Communication method and communications apparatus
地域：
Shenzhen
摘要
This application provides a communication method and a communications apparatus. The method includes: receiving, by a terminal device, conditional handover configuration information from a first network device, where the first network device is a network device to which a serving cell belongs, and the serving cell is a cell that currently accessed by the terminal belongs; and determining, by the terminal device, a first target cell based on the conditional handover configuration information.
說明書
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This application is a continuation of International Application No. PCT/CN2019/127836, filed on Dec. 24, 2019, which claims priority to Chinese Patent Application No. 201811603870.2, filed on Dec. 26, 2018. The disclosures of the aforementioned applications are hereby incorporated by reference in their entireties.
This application relates to the communications field, and more specifically, to a communication method and a communications apparatus.
In a mobile communications system, mobility management of a terminal device in connected mode is controlled by a network device. To be specific, the network device sends a handover message to indicate a target cell to which the terminal device is to be handed over and a handover method.
Whether the handover message can be successfully sent strongly depends on serving link quality of a source cell. A serving link with poor quality causes a failure in sending the handover message. Consequently, the terminal device cannot be handed over, and data transmission is affected. In a long term evolution (LTE) or a 5th generation (5G) mobile communications technology (especially in a high-frequency scenario), fast channel quality attenuation, fast movement of a terminal device, or blocking by an object all affect serving link quality. These factors may cause a failure in sending a handover message, resulting in a low handover success rate.
Therefore, how to improve a handover success rate becomes an urgent problem to be resolved.
權利要求
What is claimed is:1. A method, comprising:receiving conditional handover configuration information from a first network device, wherein the first network device is a network device to which a serving cell belongs, and the serving cell is a cell that is currently accessed by a terminal device; determining a first target cell based on the conditional handover configuration information, wherein determining the first target cell comprises:receiving a handover message from the first network device in a process of determining the first target cell, wherein the handover message comprises an identifier of a second target cell and a dedicated random access resource required for accessing the second target cell, and the dedicated random access resource comprises a preamble index and a time-frequency resource; stopping determining the first target cell based on the conditional handover configuration information, and performing contention-free random access to the second target cell based on the dedicated random access resource; and determining, based on the conditional handover configuration information when the contention-free random access to the second target cell fails, the first target cell. 2. The method according to claim 1 , wherein the conditional handover configuration information configures a first measurement object and a handover condition threshold, wherein a measurement result of the first measurement object and the handover condition threshold are used to determine whether a trigger condition of a conditional handover is satisfied; andwherein determining the first target cell based on the conditional handover configuration information comprises:determining a candidate target cell that corresponds to the first measurement object and that satisfies the trigger condition as the first target cell based on the measurement result of the first measurement object and the handover condition threshold. 3. The method according to claim 2 , wherein the conditional handover configuration information comprises the first measurement object and the handover condition threshold. 4. The method according to claim 3 , wherein the conditional handover configuration information further comprises at least one of the following information:a measurement identifier associated with the first measurement object and the handover condition threshold, an event corresponding to the handover condition threshold, a hysteresis value, or a time to trigger (TTT). 5. The method according to claim 2 , wherein the conditional handover configuration information comprises at least one of the following information:a cell identifier of the candidate target cell, frequency information of the candidate target cell, a C-RNTI allocated by the candidate target cell to the terminal device, an identifier of a first beam that belongs to the candidate target cell, or a first random access channel (RACH) resource. 6. The method according to claim 2 , wherein:the handover condition threshold comprises a first signal quality threshold, wherein when a difference between signal quality of the candidate target cell and signal quality of the serving cell is greater than or equal to the first signal quality threshold, the candidate target cell satisfies the trigger condition; or the handover condition threshold comprises a second signal quality threshold and a third signal quality threshold, wherein when signal quality of the candidate target cell is greater than or equal to the third signal quality threshold, and signal quality of the serving cell is less than the second signal quality threshold, the candidate target cell satisfies the trigger condition, wherein the third signal quality threshold is greater than or equal to the second signal quality threshold. 7. The method according to claim 2 , wherein the handover condition threshold corresponds to a quality level, and the quality level indicates a quality value range of the serving cell. 8. The method according to claim 1 , wherein after a handover is completed, the method further comprises:releasing the conditional handover configuration information. 9. The method according to claim 8 , wherein the handover is completed when the terminal device is successfully handed over to the first target cell. 10. A system, comprising:a terminal device; and a first target network device; wherein the terminal device is configured to:receive conditional handover configuration information from a source network device; and determine the first target network device based on the conditional handover configuration information, wherein determining the first target network device comprises:receiving a handover message from the source network device in a process of determining the first target network device, wherein the handover message comprises an identifier of a second target network device and a dedicated random access resource required for accessing the second target network device, and the dedicated random access resource comprises a preamble index and a time-frequency resource; stopping determining the first target network device based on the conditional handover configuration information, and performing contention-free random access to the second target network device based on the dedicated random access resource; and determining, based on the conditional handover configuration information when the contention-free random access to the second target network device fails, the first target network device. 11. The system according to claim 10 , wherein the first target network device is configured to:send a message B to the source network device to indicate to the source network device to release conditional handover configuration information. 12. The system according to claim 10 , wherein the first target network device is configured to:send a message B to indicate to the source network device to indicate to other one or more candidate network devices of the terminal device to release context information of the terminal device and a reserved resource to the terminal device. 13. The system according to claim 10 , wherein the first target network device is configured to receive a message A from the terminal device for completing a handover procedure to the first target network device, and the message A is a radio resource control reconfiguration complete message. 14. The system according to claim 10 , wherein the first target network device is configured to:receive, from the terminal device, a message A for completing a handover procedure to the first target network device; and send a message B to indicate to the source network device to initiate a procedure for releasing resources for conditional handover of the terminal device. 15. An apparatus, comprising:at least one processor; and a non-transitory memory coupled with the processor and storing instructions that, when executed by the processor, cause the apparatus to:receive conditional handover configuration information from a first network device, wherein the first network device is a network device to which a serving cell belongs, and the serving cell is a cell that is currently accessed by a terminal device; determine a first target cell based on the conditional handover configuration information, wherein determining the first target cell comprises:receiving a handover message from the first network device in a process of determining the first target cell, wherein the handover message comprises an identifier of a second target cell and a dedicated random access resