-establish a connection to another cell (the other cell is different from the source cell and the target cell). The term "shortly" in this specification may be understood as a short period of time.

[0079] [6. Master cell group (MCG) and secondary cell group (SCG)]

[0080] In a 5G wireless network, one terminal device may communicate with multiple network devices. That is, dual connectivity (DC), which is also referred to as multi-radio dual connectivity (MR-DC). The multiple network devices may be network devices of the same standard (e.g., the multiple network devices are all fourth generation (4G) base stations or all fifth generation (5G) base stations), or may be base stations of different standards (e.g., one base station is a 4G base station and the other base station is a 5G base station). In DC, a network device (base station) that exchanges control plane signaling with a core network (CN) is referred to as a master node (MN), and the other network device (base station) is referred to as a secondary node (SN). The MN may be referred to as a master base station, and the SN may be referred to as a secondary base station. The cells served by the master base station are referred to as a master cell group, which may include a primary cell (PCell) and one or more optional secondary cells. The cells served by the secondary base station are referred to as a secondary cell group, which may include a primary secondary cell (PSCell) and one or more optional secondary cells.

[0081] [7. Primary Cell (PCell) and Primary Secondary Cell (PSCell)]

[0082] A primary cell is an MCG cell deployed on a primary frequency, in which the terminal device performs an initial connection establishment procedure or a connection re-establishment procedure, or designates this cell as a primary cell in a handover procedure. A primary secondary cell is a cell in an SCG cell and in which the terminal device performs random access when the terminal device performs a synchronous reconfiguration procedure, or in which the terminal device starts initial physical uplink share channel (PUSCH) transmission during a change of SCG without the need for a random access procedure.

[0083] [8. Mobility robust optimization (MRO)]

[0084] The main objective of mobility robustness optimization is to reduce the number of handover-related RLFs and improve the network resource usage efficiency. Suboptimal handover parameter configurations may cause severe service performance degradation even without causing RLFs, affecting user experience. For example, incorrect setting of handover hysteresis may cause ping-pong effect or delay access to suboptimal cells even without causing RLFs. Another objective of mobility robustness optimization is to reduce inefficient use of network resources caused by unnecessary or missed handovers. Mobility robustness optimization mainly adjusts handover thresholds based on performance indicator feedback and adaptively adjusts cell parameters to meet the thresholds.

[0085] The above description briefly describes some terms (nouns) in the mobility optimization method provided in the embodiment of the present application. The following describes the system architecture of the mobility optimization method provided in the embodiment of the present application.

[0086] The mobility optimization method provided in the embodiment of the present application can be applied to a mobile communication system, for example, a second generation / third generation / fourth generation mobile communication system (2G / 3G / 4G) or a 5G or future mobile communication system. For ease of understanding, the system architecture of the mobile communication system is first briefly described in the embodiment of the present application.

[0087] FIG. 1A is a schematic diagram of a system architecture of a mobile communication system according to an embodiment of the present application. As shown in FIG. 1A, the mobile communication system may include at least two network devices (for example, the network device 110 and the network device 120 in FIG. 1A), at least one core network device 130 and at least one terminal device 140. The terminal device 140 may be wirelessly connected to the network devices. The network device 110 and the network device 120 may access the core network device 130 together. FIG. 1A is only a schematic diagram. The mobile communication system may further include another network device, for example, a wireless relay device and / or a wireless backhaul device not shown in FIG. 1A. The number of network devices, terminal devices and core network devices included in the mobile communication system is not limited in this embodiment of the present application.

[0088] The core network device 130 may be a 4G core network device or a 5G core network device.

[0089] The network device may be an entity, for example, a gNB configured to transmit or receive signals on the network side. Alternatively, the network device may be an access device that wirelessly connects a terminal device to a mobile communication system. For example, the network device may be a base station NodeB, an evolved base station (eNB), a transmission reception point (TRP), a next generation base station (gNB) in a 5G mobile communication system, or a base station in a future mobile communication system. The specific technology used by the network device and the specific device form are not limited in this embodiment of the present application.

[0090] Optionally, the base station in this embodiment of the present application may be a base station (herein referred to as gNB) with a centralized unit (CU) and a distributed unit (DU) separated. FIG. 1B is a schematic diagram of a base station with a CU and a DU separated according to an embodiment of the present application. One base station (herein referred to as gNB) may include one CU and multiple DUs. The CU may be connected to the DU through an F1 interface. FIG. 1B shows only one example of the relationship between one CU and one DU. As shown in FIG. 1B, the CU may be divided into a centralized unit control plane (CU-control plane, CU-CP) and a centralized unit user plane (CU-user plane, CU-UP). The CU-CP and the CU-UP may be on different physical devices, and the CU-CP may be connected to the CU-UP through an E1 interface. The CU-CP may be connected to the DU through an F1-C interface, and the CU-UP may be connected to the DU through an F1-U interface. The CU-CP may include a radio resource control layer (RRC layer) and a packet data convergence protocol (PDCP) layer control plane. The CU-UP may include a service data adaptation protocol (SDAP) layer and a PDCP user plane. The DU may include a radio link control layer (RLC layer), a medium access control (MAC) layer, and a physical (PHY) layer.

[0091] The terminal device 140 may be an entity, for example, a mobile phone UE, configured to receive or transmit signals at a user side. The terminal device in this embodiment of the present application may be a mobile terminal device. For example, the terminal device may be a user equipment (UE), a mobile station (MS) or a mobile terminal (MT), and may be a mobile portable terminal device, such as a mobile phone, a tablet computer (pad) or a computer with a radio transceiver function. The specific technology and the specific device form used by the mobile terminal device are not limited in this embodiment of the present application.

[0092] In some possible implementations, the terminal device 140 may be connected to one or more network devices. For example, the terminal device 140 may communicate with the network device 110 and the network device 120 by using a dual connectivity (DC) technology. The dual connectivity (DC) type includes one or more of Evolved Universal Terrestrial Radio Access and New Radio Dual Connectivity (E-UTRA-NR dual connectivity, EN-DC), Next Generation Radio Access Network Evolved Universal Terrestrial Radio Access New Radio Dual Connectivity (NG-RAN E-UTRA-NR dual connectivity, NGEN-DC), New Radio Evolved Universal Terrestrial Radio Access Dual Connectivity (NR-E-UTRA dual connectivity, NE-DC), and New Radio and New Radio Dual Connectivity (NR-NR dual connectivity, NR-DC).

[0093] In EN-DC, a master base station (master network device) is an LTE base station (e.g., an eNB) connected to a 4G core network, and a secondary base station (secondary network device) is an NR base station (e.g., a gNB).

[0094] In NGEN-DC, the master base station (master network device) is an LTE base station connected to the 5G core network, and the secondary base station (secondary network device) is an NR base station.

[0095] In NE-DC, the master base station (master network device) is an NR base station connected to the 5G core network, and the secondary base station (secondary network device) is an LTE base station.

[0096] In NR-DC, the master base station (master network device) is an NR base station connected to the 5G core network, and the secondary base station (secondary network device) is an NR base station.

[0097] The above description describes the system architecture of the mobility optimization method provided in the embodiment of the present application. In the following, the mobility optimization method provided in the embodiment of the present application will be described in detail with reference to application scenarios.

[0098] [Application scenario 1: Improving mobility]

[0099] In order to improve user experience and system performance, 3GPP requires that the mobility interruption delay is 0 ms (milliseconds) in the handover procedure (both the uplink interruption delay and the downlink interruption delay need to be 0 ms or close to 0 ms). Therefore, 3GPP proposes a mobility enhancement solution to realize a mobility interruption delay of 0 ms. In the mobility enhancement solution, the source base station sends a handover message (e.g., an RRC Conn Reconfig with Mobility Control Info message) to the terminal device (e.g., a UE), and then may perform data forwarding with the target base station. In addition, if the terminal device is synchronized with the target cell, it still keeps a connection to the source cell. For the downlink, in the handover procedure, the data transmission between the source base station and the terminal device is not interrupted, and both the target base station and the source base station may transmit downlink data to the terminal device, thereby reducing the data transmission interruption time. Therefore, in the mobility enhancement solution, the terminal device may simultaneously perform data communication with the source base station and the target base station. Optionally, the mobility enhancement solution may also be applied to a scenario where the source cell and the target cell belong to the same base station (i.e., the source base station and the target base station are one physical entity), with the difference being that there is no data forwarding procedure between the source base station and the target base station. Optionally, the mobility enhancement solution may be referred to as dual active protocol stack (DAPS) handover.

[0100] In the mobility enhancement solution, the terminal device still holds a radio connection to the source cell (holding a radio connection means that the terminal device can perform data communication in the source cell) during the handover procedure (the handover procedure starts from the time when the source base station sends a handover message and ends when the source base station releases the UE's context). Therefore, if the terminal device fails to access the target cell (meaning that the handover to the target cell fails or the RLF occurs immediately after the access to the target cell is successful), the terminal device does not perform RRC re-establishment, and the terminal device sends one handover failure indication information to the source cell. Optionally, if the terminal device detects an RLF in the source cell after the terminal device receives the handover message and before the RACH procedure in the target cell is successful, the terminal device also does not perform RRC re-establishment. Therefore, RRC re-establishment is not triggered in the above two cases. In this case, the network device on the network side does not perform mobility robustness optimization and does not judge problems such as too late handover, too early handover and handover to a wrong cell in the previous two cases.

[0101] In application scenario 1 (mobility enhancement scenario), the embodiment of the present application provides a mobility optimization method to implement mobility robustness optimization by determining too late handover, too early handover and handover to a wrong cell in the mobility enhancement scenario and optimizing mobility parameters.

[0102] 2 is a first schematic flowchart of a mobility optimization method according to an embodiment of the present application. As shown in FIG. 2, the mobility optimization method provided in this embodiment of the present application includes, but is not limited to, the following steps:

[0103] S101: A first network device sends a handover message to a terminal device. In response, the terminal device receives the handover message.

[0104] In some possible implementations, the first network device may be a source base station. The handover message may be an RRC message, for example an RRC Connection Reconfiguration message carrying Mobility Control Info or an RRC Connection Reconfiguration message carrying reconfigurationWithSync. The handover message may be used to trigger the terminal device to perform a handover procedure from the source cell to the target cell. The handover procedure may include the following steps: (a) the terminal device synchronizes to the target cell but maintains a connection to the source cell (synchronizes to the target cell but maintains a connection with the source cell); (b) the target cell delivers an uplink allocation (UL allocation) and a timing advance for the terminal device (TA for the UE); (c) the terminal device sends an RRC Connection Reconfiguration Complete message to the target cell; and (d) the terminal device distinguishes PDCP packets from the source cell or the target cell (distinguishes PDCP packets from the source cell or the target cell). (e) The terminal device detaches from the source cell (Detach from Source Cell). (f) The target cell sends a UE context release message to the source cell. (g) The source cell releases resources (Release Resources). In this specification, in a handover procedure in which a terminal device is handed over from a source cell to a target cell, the terminal device still retains a radio connection to the source cell. That is, the terminal device can perform data communication in the source cell. In this embodiment of the present application, the target cell is the first cell and the source cell is the second cell. Optionally, the handover message may be a handover message delivered in a DAPS handover.

[0105] Optionally, in this specification, the terminal device maintaining a radio connection to the source cell may mean that the terminal device continues receiving downlink user data from the source cell until the terminal device releases the source cell, and the terminal device continues performing uplink data transmission in the source cell until the terminal device successfully completes a random access procedure in the target cell. Optionally, it has been previously determined that new uplink data is no longer transmitted in the source cell, and that uplink data transmitted by the terminal device to the source cell can still be retransmitted by the terminal device to the source cell.

[0106] In some possible implementations, the source cell and the target cell may be cells managed by the same network device. That is, both the source cell and the target cell are cells managed by a first network device. Alternatively, the source cell and the target cell may be cells managed by different network devices. For example, the source cell is a cell managed by a first network device, and the target cell is a cell managed by a second network device. This is not limited in this embodiment of the present application.

[0107] In some possible implementations, when the source cell is a cell managed by a first network device and the target cell is a cell managed by a second network device, before the first network device sends a handover message to the terminal device, the first network device may send a handover request to the second network device, and after receiving the handover request, the second network device may feed back a corresponding handover response message (handover request ACK) to the first network device.

[0108] S102: The terminal device sends connection failure information to the first network device. In response, the first network device receives the connection failure information.

[0109] In some possible implementations, the connection failure information may be used to indicate that the terminal device detects an RLF in the target cell (i.e., the first cell) or fails to be handed over to the target cell. Optionally, the connection failure information may include a signal quality of each cell (including the current target cell, the source cell, or another neighboring cell, etc.) detected by the terminal device. Optionally, the connection failure information may be handover failure information. For example, the failure information failureInformation message carries DAPS handover failure information. Optionally, the connection failure information is transmitted to the first network device through a wireless link between the terminal device and the first network device.

[0110] In some possible implementations, the handover message may carry one RRC re-establishment indication information. Alternatively, before the terminal device receives the handover message, the terminal device receives the RRC re-establishment indication information delivered by the first network device. The RRC re-establishment indication information may be used to indicate whether the terminal device performs RRC re-establishment after the terminal device detects RLF in the target cell or fails to be handed over to the target cell, and may be used to indicate that the terminal device does not perform RRC re-establishment after the terminal device detects RLF in the target cell or fails to be handed over to the target cell. Optionally, the RRC re-establishment indication information may be a condition for not performing RRC re-establishment after the terminal device detects RLF in the target cell or fails to be handed over to the target cell, for example, if the signal quality of the source cell is greater than a threshold, the terminal device does not perform RRC re-establishment. In this embodiment of the present application, if the terminal device does not perform RRC re-establishment, it sends connection failure information to the first network device.

[0111] S103: The first network device determines a connection failure type of the terminal device.

[0112] In some possible implementations, the connection failure type of the terminal device may include premature handover and handover to an incorrect cell. After the first network device receives the connection failure information, the first network device may determine the connection failure type of the terminal device. Specifically, if the first network device determines that the terminal device still holds a radio connection to the source cell after the terminal device detects an RLF in the target cell or fails to be handed over to the target cell (i.e., the first network device determines that the terminal device is camped on the source cell), the first network device determines that the connection failure type of the terminal device is premature handover. If the first network device determines that the third cell is the cell accessed by the terminal device (i.e., the first network device determines that the terminal device is handed over to a new target cell), the first network device determines that the connection failure type of the terminal device is handover to an incorrect cell. The third cell is different from the source cell (i.e., the second cell) and the target cell (i.e., the first cell). For example, if the source cell is cell A and the target cell is cell B, the third cell may be cell C. The connection failure type may be used for mobility robustness optimization. Optionally, the first network device may optimize mobility parameters after determining a premature handover or a handover to an incorrect cell. The mobility parameters may include one or more of a measurement filter coefficient, a corresponding measurement trigger threshold or period, a time to trigger or a hysteresis threshold, etc.

[0113] In some possible implementations, the first network device may determine an absolute difference between the sending time of the handover message and the receiving time of the connection failure information after determining that the terminal device still has a radio connection to the source cell. If the absolute difference is smaller than or equal to a first threshold (a set threshold), the first network device determines that the connection failure type of the terminal device is premature handover. Optionally, the first network device determines an absolute difference between the receiving time of the handover message reported by the terminal device and the time when the RLF is detected in the target cell (or the handover to the target cell fails). If the absolute difference is smaller than or equal to a first threshold (a set threshold), the first network device determines that the connection failure type of the terminal device is premature handover. Furthermore, optionally, if the absolute difference is smaller than or equal to the first threshold and the first network device determines that the handover message has been delivered to the terminal device recently, the first network device determines that the connection failure type of the terminal device is premature handover.

[0114] In some other possible implementations, the first network device may determine an absolute difference between the sending time of the handover message and the receiving time of the connection failure information after determining that the third cell is the cell accessed by the terminal device. If the absolute difference is smaller than or equal to a first threshold (a set threshold), the first network device determines that the connection failure type of the terminal device is handover to an incorrect cell. Optionally, the first network device determines an absolute difference between the receiving time of the handover message reported by the terminal device and the time when an RLF is detected in the target cell (or the handover to the target cell fails). If the absolute difference is smaller than or equal to a first threshold (a set threshold), the first network device determines that the connection failure type of the terminal device is premature handover. Furthermore, optionally, if the absolute difference is smaller than or equal to the first threshold and the first network device determines that the handover message has been delivered to the terminal device recently, the first network device determines that the connection failure type of the terminal device is handover to an incorrect cell.

[0115] In an optional implementation, the source cell is a cell managed by the first network device, and the target cell is a cell managed by the second network device. It can be understood that the first network device is a source base station, and the second network device is a target base station. After receiving the connection failure information, the first network device may transmit the connection failure information to the second network device. In response, the second network device receives the connection failure information. The first network device may further transmit the determined subsequent behavior of the terminal device (for example, the first network device determines that the terminal device continues to hold a radio connection to the source cell, or the first network device determines that the terminal device is handed over to a new target cell) to the second network device. The second network device determines a connection failure type of the terminal device.

[0116] Specifically, if the subsequent behavior of the terminal device received by the second network device is that the first network device determines that the terminal device continues to hold a radio connection to the source cell (i.e., determines that the terminal device is camped on the source cell), the second network device determines that the connection failure type of the terminal device is premature handover. Optionally, if the subsequent behavior of the terminal device received by the second network device is that the first network device determines that the terminal device continues to hold a radio connection to the source cell, and the second network device sends a handover response message to the first network device within a period before the second network device receives the connection failure information (or the second network device recognizes that the terminal device has previously been handed over from the source cell to the target cell), the second network device determines that the connection failure type of the terminal device is premature handover.

[0117] If the subsequent behavior of the terminal device received by the second network device indicates that the first network device determines that the terminal device is handed over to a new target cell, and the new target cell (e.g., cell C) is neither the source cell (e.g., cell A) nor the previous target cell (e.g., cell B), the second network device determines that the connection failure type of the terminal device is handover to an incorrect cell. Optionally, if the subsequent behavior of the terminal device received by the second network device is handover to a new target cell, and the second network device sends a handover response message to the first network device within a period before the second network device receives the connection failure information (or the second network device recognizes that the terminal device has been handed over from the source cell to the target cell before), the second network device determines that the connection failure type of the terminal device is handover to an incorrect cell.

[0118] It may be understood that after the first network device sends the connection failure information to the second network device, the first network device may not perform step S103 in FIG.

[0119] In some possible implementations, the second network device may send indication information to the first network device after determining that the connection failure type of the terminal device is premature handover or handover to a wrong cell. The indication information may be used to indicate that the connection failure type of the terminal device is premature handover or handover to a wrong cell. The first network device may optimize mobility parameters after receiving the indication information.

[0120] In this embodiment of the present application, after the terminal device detects an RLF in a target cell or fails to be handed over to the target cell, the terminal device sends connection failure information to the network side. The connection failure information is used to indicate that the terminal device detects an RLF in a target cell or fails to be handed over to the target cell. In response, a network device on the network side (which may be a first network device or a second network device) receives the connection failure information. The connection failure information may trigger the network device on the network side to determine a connection failure type (premature handover or handover to a wrong cell) of the terminal device. If the first network device determines that the terminal device is camped on the source cell, the first network device determines that the connection failure type of the terminal device is premature handover, or if the terminal device is handed over to a new target cell, the first network device determines that the connection failure type of the terminal device is handover to a wrong cell. The network device on the network side may optimize mobility parameters after determining the connection failure type of the terminal device. In this way, premature handover and handover to an incorrect cell are determined in a mobility enhancement scenario and mobility parameters are optimized, thereby implementing mobility robustness optimization.

[0121] 3 is a second schematic flowchart of a mobility optimization method according to an embodiment of the present application. As shown in FIG. 3, the mobility optimization method provided in this embodiment of the present application includes, but is not limited to, the following steps:

[0122] S201: A first network device sends a handover message to a terminal device. In response, the terminal device receives the handover message.

[0123] In some possible implementations, the implementation of step S201 in this embodiment of the present application may refer to the implementation of step S101 in the embodiment shown in Fig. 2. Details are not described again here.

[0124] S202: The terminal device sends connection failure information to the second network device. In response, the second network device receives the connection failure information.

[0125] S203: The second network device sends connection failure information to the first network device. In response, the first network device receives the connection failure information.

[0126] In some possible implementations, the connection failure information may be used to indicate that the terminal device detects an RLF in a source cell in a handover procedure from a source cell (i.e., a first cell) to a target cell (i.e., a second cell). In the handover procedure, before the terminal device detects an RLF in the source cell, the terminal device holds a radio connection to the source cell. If the terminal device detects an RLF in the source cell, the radio connection between the terminal device and the source cell is disconnected. That is, the terminal device cannot perform data communication in the source cell in this case. Optionally, the connection failure information may include a signal quality of each cell (including a current target cell, a source cell, or another neighboring cell, etc.) detected by the terminal device. The connection failure information may be, for example, an RLF indication information carried in a failure information failureInformation message. Optionally, the connection failure information is transmitted to the second network device through a radio link between the terminal device and the second network device.

[0127] It can be understood that when the source cell and the target cell are cells managed by different network devices, the first network device may be a source base station, the source cell is a cell managed by the first network device, the second network device may be a target base station, and the target cell is a cell managed by the second network device. When the terminal device detects an RLF in the source cell in a handover procedure from the source cell to the target cell, the terminal device may record connection failure information for the source cell (i.e., the RLF information detected in the source cell). After the terminal device successfully performs a random access procedure in the target cell (i.e., the terminal device is successfully handed over to the target cell to perform data communication), the terminal device may transmit the recorded connection failure information to the second network device. In response, the second network device receives the connection failure information. After receiving the connection failure information, the second network device may transmit the connection failure information to the first network device. In response, the first network device receives the connection failure information.

[0128] In some possible implementations, the manner in which the terminal device records the connection failure information for the source cell may be as follows: The terminal device records only the latest RLF or handover failure to the target cell. That is, each time a failure of an RLF or handover to the target cell is detected, only the currently detected RLF or handover failure to the target cell is recorded, and the previous record is overwritten. Optionally, the failure type carried in the connection failure information reported by the terminal device to the second network device in the mobility enhancement scenario may indicate the RLF in the source cell in the handover procedure in the mobility enhancement. Alternatively, the terminal device reports the RLF separately and independently. That is, in the handover procedure in the mobility enhancement, the RLF detected in the source cell and another detected RLF record are reported independently and are not overwritten each other.

[0129] It may be further understood that when the source cell and the target cell are cells managed by the same network device, the first network device may be a source base station, both the source cell and the target cell are cells managed by the first network device, and the first network device and the second network device are the same physical device. When the terminal device detects an RLF in the source cell in a handover procedure from the source cell to the target cell, the terminal device may record connection failure information for the source cell (i.e., the RLF information detected in the source cell). After the terminal device successfully executes a random access procedure in the target cell (i.e., the terminal device is successfully handed over to the target cell to perform data communication), the terminal device may transmit the recorded connection failure information to the first network device.

[0130] S204: The first network device determines a connection failure type of the terminal device.

[0131] In some possible implementations, the connection failure type may include a handover that is too late. Specifically, if the first network device determines that the time that the terminal device camps on the source cell is greater than a second threshold (i.e., the first network device determines that the time that the terminal device camps on the source cell is too long) and the terminal device successfully accesses the target cell, the first network device determines that the connection failure type of the terminal device is a handover that is too late. The connection failure type may be used for mobility robustness optimization. Optionally, the first network device may optimize mobility parameters after determining a handover that is too late. The mobility parameters may include one or more of a measurement filter coefficient, a corresponding measurement trigger threshold or period, a time to trigger or a hysteresis threshold, etc. The second threshold may be determined based on a time that the signal quality of the source cell detected by the terminal device before the terminal device receives a handover message is lower than the signal quality of another cell (which may be the target cell during handover or another neighboring cell).

[0132] In this application, the time when the terminal device is camped on the source cell is the time when the terminal device holds an RRC connection to the source cell, or the time when the terminal device holds a radio connection to the source cell, or the time when the terminal device has a connection to the source cell but has not received a handover command. The time when the terminal device is camped on a specific cell in other parts of this application has the same meaning. Details will not be described again.

[0133] In this embodiment of the present application, after the terminal device detects the RLF in the source cell in the procedure of handover from the source cell to the target cell, the terminal device records the RLF information detected in the source cell (i.e., connection failure information). After the terminal device successfully accesses the target cell, the terminal device sends the recorded connection failure information to the second network device. The connection failure information is used to indicate that the terminal device detects the RLF in the source cell in the procedure of handover from the source cell to the target cell. After the second network device receives the connection failure information, the second network device forwards the connection failure information to the first network device. The connection failure information may trigger the first network device to determine the connection failure type (too late handover) of the terminal device. If the first network device determines that the terminal device camps on the source cell for an excessively long time and the terminal device successfully accesses the target cell, the first network device determines that the connection failure type of the terminal device is too late handover. After determining the connection failure type of the terminal device, the first network device may optimize mobility parameters. Optionally, the second network device may determine the connection failure type. For example, if the second network device sends a handover response message to the first network device within a period before the second network device receives the connection failure information (or the second network device recognizes that the terminal device has been handed over from the source cell to the target cell before), the second network device determines that the connection failure type of the terminal device is a too late handover. In this way, the too late handover is determined in a mobility enhancement scenario, and the mobility parameters are optimized, thereby implementing the mobility robustness optimization.

[0134] [Scenario 2: Dual Connectivity]

[0135] In the MR-DC enhancement in Release R16, a terminal device is simultaneously connected to two network devices, also referred to as nodes (MN and SN). When the terminal device detects an RLF in an MCG (master cell group managed by the MN), the terminal device may send one MCG failure information to the MN by using the SN. Specifically, the terminal device first sends the MCG failure information to the SN, and then the SN forwards the MCG failure information to the MN. Optionally, the MCG failure information may be carried by using an RRC message of the SN, e.g., signaling radio bearer 3 (SRB3). The SRB3 is a direct SRB between the terminal device and the SN. Alternatively, the MCG failure information may be sent by using a branch of an SRB of the MCG on the SN side, e.g., split signaling radio bearer 1 (split SRB1). The split SRB is an SRB between the MN and the terminal device, and the SRB has an RLC bearer in each of the MCG and the SCG (secondary cell group).

[0136] When the terminal device detects an RLF in the MCG, the terminal device still has a radio connection to the SCG. Therefore, when the terminal device detects an RLF in the MCG, RRC re-establishment is not triggered. When an RLF is detected in the MCG in a dual connectivity scenario, mobility robustness optimization is not performed on the network side, and handovers that are too late, too early, and to the wrong cell are not determined.

[0137] In application scenario 2 (RLF in MCG in dual connectivity scenario), the embodiment of the present application provides a mobility optimization method to determine too late handover, too early handover and handover to a wrong cell after RLF in MCG is detected, and to implement mobility robustness optimization by optimizing mobility parameters.

[0138] 4 is a third schematic flowchart of a mobility optimization method according to an embodiment of the present application. As shown in FIG. 4, the mobility optimization method provided in this embodiment of the present application includes, but is not limited to, the following steps:

[0139] S301: A terminal device sends connection failure information to a second network device. In response, the second network device receives the connection failure information.

[0140] S302: The second network device sends connection failure information to the first network device. In response, the first network device receives the connection failure information.

[0141] In some possible implementations, the connection failure information may be used to indicate that the terminal device has detected an RLF in an MCG managed by the first network device.

[0142] In some possible implementations, a network device (e.g., a terminal device, e.g., a master network device of a first network device, or a network device to which a UE is connected before being handed over to the first network device) may send configuration information for fast MCG failure recovery to the terminal device. After the terminal device receives the configuration information for fast MCG failure recovery, if the terminal device detects an RLF in the MCG, the terminal device may perform fast MCG failure recovery. For example, the terminal device performs fast MCG failure recovery by using a second network device (i.e., a secondary network device SN). Specifically, the terminal device may send connection failure information to the second network device. In response, the second network device receives the connection failure information. After receiving the connection failure information, the second network device may forward the connection failure information to the first network device. In response, the first network device receives the connection failure information.

[0143] S303: The first network device determines a connection failure type of the terminal device.

[0144] In some possible implementations, the first network device is a source master network device, i.e., a source MN, and the second network device is a secondary network device, SN. The connection failure type includes a too late handover. After receiving the connection failure information, the first network device may determine whether the connection failure type of the terminal device is a too late handover. Specifically, when the first network device determines that the fourth cell is the cell accessed by the terminal device (i.e., the first network device determines that the primary cell PCell of the terminal device has changed to a new cell different from the primary cell in the MCG managed by the first network device, e.g., the first network device has determined that the primary cell PCell of the terminal device has changed from cell A to cell D), the first network device determines that the connection failure type of the terminal device is a too late handover. The fourth cell is different from the primary cell in the MCG managed by the first network device. For example, the primary cell in the MCG managed by the first network device may be cell A, and the fourth cell may be cell D. Optionally, the fourth cell may be a secondary cell SCell managed by the first network device. Optionally, the first network device may optimize mobility parameters after determining the handover is too late. The mobility parameters may include one or more of a measurement filter coefficient, a corresponding measurement trigger threshold or period, a time to trigger or a hysteresis threshold, etc.

[0145] Optionally, if the fourth cell is a cell accessed by the terminal device and the first network device determines that the time that the terminal device is camped on the primary cell in the MCG managed by the first network device is greater than a third threshold (i.e., the first network device determines that the time that the terminal device is camped on the primary cell in the MCG managed by the first network device is excessively long), the first network device determines that the connection failure type of the terminal device is a too-late handover.

[0146] Optionally, if the first network device determines that the fourth cell is a cell accessed by the terminal device, and the first network device has not sent a handover message to the terminal device within a period before the connection failure information is received, the first network device determines that the connection failure type of the terminal device is a too late handover.

[0147] In some possible implementations, the first network device is a target master network device, i.e., a target MN, and the second network device is a secondary network device, SN. The connection failure type may include premature handover or handover to an incorrect cell. The first network device may determine the connection failure type of the terminal device after receiving the connection failure information. Specifically, when the first network device determines that the source master network device (e.g., the first network device, or the network device to which the UE is connected before being handed over to the first network device) has recently sent a handover message to the terminal device, which is used to indicate that the primary cell has changed (e.g., the primary cell has changed from cell A to cell B), and determines that the fifth cell (e.g., cell A) is the cell accessed by the terminal device (i.e., the terminal device is camped on the unchanged primary cell, e.g., cell A), the first network device determines that the connection failure type of the terminal device is premature handover. The fifth cell is a cell accessed before the primary cell in the MCG managed by the first network device is handed over. For example, the fifth cell is cell A, the primary cell in the MCG managed by the first network device is cell B, and the handover message is used to indicate that the primary cell of the terminal device is changing from cell A to cell B.

[0148] If the first network device (i.e., the target master network device) determines that the source master network device (e.g., the first network device or a network device to which the UE is connected before being handed over to the first network device) has recently sent a handover message to the terminal device used to indicate that the primary cell has changed (e.g., the primary cell has changed from cell A to cell B) and determines that the sixth cell (e.g., cell C) is the cell accessed by the terminal device (i.e., determines that the terminal device has been handed over to a new primary cell, which is different from cells A and B), the first network device determines that the connection failure type of the terminal device is handover to an incorrect cell. The sixth cell is different from the primary cell and the fifth cell in the MCG managed by the first network device. For example, the fifth cell may be cell A, the primary cell in the MCG managed by the first network device may be cell B, and the sixth cell may be cell C, and the handover message is used to indicate that the primary cell of the terminal device is changing from cell A to cell B.

[0149] The fifth cell (e.g., cell A) and the primary cell (e.g., cell B) in the MCG managed by the first network device may be cells managed by the same master network device (MN). That is, the source master network device and the first network device are the same physical device. The fifth cell (e.g., cell A) and the primary cell (e.g., cell B) in the MCG managed by the first network device may alternatively be cells managed by different master network devices (MN). That is, the source master network device and the first network device are different physical devices, and the fifth cell is a cell managed by the source master network device or a primary cell managed by the source master network device.

[0150] In some possible implementations, when the source master network device and the first network device are different physical devices and the first network device is a target master network device, the first network device may send second indication information to the source master network device after determining that the connection failure type of the terminal device is premature handover or handover to a wrong cell. The second indication information may be used to indicate that the connection failure type of the terminal device is premature handover or handover to a wrong cell. Optionally, the source master network device may optimize mobility parameters after determining that the received connection failure type is premature handover or handover to a wrong cell. The mobility parameters may include one or more of a measurement filter coefficient, a corresponding measurement trigger threshold or period, a time to trigger or a hysteresis threshold, etc.

[0151] In this embodiment of the present application, after the terminal device detects the RLF in the MCG, it sends connection failure information to the secondary network device (the second network device), and the secondary network device forwards the connection failure information to the first network device (which may be the source master network device or the target master network device). The connection failure information is used to indicate that the terminal device detects the RLF in the MCG. The connection failure information may trigger the first network device to determine the connection failure type of the terminal device (handover too late, handover too early, or handover to a wrong cell). If the first network device determines that the primary cell PCell of the terminal device has changed to a new cell, the first network device determines that the connection failure type of the terminal device is handover too late. If the first network device determines that the source master network device has recently sent a handover message to the terminal device, which is used to indicate that the primary cell has changed, and the terminal device is camped on the unchanged primary cell, the first network device determines that the connection failure type of the terminal device is handover too early. If the first network device determines that the source master network device has recently sent a handover message to the terminal device, which is used to indicate that the primary cell has changed, and determines that the terminal device has been handed over to the new primary cell, the first network device determines that the connection failure type of the terminal device is a handover to an incorrect cell. After the connection failure type of the terminal device is determined on the network side, the mobility parameters can be optimized. In this way, the handover that is too late, the handover that is too early, and the handover to an incorrect cell are determined in the dual connectivity scenario, and the mobility parameters are optimized, thereby implementing the mobility robustness optimization.

[0152] [Scenario 3: Conditional Handover (CHO)]

[0153] In CHO, if the quality of the source link is good, the network device corresponding to the source cell sends CHO configuration information to the terminal device. The CHO configuration information may include a CHO trigger condition and information about one or more candidate cells. The information about the candidate cell may include an identifier of the candidate cell and frequency information corresponding to the candidate cell. The identifier of the candidate cell may be a cell global identifier (CGI) of the candidate cell or a physical cell identifier (PCI) of the candidate cell. After receiving the CHO configuration information, the terminal device determines whether one or more candidate cells meet the CHO trigger condition based on the CHO configuration information, and uses a specific candidate cell that meets the CHO trigger condition as a target cell. Then, the terminal device performs a random access procedure in the determined target cell. If the terminal device successfully performs the random access in the target cell, it sends an RRC message (e.g., an RRC reconfiguration complete message) to the target cell to notify that the conditional handover to the target cell is completed.

[0154] Therefore, in the CHO scenario, if a certain candidate cell satisfies the CHO triggering condition, the terminal device directly accesses the candidate cell that satisfies the CHO triggering condition, and does not need to perform RRC re-establishment. In this case, no mobility robustness optimization is performed on the network side, and handover that is too late, too early and to a wrong cell is not determined.

[0155] In application scenario 3 (RRC re-establishment is not performed in conditional scenario), the embodiment of the present application provides a mobility optimization method to implement mobility robustness optimization by determining too late handover, too early handover and handover to a wrong cell in mobility enhancement scenario and optimizing mobility parameters when RRC re-establishment is not performed in conditional inter-cell handover scenario.

[0156] 5 is a fourth schematic flowchart of a mobility optimization method according to an embodiment of the present application. As shown in FIG. 5, the mobility optimization method provided in this embodiment of the present application includes, but is not limited to, the following steps:

[0157] S401: A first network device sends CHO configuration information to a terminal device. In response, the terminal device receives the CHO configuration information.

[0158] In some possible implementations, the CHO configuration information may include a CHO trigger condition and information about one or more candidate cells. The information about the candidate cells may include an identifier of the candidate cell and frequency information corresponding to the candidate cell. The identifier of the candidate cell may be a CGI or a PCI.

[0159] S402: The terminal device sends connection failure information to the second network device. In response, the second network device receives the connection failure information.

[0160] S403: The second network device sends connection failure information to the first network device. In response, the first network device receives the connection failure information.

[0161] In some possible implementations, the connection failure information may be used to indicate that the terminal device detects RLF in the source cell. It may be understood that the first network device is a source base station and the second network device is a target base station. The source cell is a cell managed by the first network device. The target cell is a cell managed by the second network device. In this embodiment of the present application, the source cell is the first cell and the target cell is the second cell. The target cell is a candidate cell among one or more candidate cells that satisfies the CHO trigger condition or the first condition. Alternatively, the target cell is a cell obtained through cell reselection by the terminal device.

[0162] In some possible implementations, when the terminal device detects an RLF in the source cell, it may record the RLF information detected in the source cell (i.e., connection failure information) and may detect the signal quality of each of one or more candidate cells. When the terminal device detects that the signal quality of a candidate cell i among these candidate cells satisfies the CHO trigger condition or satisfies the first condition, it may perform random access in the candidate cell i. For example, the CHO trigger condition or the first condition is that the signal quality is higher than a threshold. In this case, if the signal quality of the candidate cell i is higher than the threshold, the terminal device performs random access in the candidate cell i. The candidate cell i may be referred to as a target cell. The target cell may be a cell managed by a second network device. After the terminal device successfully performs random access in the target cell (i.e., the candidate cell i), the terminal device may send connection failure information to the second network device. In response, the second network device receives the connection failure information. After receiving the connection failure information, the second network device may forward the connection failure information to the first network device. In response, the first network device receives the connection failure information. Optionally, the first condition may be carried in the CHO configuration information.

[0163] In some possible implementations, when the terminal device detects an RLF in the source cell, it may record the RLF information detected in the source cell (i.e., connection failure information), start a timer, and simultaneously detect the signal quality of each of the one or more candidate cells. If the terminal device does not detect that the signal quality of any candidate cell meets the CHO trigger condition or the first condition after the timer expires, the terminal device may perform cell reselection. If the cell acquired through cell reselection by the terminal device is a candidate cell j among the one or more candidate cells, the terminal device performs random access in the candidate cell j acquired through cell reselection. The candidate cell j may be referred to as a target cell. The target cell may be a cell managed by the second network device. After the terminal device successfully performs random access in the target cell (i.e., the candidate cell j), the terminal device may send connection failure information to the second network device. In response, the second network device receives the connection failure information. After receiving the connection failure information, the second network device may forward the connection failure information to the first network device. In response, the first network device receives the connection failure information.

[0164] S404: The first network device determines a connection failure type of the terminal device.

[0165] In some possible implementations, the connection failure type of the terminal device may include a handover that is too late. Specifically, if the first network device determines that the time that the terminal device camps on the source cell is greater than a second threshold (i.e., the first network device determines that the time that the terminal device camps on the source cell is too long), and the terminal device successfully accesses the target cell, the first network device determines that the connection failure type of the terminal device is a handover that is too late. The connection failure type may be used for mobility robustness optimization. Optionally, the first network device may optimize mobility parameters after determining a handover that is too late. The mobility parameters may include one or more of a measurement filter coefficient, a corresponding measurement trigger threshold or period, a time to trigger or a hysteresis threshold, etc.

[0166] In this embodiment of the present application, after the terminal device detects the RLF in the source cell, it records the RLF information (i.e., connection failure information) detected in the source cell. After the terminal device successfully accesses the target cell (candidate cell) that satisfies the CHO trigger condition, the terminal device sends the recorded connection failure information to the second network device, and the second network device forwards the connection failure information to the first network device. The connection failure information is used to indicate that the terminal device detects the RLF in the source cell. The connection failure information may trigger the first network device to determine the connection failure type (too late handover) of the terminal device. If the first network device determines that the terminal device camps on the source cell for an excessively long time and the terminal device successfully accesses the target cell, the first network device determines that the connection failure type of the terminal device is too late handover. The first network device may optimize mobility parameters after determining the connection failure type of the terminal device. In this way, if RRC re-establishment is not performed in the CHO scenario, a handover that is too late is determined and the mobility parameters are optimized, thereby implementing mobility robustness optimization.

[0167] 6 is a fifth schematic flowchart of a mobility optimization method according to an embodiment of the present application. As shown in FIG. 6, the mobility optimization method provided in this embodiment of the present application includes, but is not limited to, the following steps:

[0168] S501: A first network device sends CHO configuration information to a terminal device. In response, the terminal device receives the CHO configuration information.

[0169] In some possible implementations, the implementation of step S501 in this embodiment of the present application may refer to the implementation of step S401 in the embodiment shown in Fig. 5. Details are not described again here.

[0170] S502: When the terminal device fails to be handed over from the first cell to the second cell, the terminal device re-accesses the first cell.

[0171] In some possible implementations, the first cell is a source cell, and the second cell is a target cell. If the terminal device detects that a candidate cell i among one or more candidate cells satisfies the CHO trigger condition, the terminal device performs random access in the candidate cell i. The candidate cell i may be referred to as a target cell. The terminal device has a radio connection to the source cell in a random access procedure (handover procedure to the target cell) in the target cell (candidate cell i). Having a radio connection in this specification means that the terminal device holds a connection configuration in the source cell, but the terminal device cannot perform data communication in the source cell. If the terminal device fails to perform random access in the target cell (candidate cell i) (i.e., fails to be handed over to the target cell), the terminal device performs a rollback to data communication in the source cell. That is, the terminal device re-accesses the source cell. Optionally, the terminal device may record random access failure information in the target cell.

[0172] In some possible implementations, before the terminal device detects a candidate cell i among the candidate cells that satisfies the CHO trigger condition, the terminal device may receive first indication information transmitted by a first network device. The first indication information may be used to indicate to the terminal device to access the source cell (i.e., perform a rollback to data communication in the source cell) after the terminal device fails to perform random access in the target cell (i.e., fails to be handed over to the target cell). Optionally, the first indication information may be used to indicate a rollback condition. If the terminal device detects that the signal quality of the source cell satisfies the rollback condition after the terminal device fails to perform random access in the target cell, the terminal device re-accesses the source cell. For example, the rollback condition may be that the signal quality is higher than a threshold. That is, if the terminal device detects that the signal quality of the source cell is higher than a threshold after the terminal device fails to perform random access in the target cell, the terminal device re-accesses the source cell.

[0173] S503: The terminal device sends connection failure information to the first network device. In response, the first network device receives the connection failure information.

[0174] In some possible implementations, the connection failure information may be used to indicate that the terminal device fails to be handed over to the target cell (i.e., fails to perform random access in the target cell). It may be understood that the random access failure information in the target cell is connection failure information. The first network device is a source base station. The source cell is a cell managed by the first network device.

[0175] S504: The first network device determines a connection failure type of the terminal device.

[0176] In some possible implementations, the connection failure type may include premature handover or handover to an incorrect cell. After the first network device receives the connection failure information, the first network device may determine the connection failure type of the terminal device. Specifically, if the first network device determines that the terminal device continues to hold a radio connection to the source cell (i.e., the second cell) after the terminal device successfully re-accesses the source cell (i.e., the first network device determines that the terminal device is camped on the source cell), the first network device determines that the connection failure type of the terminal device is premature handover. If the first network device determines that the third cell is the cell accessed by the terminal device (i.e., the first network device determines that the terminal device is handed over to a new target cell), the first network device determines that the connection failure type of the terminal device is handover to an incorrect cell. The third cell is different from any one of the source cell (i.e., the first cell) and one or more candidate cells. The connection failure type may be used for mobility robustness optimization. Optionally, the first network device may optimize mobility parameters after determining a premature handover or a handover to an incorrect cell. The mobility parameters may include one or more of a measurement filter coefficient, a corresponding measurement trigger threshold or period, a time to trigger or a hysteresis threshold, etc.

[0177] In some possible implementations, the first network device may determine an absolute difference between the transmission time of the CHO configuration information and the reception time of the connection failure information after determining that the terminal device continues to hold a radio connection to the source cell after the terminal device successfully re-accesses the source cell. If the absolute difference is smaller than or equal to a set threshold, the first network device determines that the connection failure type of the terminal device is premature handover. Optionally, the absolute difference may alternatively be an absolute difference between the reception time of the CHO configuration information reported by the terminal device and the time when the handover to the target cell fails (i.e., the random access in the target cell fails). Furthermore, optionally, if the absolute difference is smaller than or equal to a set threshold and the first network device determines that the CHO configuration information has been recently delivered to the terminal device, the first network device determines that the connection failure type of the terminal device is premature handover.

[0178] In some other possible implementations, the first network device may determine an absolute difference between the sending time of the CHO configuration information and the receiving time of the connection failure information after determining that the third cell is the cell accessed by the terminal device. If the absolute difference is smaller than or equal to a set threshold, the first network device determines that the connection failure type of the terminal device is handover to an incorrect cell. Optionally, the absolute difference may alternatively be the absolute difference between the receiving time of the CHO configuration information reported by the terminal device and the time when the handover to the target cell fails (i.e., the random access in the target cell fails). Furthermore, optionally, if the absolute difference is smaller than or equal to a set threshold and the first network device determines that the CHO configuration information has been recently delivered to the terminal device, the first network device determines that the connection failure type of the terminal device is handover to an incorrect cell.

[0179] In an optional embodiment, step S502 may be replaced by step S502': if the terminal device fails to be handed over from the first cell to the second cell, the terminal device determines a signal quality of another cell and selects a cell from the other cells for access. For example, the terminal device determines a signal quality of another candidate cell and / or the first cell, and if the signal quality of a particular cell is higher than a threshold, the terminal device accesses this cell. Optionally, the threshold is carried in the CHO configuration information.

[0180] It can be understood that step S503 can alternatively be replaced by step S503': the terminal device sends connection failure information to a third network device corresponding to the successfully accessed cell. In response, the third network device receives the connection failure information. If the successfully accessed cell is the first cell, the connection failure type of the terminal device is determined according to the method in step S504.

[0181] In this embodiment of the present application, after the terminal device fails to perform random access in the target cell (candidate cell) (i.e. fails to be handed over to the target cell), the terminal device re-accesses the source cell and records random access failure information in the target cell (i.e. connection failure information). After the terminal device successfully accesses the source cell, the terminal device sends connection failure information to a network device (first network device) on the network side. The connection failure information is used to indicate that the terminal device fails to be handed over to the target cell. The connection failure information may trigger the first network device to determine the connection failure type of the terminal device (premature handover or handover to a wrong cell). If the first network device determines that the terminal device is camped on the source cell, the first network device determines that the connection failure type of the terminal device is premature handover. If the first network device determines that the terminal device is handed over to a new target cell, the first network device determines that the connection failure type of the terminal device is handover to a wrong cell. The first network device may optimize the mobility parameters after determining the connection failure type of the terminal device. In this way, premature handover and handover to an incorrect cell are determined when RRC re-establishment is not performed in the CHO scenario, and the mobility parameters are optimized, thereby implementing mobility robustness optimization.

[0182] An embodiment of the present application further provides a mobility optimization method for different radio access technologies (RATs). The method can be used to determine handover too late, handover too early, and handover to a wrong cell. The mobility optimization method for different RATs may be applied to handover of a UE between different radio access technologies in the same system (e.g., handover of a UE between an ng-eNB and a gNB), and may also be applied to handover of a UE between different radio access technologies in different systems (e.g., handover of a UE between an eNB and a gNB). Figure 7 is a schematic flowchart of a mobility optimization method for different RATs according to an embodiment of the present application. As shown in Figure 7, the mobility optimization method for different RATs includes, but is not limited to, the following steps:

[0183] S601: A UE fails to be handed over from a first cell in a first RAT to a second cell in a second RAT, or the UE detects an RLF in the second cell in the second RAT shortly after the UE is successfully handed over from the first cell in the first RAT to the second cell, or the UE detects an RLF in the first cell in the first RAT.

[0184] In some possible implementations, when the UE is handed over from a first cell (e.g., cell 1) of a first RAT to a second cell (e.g., cell 2) of a second RAT, a handover failure occurs when the UE is handed over to the second cell of the second RAT (usually, when the UE receives a handover message, the UE starts a timer, and when the timer expires, the UE has not completed the handover to the second cell of the second RAT or has not successfully completed the random access procedure in the second cell of the second RAT), and the UE records connection failure information. Such a failure is referred to as handover failure. That is, the failure type is handover failure (HOF). The UE performs an RRC re-establishment procedure (the UE performs cell selection in the re-establishment procedure), and the UE includes an identifier of a cell obtained through cell selection by the UE in the connection failure information. The identifier of a cell in this application may be a cell global identifier of the cell, a physical cell identifier of the cell, or a physical cell identifier and a frequency of the cell.

[0185] In some possible implementations, after the UE is successfully handed over from a first cell (e.g., cell 1) of a first RAT to a second cell (e.g., cell 2) of a second RAT, the UE immediately undergoes an RLF in the second cell (e.g., cell 2). In this case, the UE records connection failure information. The UE further records information about the first cell (e.g., cell 1) and / or the second cell (e.g., cell 2) in the connection failure information. Such a failure is caused by an RLF. That is, the failure type is an RLF. The UE performs an RRC re-establishment procedure (the UE performs cell selection in the re-establishment procedure), and the UE includes an identifier of a cell obtained through cell selection by the UE in the connection failure information.

[0186] S602: The UE performs a radio connection access in a third cell of the second RAT, and sends connection failure information to the third cell (eg, cell 3) of the second RAT.

[0187] In some possible implementations, the UE may transmit connection failure information in the cell obtained through cell selection after performing RRC re-establishment after step S601. Alternatively, after the UE performs RRC re-establishment after step S601, the UE may perform radio connection access in another cell of the second RAT after the RRC re-establishment fails in the cell obtained through cell selection, and transmit connection failure information to the cell in which the radio connection access is performed.

[0188] Optionally, the connection failure information may be carried in the RRC message of the second RAT in the form of a container. Optionally, in addition to the content carried in the container, the UE needs to additionally include, outside the container, an identifier of the serving cell to which the previous handover has failed (e.g., if the handover from cell 1 to cell 2 fails, the identifier of cell 2 is carried; if the handover from cell 1 to cell 2 is successful but an RLF occurs immediately in cell 2, the identifier of cell 2 is carried; or if an RLF is detected in cell 1, the identifier of cell 1 is carried). Optionally, the UE may further include, outside the container, a tracking area code (TAC) of the serving cell. A network device (e.g., a base station corresponding to a third cell of the second RAT) may receive the connection failure information in the form of a container, and perform routing based on the identifier of the serving cell, or based on the identifier of the serving cell and the tracking area code of the serving cell, to send the connection failure information to the base station to which the serving cell belongs. In another possible implementation, if the failure type is HOF, the identifier of the serving cell where the previous handover has failed, carried outside the container, is the identifier of the cell where the terminal device receives the reconfiguration message or handover command message, i.e., the identifier of the cell accessed before the reconfiguration message or handover command message is received. If the failure type is RLF, the identifier of the serving cell where the previous handover has failed, carried outside the container, is the identifier of the cell where the connection failure occurs. For example, if the handover from cell 1 to cell 2 has failed, i.e., the failure type is HOF, the identifier of cell 1 is carried outside the container. Optionally, the TAC of cell 1 may further be carried outside the container. If the handover from cell 1 to cell 2 is successful, but an RLF occurs immediately in cell 2, the identifier of cell 2 is carried outside the container. Optionally, the TAC of cell 2 may further be carried outside the container, and if an RLF is detected in cell 1, the identifier of cell 1 is carried outside the container. Optionally, the TAC of cell 1 may also be transported outside the container.

[0189] Optionally, the UE may include the type information of the serving cell outside the container. For example, the type information of the serving cell indicates that the serving cell is an LTE cell, an eLTE cell, or an NR cell. For example, the type information of the serving cell is one of LTE, eLTE, or NR. LTE means that the UE is connected to a 4G core network by using an E-UTRAN radio access technology. eLTE means that the UE is connected to a 5G core network by using an E-UTRAN radio access technology. NR means that the UE is connected to a 5G core network by using an NR radio access technology.

[0190] Optionally, in a possible implementation, for example, in a predefined manner in the protocol, it may be predefined in the protocol that the coding format or RRC format of the connection failure information may be the same as that for the type of the serving cell. For example, if the serving cell is an LTE cell, the corresponding CGI is the CGI of the LTE cell, and the connection failure information in the container is encoded in the LTE RRC format. In another possible implementation, the coding format of the connection failure information is independent of the type of the serving cell.

[0191] S603: The third cell of the second RAT sends connection failure information to the second cell of the second RAT or the first cell of the first RAT.

[0192] In some possible implementations, the third cell of the second RAT (e.g., cell 3) transmits the connection failure information received from the UE to the second cell (e.g., cell 2). The third cell of the second RAT may transmit the connection failure information to the base station corresponding to the second cell over the core network (i.e., the connection failure information is first transmitted to the core network, and then the core network forwards the connection failure information to the base station corresponding to the second cell). The third cell of the second RAT may alternatively transmit the connection failure information to the base station corresponding to the second cell through an interface between base stations (e.g., an Xn interface). The connection failure information may alternatively be transmitted in the form of a container to the base station corresponding to the second cell. Optionally, when the third cell of the second RAT sends the connection failure information to the second cell, an RRC format corresponding to the specific RAT used by the connection failure information, or an RRC format of the specific RAT in which the connection failure information is encoded, or an RRC format of the specific RAT in which the UE performs encoding, such as an LTE format or an NR format, or an LTE format, an NR format, or an eLTE format, is additionally carried. The LTE format is the RRC format of the radio air interface when the UE is connected to the 4G core network by using the E-UTRAN radio access technology. The eLTE format is the RRC format of the radio air interface when the UE is connected to the 5G core network by using the E-UTRAN radio access technology. The NR format is the RRC format of the radio air interface when the UE is connected to the 5G core network by using the NR radio access technology. Optionally, in a possible implementation, the third cell of the second RAT receives, from the UE, type information reported by the UE of a serving cell to which the UE has failed to be handed over, and determines, based on the type information of the serving cell, an RRC format corresponding to the specific RAT used by the connection failure information, or an RRC format of the specific RAT in which the connection failure information is encoded, or an RRC format of the specific RAT in which the UE performs the encoding.For example, it is predefined in the protocol that the coding format or RRC format of the connection failure information may be the same as that for the type of the serving cell in a predefined manner in the protocol. The third cell of the second RAT may determine the RRC format corresponding to the specific RAT used by the connection failure information, or the RRC format of the specific RAT in which the connection failure information is encoded, or the RRC format of the specific RAT in which the UE performs encoding based on the type information of the serving cell.

[0193] Optionally, when the third cell of the second RAT sends the connection failure information to the second cell, it additionally includes an identifier reported by the UE of the serving cell to which the UE is unsuccessfully handed over (e.g., if the handover from cell 1 to cell 2 fails, the identifier of cell 2 is carried, or if the handover from cell 1 to cell 2 is successful but an RLF immediately occurs in cell 2, the identifier of cell 2 is carried, or, for example, if the handover from cell 1 to cell 2 fails, i.e., the failure type is HOF, the identifier of cell 1 is carried, or if the handover from cell 1 to cell 2 is successful but an RLF immediately occurs in cell 2, the identifier of cell 2 is carried). Optionally, when the third cell of the second RAT sends the connection failure information to the second cell, it additionally includes a tracking area code (TAC) reported by the UE of the serving cell to which the UE is unsuccessfully handed over. Specifically, for the description of the identifier reported by the UE of the serving cell to which the UE is unsuccessfully handed over and the tracking area code of the serving cell, please refer to the description in S602.

[0194] The base station serving the second cell determines whether the previous handover was a premature handover or a handover to a wrong cell.

[0195] In some possible implementations, the third cell of the second RAT (e.g., cell 3) transmits the connection failure information received from the UE to the first cell (e.g., cell 1). The third cell of the second RAT may transmit the connection failure information to the base station corresponding to the first cell over the core network (i.e., the connection failure information is first transmitted to the core network, and then the core network forwards the connection failure information to the base station corresponding to the first cell). The third cell of the second RAT may alternatively transmit the connection failure information to the base station corresponding to the first cell through an interface between base stations (e.g., an Xn interface). The connection failure information may alternatively be transmitted in the form of a container to the base station corresponding to the first cell. Optionally, when the third cell of the second RAT sends the connection failure information to the first cell, an RRC format corresponding to the specific RAT used by the connection failure information, or an RRC format of the specific RAT in which the connection failure information is encoded, or an RRC format of the specific RAT in which the UE performs encoding, such as an LTE format or an NR format, or an LTE format, an NR format, or an eLTE format, is additionally carried. The LTE format is the RRC format of the radio air interface when the UE is connected to the 4G core network by using the E-UTRAN radio access technology. The eLTE format is the RRC format of the radio air interface when the UE is connected to the 5G core network by using the E-UTRAN radio access technology. The NR format is the RRC format of the radio air interface when the UE is connected to the 5G core network by using the NR radio access technology. Optionally, when the third cell of the second RAT sends connection failure information to the first cell (for example, the third cell sends connection failure information to the core network), the identifier reported by the UE of the serving cell to which the UE is unsuccessfully handed over is additionally carried. Optionally, the TAC of the serving cell may be further carried. For the description of the identifier and TAC of the serving cell to which the UE is unsuccessfully handed over, please refer to the description in S602. Details will not be described again here.The base station corresponding to the first cell determines whether the previous handover is a too late handover or a handover to a wrong cell.

[0196] S604: The second cell of the second RAT sends connection failure information to the first cell of the first RAT.

[0197] In some possible implementations, after the base station corresponding to the second cell determines whether the previous handover is a premature handover or a handover to a wrong cell, the base station corresponding to the second cell sends a handover report to the first cell of the first RAT. The handover report is used to indicate whether the previous handover is a premature handover or a handover to a wrong cell. For example, the handover report sent by the base station corresponding to the second cell to the base station corresponding to the first cell of the first RAT carries information indicating whether the previous handover is a premature handover or a handover to a wrong cell. The base station corresponding to the second cell further sends the received connection failure information to the base station corresponding to the first cell. The connection failure information may alternatively be sent to the base station corresponding to the first cell in the form of a container. Optionally, when the second cell of the second RAT sends the connection failure information to the first cell, an RRC format corresponding to the specific RAT used by the connection failure information, or an RRC format of the specific RAT in which the connection failure information is encoded, or an RRC format of the specific RAT in which the UE performs encoding is additionally carried. The first cell of the first RAT may optimize mobility parameters after receiving this information. The second cell of the second RAT may send the connection failure information to the base station corresponding to the first cell over the core network (i.e., the connection failure information is first sent to the core network, and then the core network forwards the connection failure information to the base station corresponding to the first cell). The second cell of the second RAT may alternatively send the connection failure information to the base station corresponding to the first cell through an interface between base stations (e.g., an Xn interface). Optionally, when the second cell of the second RAT sends connection failure information to the first cell (e.g., the second cell sends connection failure information to the core network), an identifier reported by the UE of the serving cell to which the UE is unsuccessfully handed over is additionally carried. Optionally, the TAC of the serving cell may be further carried.For the description of the identifier and TAC of the serving cell to which the UE is handed over, please refer to the description in S602, and the details will not be described again here.

[0198] It may be understood that the embodiments, terminal devices and / or network devices of the present application may perform some or all of the steps in the embodiments of the present application. These steps or operations are merely examples. In the embodiments of the present application, other operations or variations of various operations may be further performed. In addition, these steps may be performed in an order different from the order presented in the embodiments of the present application, and not all of the operations in the embodiments of the present application are necessarily performed. The communication method in the embodiments of the present application has been described in detail above. In order to better implement the aforementioned solution in the embodiments of the present application, the embodiments of the present application further provide a corresponding apparatus or device.

[0199] 8 is a schematic structural diagram of an apparatus according to an embodiment of the present application. The apparatus may be a network device, or a chip or circuit that may be disposed in a network device. As shown in FIG. 8, the device 1 includes: a first transceiver unit 10 configured to receive connection failure information from a terminal device, the connection failure information being used to indicate that the terminal device detects a radio link failure (RLF) in a first cell or fails to be handed over to the first cell, and there is a radio connection between the terminal device and the second cell in a handover procedure from the second cell to the first cell, the second cell being a cell managed by a first network device; and a first determining unit 20 configured to determine a connection failure type of the terminal device. The first cell may be a target cell and the second cell may be a source cell.

[0200] In some possible implementations, the first determining unit 20 is specifically configured to determine that the connection failure type of the terminal device is premature handover when the first determining unit 20 determines that the terminal device holds a radio connection to the second cell after the terminal device detects an RLF in the first cell or fails to be handed over to the first cell, or to determine that the connection failure type of the terminal device is handover to an incorrect cell when the first determining unit 20 determines that the third cell is a cell accessed by the terminal device, and the third cell is different from the first cell and the second cell.

[0201] In some possible implementations, the first cell is a candidate cell that is within at least one candidate cell of the terminal device and satisfies a CHO trigger condition, and the third cell is different from any one of the second cell and the at least one candidate cell.

[0202] In some possible implementations, the connection failure information is used to indicate that the terminal device fails to be handed over to the first cell. The first transceiver unit 10 is further configured to send first indication information to the terminal device. The first indication information is used to indicate the terminal device to access the second cell when the terminal device fails to be handed over to the first cell.

[0203] The first determining unit 20 may be a processing unit.

[0204] During a specific implementation, for the implementation of each module or unit, please refer to the corresponding description of the first network device in the method embodiment shown in Figure 2 or Figure 6 accordingly to perform the methods and functions performed by the first network device in the above embodiments.

[0205] According to this embodiment of the present application, the network device implements mobility robustness optimization by determining premature handover and handover to an incorrect cell when RRC re-establishment is not performed in a mobility enhancement scenario or a CHO scenario and optimizing mobility parameters.

[0206] 9 is another schematic structural diagram of an apparatus according to an embodiment of the present application. The apparatus may be a network device, or a chip or circuit that may be disposed in the network device. As shown in FIG. 9, the apparatus 2 may include: a second transceiver unit 30 configured to receive connection failure information, the connection failure information being used to indicate that the terminal device detects an RLF in a first cell in a handover procedure from the first cell to the second cell, the first cell being a cell managed by the first network device; and a second determining unit 40 configured to determine a connection failure type of the terminal device.

[0207] In some possible implementations, the second determination unit 40 is specifically configured to determine that the connection failure type of the terminal device is too late handover when the second determination unit 40 determines that the time that the terminal device is camped on the first cell is greater than a second threshold and the terminal device successfully accesses the second cell.

[0208] In this application, the time that a terminal device is camped on a first cell is the time that the terminal device maintains an RRC connection to the first cell, or the time that the terminal device maintains a radio connection to the first cell, or the time that the terminal device has a connection to the first cell but has not received a handover command.

[0209] In some possible implementations, the second cell is a candidate cell that is within at least one candidate cell of the terminal device and satisfies a CHO trigger condition.

[0210] The second determining unit 40 may be a processing unit.

[0211] During a specific implementation, for the implementation of each module or unit, please refer to the corresponding description of the first network device in the method embodiment shown in Figure 3 or Figure 5 accordingly to perform the methods and functions performed by the first network device in the above embodiments.

[0212] According to this embodiment of the present application, the network device implements mobility robustness optimization by determining handover too late and optimizing mobility parameters when RRC re-establishment is not performed in a mobility enhancement scenario or a CHO scenario.

[0213] 10 is yet another schematic structural diagram of an apparatus according to an embodiment of the present application. The apparatus may be a network device, or a chip or circuit that may be disposed in a network device. As shown in FIG. 10, the apparatus 3 includes: a third transceiver unit 50 configured to receive connection failure information from a second network device, the connection failure information being used to indicate that the terminal device detects an RLF in a master cell group MCG managed by the first network device; and a third determining unit 60 configured to determine a connection failure type of the terminal device. may include.

[0214] In some possible implementations, the third determining unit 60 is specifically configured to determine that the connection failure type of the terminal device is too late handover when the third determining unit 60 determines that the fourth cell is the cell accessed by the terminal device, and the fourth cell is different from the primary cell in the MCG managed by the first network device.

[0215] In some possible implementations, the third determination unit 60 is specifically configured to determine that the connection failure type of the terminal device is premature handover when the third determination unit 60 determines that the fifth cell is a cell accessed by the terminal device, and the fifth cell is a cell accessed before the primary cell in the MCG managed by the first network device is handed over, or to determine that the connection failure type of the terminal device is handover to an incorrect cell when the third determination unit 60 determines that the sixth cell is a cell accessed by the terminal device, and the sixth cell is different from the primary cell in the MCG managed by the first network device and the fifth cell.

[0216] In some possible implementations, the third transceiver unit 50 is further configured to send second indication information to the source master network device, the second indication information being used to indicate that the connection failure type of the terminal device is premature handover or handover to an incorrect cell.

[0217] The third determining unit 60 may be a processing unit.

[0218] During a specific implementation, for the implementation of each module or unit, please refer to the corresponding description of the first network device in the method embodiment shown in FIG. 4 to perform the methods and functions performed by the first network device in the above embodiment accordingly.

[0219] According to this embodiment of the present application, the network device implements mobility robustness optimization by determining handover too late, handover too early and handover to a wrong cell when RLF occurs within an MCG in a dual connectivity scenario and optimizing mobility parameters.

[0220] 11 is a schematic structural diagram of a communication device according to an embodiment of the present application. As shown in FIG. 11, the communication device 1000 provided in this embodiment of the present application includes a processor 1001, a memory 1002, a transceiver 1003 and a bus system 1004. The communication device provided in this embodiment of the present application may be any one of a first network device, a second network device and a terminal device.

[0221] The processor 1001 , the memory 1002 and the transceiver 1003 are connected using a bus system 1004 .

[0222] The memory 1002 is configured to store a program. Specifically, the program may include a program code, and the program code includes computer operation instructions. The memory 1002 includes, but is not limited to, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read only memory (EPROM) or a compact disc read-only memory (CD-ROM). Only one memory is shown in FIG. 11. Of course, multiple memories can be arranged as needed. The memory 1002 may alternatively be a memory in the processor 1001. This is not limited in this specification.

[0223] The memory 1002 includes Operational instructions including various operational instructions for implementing various operations; and An operating system that includes various system programs to implement various basic services and handle hardware-based tasks or a subset or extension thereof.

[0224] The processor 1001 controls the operation of the communication device 1000. The processor 1001 may be one or more central processing units (CPUs). When the processor 1001 is one CPU, the CPU may be a single-core CPU or a multi-core CPU.

[0225] During particular applications, the components of the communication device 1000 are coupled together using a bus system 1004. In addition to a data bus, the bus system 1004 may include a power bus, a control bus, a status signal bus, etc. However, for clarity of illustration, the various buses in FIG. 11 are illustrated as the bus system 1004. For ease of illustration, FIG. 11 illustrates only one example of the bus system 1004.

[0226] Any one of the methods of the first network device disclosed in the embodiments of FIG. 2 to FIG. 6 or the above-mentioned embodiments provided in the embodiments of the present application, any one of the methods of the terminal device in the embodiments of FIG. 2 to FIG. 6 or the above-mentioned embodiments provided in the embodiments of the present application, or any one of the methods of the second network device in the embodiments of FIG. 3 to FIG. 5 provided in the embodiments of the present application or the above-mentioned embodiments may be applied to the processor 1001 or may be implemented by the processor 1001. The processor 1001 may be an integrated circuit chip and has a signal processing capability. In the implementation process, each stage in the above-mentioned method may be completed by using an integrated logic circuit of hardware in the processor 1001 or an instruction in the form of software. The above-mentioned processor 1001 may be a general-purpose processor, a digital signal processing (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or another programmable logic device, a discrete gate or transistor logic device, or a discrete hardware component. The processor may implement or execute the methods, steps and logic block diagrams disclosed in the embodiments of the present application. The general-purpose processor may be a microprocessor, and the processor may be any conventional processor, etc. The steps of the methods disclosed with reference to the embodiments of the present application may be directly executed and completed by a hardware decode processor, or may be executed and completed by using a combination of hardware modules and software modules in the decode processor. The software modules may be located in a storage medium mature in the art, such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory, an electrically erasable programmable memory or a register.The storage medium is located in memory 1002, and the processor 1001 reads information in the memory 1002 and, in combination with the hardware of the processor 1001, performs steps of a method for a first network device described in any one of Figures 2 to 6, or, in combination with the hardware of the processor 1001, performs steps of a method for a terminal device described in any one of Figures 2 to 6, or, in combination with the hardware of the processor 1001, performs steps of a method for a second network device described in any one of Figures 3 to 5.

[0227] An embodiment of the present application further provides a computer program product, the computer program product including a computer program code, which, when executed on a computer, enables the computer to perform steps of the first network device method described in Figure 2, Figure 3, Figure 4, Figure 5 or Figure 6, or, when executed on a computer, enables the computer to perform steps of the terminal device method described in Figure 2, Figure 3, Figure 4, Figure 5 or Figure 6.

[0228] An embodiment of the present application further provides an apparatus. The apparatus may be a chip. The chip includes a processor. The processor is configured to execute the mobility optimization method according to any one of the possible implementations in FIG. 2 to FIG. 6 by reading and executing a computer program stored in a memory. Optionally, the chip further includes a memory, and the memory is connected to the processor by using a circuit or a wire. Furthermore, optionally, the chip further includes a communication interface, and the processor is connected to the communication interface. The communication interface is configured to receive data and / or information that needs to be processed. The processor obtains the data and / or information from the communication interface, processes the data and / or information, and outputs the processing result through the communication interface. The communication interface may be an input / output interface.

[0229] Optionally, the processor and memory may be physically separate units, or the memory may be integrated with the processor.

[0230] Another embodiment of the present application further provides a communication system. The communication system includes a first network device, and optionally further includes a terminal device. Alternatively, the communication system includes a first network device and a second network device, and optionally further includes a terminal device. For example, the first network device may be the first network device in the mobility optimization method provided in FIG. 2 or FIG. 6, and the terminal device may be the terminal device in the mobility optimization method provided in FIG. 2 or FIG. 6. Alternatively, the first network device may be the first network device in the mobility optimization method provided in FIG. 3 to FIG. 5, the second network device may be the second network device in the mobility optimization method provided in FIG. 3 to FIG. 5, and the terminal device may be the terminal device in the mobility optimization method provided in FIG. 3 to FIG. 5.

[0231] Those skilled in the art can understand that all or some of the steps of the method in the embodiment can be implemented by a computer program that instructs relevant hardware. The program can be stored in a computer-readable storage medium. When the program is executed, the steps in the method embodiment can be included. The storage medium includes any medium that can store program code, such as ROM or random access memory RAM, magnetic disk or compact disk.

[0232] The above description is merely a specific implementation of the present application, and is not intended to limit the scope of protection of the present application. Any modifications or replacements that a person skilled in the art can easily conceive within the technical scope disclosed in the present application shall be included in the scope of protection of the present application. Therefore, the scope of protection of the present application shall be subject to the scope of protection of the claims. [Other possible items] [Item 1] A mobility optimization method, comprising: receiving connection failure information from a terminal device by a first network device, the connection failure information being used to indicate that the terminal device has detected a radio link failure (RLF) in a first cell or has failed to be handed over to the first cell, and there is a radio connection between the terminal device and the second cell in a handover procedure from a second cell to the first cell, the second cell being a cell managed by the first network device; the first network device determining a connection failure type of the terminal device; A method comprising: [Item 2] the first cell is a target cell and the second cell is a source cell; The step of the first network device determining a connection failure type of the terminal device includes: if the first network device determines that the terminal device maintains the radio connection to the second cell after the terminal device has detected the RLF in the first cell or has failed to be handed over to the first cell, the first network device determines that the connection failure type of the terminal device is premature handover; or determining, by the first network device, if the first network device determines that a third cell is a cell accessed by the terminal device, that the connection failure type of the terminal device is a handover to an incorrect cell, the third cell being different from the first cell and the second cell. having one or both of The method according to item 1. [Item 3] The method according to item 2, wherein the first cell is a candidate cell that is within at least one candidate cell of the terminal device and satisfies a conditional inter-cell handover CHO trigger condition, and the third cell is different from the second cell and any one of the at least one candidate cell. [Item 4] Prior to the step of the first network device receiving connection failure information from the terminal device, a step of the first network device transmitting first indication information to the terminal device, the first indication information being used to indicate the terminal device to access the second cell if the terminal device fails to be handed over to the first cell; The method of claim 3, further comprising: [Item 5] A mobility optimization method, comprising: receiving, by a first network device, connection failure information, the connection failure information being used to indicate that a terminal device has detected an RLF in a first cell in a handover procedure from a first cell to a second cell, the first cell being a cell managed by the first network device; the first network device determining a connection failure type of the terminal device; A method comprising: [Item 6] The step of the first network device determining a connection failure type of the terminal device includes: determining, by the first network device, if the time that the terminal device has camped on the first cell is greater than a second threshold and the terminal device has successfully accessed the second cell, that the connection failure type of the terminal device is a too late handover. having The method according to item 5. [Item 7] 7. The method of claim 6, wherein the second cell is a candidate cell that is within at least one candidate cell of the terminal device and satisfies a CHO trigger condition. [Item 8] receiving, by a first network device, connection failure information from a second network device, the connection failure information being used to indicate that a terminal device has detected an RLF in a master cell group (MCG) managed by the first network device; the first network device determining a connection failure type of the terminal device; A mobility optimization method comprising: [Item 9] receiving, by a first network device, connection failure information, the connection failure information being used to indicate that a terminal device has detected an RLF in a first cell or has failed to be handed over from the first cell to a second cell; the first network device determining a connection failure type of the terminal device; A mobility optimization method comprising: [Item 10] An apparatus, the apparatus being a network device or a chip or circuit arranged within the network device, the apparatus comprising a unit or module configured to perform the method according to any one of items 1 to 4. [Item 11] An apparatus, the apparatus being a network device or a chip or circuit arranged within the network device, comprising a unit or module configured to perform the method according to any one of items 5 to 7. [Item 12] An apparatus, the apparatus being a network device or a chip or circuit disposed within the network device, the apparatus comprising a unit or module configured to perform the method according to item 8. [Item 13] An apparatus, the apparatus being a network device or a chip or circuit disposed within the network device, the apparatus comprising a unit or module configured to perform the method according to item 9. [Item 14] An apparatus, the apparatus being a network device or a chip or circuit located within the network device, comprising a processor, a transceiver and a memory, the memory configured to store a computer program, the transceiver configured to receive and transmit information, the computer program including program instructions, the processor executing the program instructions enabling the apparatus to perform the method of any one of items 1 to 4. [Item 15] An apparatus, the apparatus being a network device or a chip or circuit located within the network device, comprising a processor, a transceiver and a memory, the memory configured to store a computer program, the transceiver configured to receive and transmit information, the computer program including program instructions, the processor executing the program instructions enabling the apparatus to perform the method of any one of items 5 to 7. [Item 16] An apparatus, the apparatus being a network device or a chip or circuit located within the network device, comprising a processor, a transceiver and a memory, the memory configured to store a computer program, the transceiver configured to receive and transmit information, the computer program including program instructions, the processor executing the program instructions enabling the apparatus to perform the method described in item 8. [Item 17] 10. An apparatus, the apparatus being a network device or a chip or circuit located within the network device, comprising a processor, a transceiver and a memory, the memory configured to store a computer program, the transceiver configured to receive and transmit information, the computer program including program instructions, the processor executing the program instructions enabling the apparatus to perform the method of claim 9. [Item 18] A communication system comprising a first network device and a terminal device, The first network device is a network device for performing the method according to any one of items 1 to 7, The terminal device is a terminal device for executing the method according to any one of items 1 to 7; Communication systems. [Item 19] 5. A readable storage medium having stored thereon program instructions which, when executed, perform the method of any one of items 1 to 4. [Item 20] 8. A readable storage medium having stored thereon program instructions which, when executed, perform the method according to any one of items 5 to 7. [Item 21] 9. A readable storage medium having program instructions stored thereon that, when executed, perform the method of claim 8. [Item 22] 10. A readable storage medium having stored thereon program instructions that, when executed, perform the method of claim 9. [Other possible items] [Item 1] 1. A communication method comprising: a terminal device determining connection failure information; transmitting the connection failure information and an identifier of a first cell to a first network device by using a radio resource control (RRC) message, the identifier of the first cell comprising an identifier of a cell from which a reconfiguration or handover command message received by the terminal device comes or an identifier of a cell where a connection failure occurs; the connection failure information is in the form of a container in the RRC message, and the identifier of the first cell is outside the container. method. [Item 2] 2. The method of claim 1, further comprising: a handover failure occurs in a procedure in which the terminal device attempts to be handed over from the first cell of a source network device to a second cell of a target network device, the first cell being the cell from which the reconfiguration message or the handover command message received by the terminal device comes, and the first cell and the second cell use different radio access technologies. [Item 3] accessing a third cell of the first network device by the terminal device before transmitting the RRC message, the second cell and the third cell using the same radio access technology. The method of claim 2, further comprising: [Item 4] 2. The method of claim 1, further comprising: a radio link failure occurs on the terminal device in the first cell of a source network device, the first cell being the cell in which the connection failure occurs. [Item 5] accessing, by the terminal device, a third cell of the first network device before transmitting the RRC message, the first cell and the third cell using different radio access technologies. 5. The method of claim 4, further comprising: [Item 6] 6. The method according to any one of items 1 to 5, wherein the radio access technology used by a cell of the first network device accessed by the terminal device is New Radio NR, and the radio access technology used by the first cell is Evolved Universal Terrestrial Radio Access (E-UTRA). [Item 7] 1. A communication method comprising: receiving, by a first network device, a radio resource control (RRC) message from a terminal device, the RRC message including connection failure information and an identifier of a first cell, the identifier of the first cell including an identifier of a cell from which a reconfiguration message or a handover command message received by the terminal device comes or an identifier of a cell where a connection failure occurs; determining the identifier of the first cell based on the RRC message; the connection failure information is in the form of a container in the RRC message, and the identifier of the first cell is outside the container. method. [Item 8] a step of the first network device transmitting the connection failure information and information indicating a radio access technology in an RRC format used by the connection failure information to the second network device through an interface between the first network device and a second network device, the second network device managing the first cell; 8. The method of claim 7, further comprising: [Item 9] a step of the first network device transmitting the connection failure information and information indicating a radio access technology in an RRC format used by the connection failure information to a second network device by using a core network device, the second network device managing the first cell; 8. The method of claim 7, further comprising: [Item 10] 10. The method according to any one of claims 7 to 9, wherein the cell managed by the first network device is a cell of a first radio access technology, and the first cell uses a second radio access technology. [Item 11] 1. A communication method comprising: A second network device receives, from the first network device, connection failure information and information indicating a radio access technology in an RRC format used by the connection failure information, through an interface between the second network device and the first network device or by using a core network device; the second network device determining, based on the information indicating the radio access technology of the RRC format used by the connection failure information, the radio access technology of the RRC format used by the connection failure information; A method comprising: [Item 12] Item 12. The method of item 11, wherein the first network device and the second network device use different radio access technologies. [Item 13] An apparatus, the apparatus being a terminal device or a chip or circuit arranged in the terminal device, the apparatus comprising a unit or module configured to perform the method according to any one of items 1 to 6. [Item 14] 7. An apparatus, the apparatus being a terminal device or a chip or circuit arranged in the terminal device, comprising a processor and a memory, the memory being configured to store a computer program, the computer program comprising program instructions, the apparatus being enabled to perform the method according to any one of claims 1 to 6 when the processor executes the program instructions. [Item 15] An apparatus, the apparatus being a network device or a chip or circuit arranged in the network device, the apparatus comprising a unit or module configured to perform the method according to any one of items 7 to 10. [Item 16] 13. An apparatus, the apparatus being a network device or a chip or circuit located within the network device, comprising a processor and a memory, the memory configured to store a computer program, the computer program including program instructions, the processor executing the program instructions enabling the apparatus to perform the method according to item 11 or 12. [Item 17] An apparatus, the apparatus being a network device or a chip or circuit arranged in the network device, the apparatus comprising a unit or module configured to perform the method according to any one of items 7 to 10. [Item 18] 13. An apparatus, the apparatus being a network device or a chip or circuit located within the network device, comprising a processor and a memory, the memory configured to store a computer program, the computer program including program instructions, the processor executing the program instructions enabling the apparatus to perform the method according to item 11 or 12. [Item 19] A communication system comprising the device according to item 15 or 16 and the device according to item 17 or 18. [Item 20] 20. The system of claim 19, further comprising the device of claim 13 or 14. [Item 21] A readable storage medium or a program product, the readable storage medium or the program product storing program instructions, which, when executed, perform the method according to any one of items 1 to 6, any one of items 7 to 10, or item 11 or 12. [Item 22] 1. A communication method comprising: receiving, by a third network device, connection failure information from a terminal device, the connection failure information indicating that the terminal device detects a radio link failure (RLF) in a second cell of a second network device after the terminal device has been successfully handed over from a first cell of a first network device to a second cell; the third network device transmitting the connection failure information and information indicating a radio access technology in a radio resource control (RRC) format used by the connection failure information to the second network device; A method comprising: [Item 23] 23. The method of claim 22, wherein the connection failure information received from the terminal device is in the form of a container of an RRC message. [Item 24] the third network device transmitting the connection failure information and the information indicating the radio access technology in the RRC format used by the connection failure information to the second network device through an interface between the third network device and the second network device. 24. The method of claim 22 or 23, further comprising: [Item 25] the third network device transmitting the connection failure information and the information indicating the radio access technology in the RRC format used by the connection failure information to the second network device by using a core network device. 24. The method of claim 22 or 23, further comprising: [Item 26] 26. The method according to any one of items 22 to 25, wherein the first cell of the first network device uses a first radio access technology, and the second cell of the second network device and a cell of the third network device use a second radio access technology. [Item 27] 1. A communication method comprising: receiving, by a second network device, connection failure information and information indicating a radio access technology in an RRC format used by the connection failure information from the third network device through an interface between the second network device and a third network device or by using a core network device, the connection failure information being received by the third network device from a terminal device and indicating that the terminal device has detected a radio link failure (RLF) in the second cell of the second network device after the terminal device has been successfully handed over from a first cell of a first network device to a second cell; the second network device determining, based on the information indicating the radio access technology of the RRC format used by the connection failure information, the radio access technology of the RRC format used by the connection failure information; A method comprising: [Item 28] 28. The method of claim 27, wherein the first cell of the first network device uses a first radio access technology, and the second cell of the second network device and a cell of the third network device use a second radio access technology. [Item 29] 27. An apparatus, the apparatus being a network device or a chip or circuit arranged within the network device, the apparatus comprising a unit or module configured to perform the method according to any one of items 22 to 26. [Item 30] 27. An apparatus, the apparatus being a network device or a chip or circuit located within the network device, comprising a processor and a memory, the memory configured to store a computer program, the computer program including program instructions, the apparatus being capable of performing the method of any one of items 22 to 26 when the processor executes the program instructions. [Item 31] 29. An apparatus, the apparatus being a network device or a chip or circuit arranged in the network device, the apparatus comprising a unit or module configured to perform the method according to item 27 or 28. [Item 32] 29. An apparatus, the apparatus being a network device or a chip or circuit located within the network device, comprising a processor and a memory, the memory configured to store a computer program, the computer program including program instructions, the processor executing the program instructions enabling the apparatus to perform the method according to item 27 or 28. [Item 33] A communication system comprising the device according to item 29 or 30 and the device according to item 31 or 32. [Item 34] A readable storage medium or a program product, the readable storage medium or the program product storing program instructions, which, when executed, perform the method of any one of items 22 to 26, or item 27 or 28. [Item 35] A mobility optimization method, comprising: receiving connection failure information from a terminal device by a first network device, the connection failure information being used to indicate that the terminal device has detected a radio link failure (RLF) in a first cell or has failed to be handed over to the first cell, and there is a radio connection between the terminal device and the second cell in a handover procedure from a second cell to the first cell, the second cell being a cell managed by the first network device; the first network device determining a connection failure type of the terminal device; A method comprising: [Item 36] the first cell is a target cell and the second cell is a source cell; The step of the first network device determining a connection failure type of the terminal device includes: if the first network device determines that the terminal device maintains the radio connection to the second cell after the terminal device has detected the RLF in the first cell or has failed to be handed over to the first cell, the first network device determines that the connection failure type of the terminal device is premature handover; or determining, by the first network device, if the first network device determines that a third cell is a cell accessed by the terminal device, that the connection failure type of the terminal device is a handover to an incorrect cell, the third cell being different from the first cell and the second cell. having one or both of The method according to item 35. [Item 37] Item 37. The method according to item 36, wherein the first cell is a candidate cell that is within at least one candidate cell of the terminal device and satisfies a conditional inter-cell handover (CHO) trigger condition, and the third cell is different from the second cell and any one of the at least one candidate cell. [Item 38] Prior to the step of the first network device receiving connection failure information from the terminal device, a step of the first network device transmitting first indication information to the terminal device, the first indication information being used to indicate the terminal device to access the second cell if the terminal device fails to be handed over to the first cell; Item 38. The method of item 37, further comprising: [Item 39] A mobility optimization method, comprising: receiving, by a first network device, connection failure information, the connection failure information being used to indicate that a terminal device has detected an RLF in a first cell in a handover procedure from a first cell to a second cell, the first cell being a cell managed by the first network device; the first network device determining a connection failure type of the terminal device; A method comprising: [Item 40] The step of the first network device determining a connection failure type of the terminal device includes: determining, by the first network device, if the time that the terminal device has camped on the first cell is greater than a second threshold and the terminal device has successfully accessed the second cell, that the connection failure type of the terminal device is a too late handover. having Item 39. The method according to item 39. [Item 41] Item 41. The method of item 40, wherein the second cell is a candidate cell that is within at least one candidate cell of the terminal device and satisfies a CHO trigger condition. [Item 42] receiving, by a first network device, connection failure information from a second network device, the connection failure information being used to indicate that a terminal device has detected an RLF in a master cell group (MCG) managed by the first network device; the first network device determining a connection failure type of the terminal device; A mobility optimization method comprising: [Item 43] receiving, by a first network device, connection failure information, the connection failure information being used to indicate that a terminal device has detected an RLF in a first cell or has failed to be handed over from the first cell to a second cell; the first network device determining a connection failure type of the terminal device; A mobility optimization method comprising: [Item 44] An apparatus, the apparatus being a network device or a chip or circuit disposed within the network device, the apparatus comprising a unit or module configured to perform the method according to any one of items 35 to 38, any one of items 39 to 41, item 42, or item 43. [Item 45] An apparatus, the apparatus being a network device or a chip or circuit located within the network device, comprising a processor, a transceiver and a memory, the memory configured to store a computer program, the transceiver configured to receive and transmit information, the computer program including program instructions, which when executed by the processor enables the apparatus to perform the method of any one of items 35 to 38, any one of items 39 to 41, item 42, or item 43. [Item 46] A readable storage medium or a program product having program instructions stored thereon, the program instructions, when executed, performing the method of any one of items 35 to 38, any one of items 39 to 41, item 42, or item 43.

Claims

1. A communication method implemented by a terminal device or a chip for said terminal device, comprising: recording connection failure information; accessing a third cell of the first network device; transmitting the connection failure information and an identifier of a first cell to the first network device by using a Radio Resource Control (RRC) message, the first cell being a cell from which a reconfiguration message or a handover command message is received by the terminal device, and a handover failure occurs in a procedure in which the terminal device attempts to be handed over from the first cell of a source network device to a second cell of a target network device; Equipped with the first cell uses a first radio access technology, the second cell and the third cell use a second radio access technology different from the first radio access technology, the connection failure information is in the form of a container in the RRC message, and the identifier of the first cell is outside the container; Type information of the first cell, or the type information of the first cell and a Tracking Area Code (TAC) of the first cell are carried in the RRC message and are outside the container; The method, wherein the type information indicates that the first cell is a Long Term Evolution (LTE) cell, an eLTE cell, or a New Radio (NR) cell.

2. 2. The method of claim 1, wherein the second radio access technology is a new radio access technology (NR) and the first radio access technology is an evolved universal terrestrial radio access technology (E-UTRAN).

3. The method of claim 1 or 2, wherein the identifier of the first cell comprises a Cell Global Identifier (CGI).

4. A communication method implemented by a terminal device or a chip for said terminal device, comprising: recording connection failure information; accessing a third cell of the first network device; transmitting the connection failure information and an identifier of a first cell to the first network device by using a Radio Resource Control (RRC) message, the first cell being a cell in which a radio link failure occurs on the terminal device; the first cell uses a first radio access technology and the third cell uses a second radio access technology different from the first radio access technology, the connection failure information is in the form of a container in the RRC message, and the identifier of the first cell is outside the container; Type information of the first cell, or the type information of the first cell and a Tracking Area Code (TAC) of the first cell are carried in the RRC message and are outside the container; The method, wherein the type information indicates that the first cell is a Long Term Evolution (LTE) cell, an eLTE cell, or a New Radio (NR) cell.

5. 5. The method of claim 4, wherein the radio access technology used by the third cell is a new radio access technology (NR) and the radio access technology used by the first cell is an evolved universal terrestrial radio access technology (E-UTRAN).

6. 1. A communication method performed by a first network device or a chip for said first network device, comprising: receiving a Radio Resource Control (RRC) message from a terminal device, the RRC message including connection failure information and an identifier of a first cell, the first cell being a cell from which a reconfiguration message or a handover command message received by the terminal device originates, and a handover failure occurs in a procedure in which the terminal device attempts to be handed over from the first cell of a source network device to a second cell of a target network device; determining the identifier of the first cell based on the RRC message; Equipped with The first cell uses a first radio access technology, and the second cell and a third cell managed by the first network device use a second radio access technology different from the first radio access technology, the connection failure information is in the form of a container in the RRC message, and the identifier of the first cell is outside the container; Type information of the first cell, or the type information of the first cell and a Tracking Area Code (TAC) of the first cell are carried in the RRC message and are outside the container; The method, wherein the type information indicates that the first cell is a Long Term Evolution (LTE) cell, an eLTE cell, or a New Radio (NR) cell.

7. 1. A communication method performed by a first network device or a chip for said first network device, comprising: receiving a Radio Resource Control (RRC) message from a terminal device, the RRC message including connection failure information and an identifier of a first cell, the first cell being a cell in which a radio link failure occurs on the terminal device; determining the identifier of the first cell based on the RRC message; Equipped with the first cell uses a first radio access technology, and a third cell managed by the first network device uses a second radio access technology different from the first radio access technology, the connection failure information is in the form of a container in the RRC message, and the identifier of the first cell is outside the container; Type information of the first cell, or the type information of the first cell and a Tracking Area Code (TAC) of the first cell are carried in the RRC message and are outside the container; The method, wherein the type information indicates that the first cell is a Long Term Evolution (LTE) cell, an eLTE cell, or a New Radio (NR) cell.

8. a step of the first network device transmitting the connection failure information and information indicating a radio access technology of an RRC format used by the connection failure information to the second network device through an interface between the first network device and a second network device, the second network device managing the first cell; The method of claim 6 or 7, further comprising:

9. a step of the first network device transmitting the connection failure information and information indicating a radio access technology of an RRC format used by the connection failure information to a second network device through a core network device, the second network device managing the first cell; The method of claim 6 or 7, further comprising:

10. The method of claim 8 or 9, wherein the first network device transmits the connection failure information to the second network device based on the identifier of the first cell.

11. 10. The method according to claim 6, wherein the first radio access technology is an Evolved Universal Terrestrial Radio Access Technology (E-UTRAN) and the second radio access technology is a New Radio Access Technology (NR).

12. 1. A communication method performed by a second network device or a chip for the second network device, comprising: receiving connection failure information and information indicating a radio access technology in an RRC format used by the connection failure information from the first network device through an interface between the second network device and the first network device or through a core network device, the connection failure information being transmitted in the form of a container in an RRC message, an identifier of a first cell of the second network device being included outside the container, and type information of the first cell, or the type information of the first cell and a Tracking Area Code (TAC) of the first cell being carried in the RRC message; a first cell is outside the container, the type information indicating that the first cell is a Long Term Evolution (LTE) cell, an eLTE cell, or a New Radio (NR) cell, the first cell of the second network device is a cell that has sent a reconfiguration message or a handover command message to a terminal device, and a handover failure has occurred in a procedure in which the terminal device attempts to be handed over from the first cell of the second network device to a second cell of a target network device, or the first cell of the second network device is a cell in which a connection failure has occurred; determining the radio access technology of the RRC format used by the connection failure information based on the information indicating the radio access technology of the RRC format used by the connection failure information; Equipped with A method according to claim 1, wherein the first cell of the second network device uses a first radio access technology, and the second cell of the target network device and a third cell managed by the first network device use a second radio access technology different from the first radio access technology.

13. 6. An apparatus, the apparatus being a terminal device or a chip or circuit arranged in the terminal device, the apparatus comprising a unit or module configured to perform the method according to any one of claims 1 to 5.

14. 6. An apparatus, the apparatus being a terminal device or a chip or circuit located in the terminal device, comprising a processor and a memory, the memory configured to store a computer program, the computer program comprising program instructions, the processor executing the program instructions enabling the apparatus to perform the method of any one of claims 1 to 5.

15. An apparatus, the apparatus being a network device or a chip or circuit located within the network device, the apparatus comprising a unit or module configured to perform the method of any one of claims 6 to 11.

16. 12. An apparatus, the apparatus being a network device or a chip or circuit located within the network device, comprising a processor and a memory, the memory configured to store a computer program, the computer program including program instructions, the processor executing the program instructions enabling the apparatus to perform a method according to any one of claims 6 to 11.

17. An apparatus, the apparatus being a network device or a chip or circuit located within the network device, the apparatus comprising a unit or module configured to perform the method according to claim 12.

18. 13. An apparatus, the apparatus being a network device or a chip or circuit located within the network device, comprising a processor and a memory, the memory configured to store a computer program, the computer program including program instructions, the processor executing the program instructions enabling the apparatus to perform the method of claim 12.

19. A communication system comprising an apparatus according to claim 15 or 16 and an apparatus according to claim 17 or 18.

20. 20. The system of claim 19, further comprising an apparatus according to claim 13 or 14.

21. A computer program which, when executed, performs the method of any one of claims 1 to 5.

22. A computer program which, when executed, performs the method of any one of claims 6 to 11.

23. A computer program which, when executed, performs the method of claim 12.

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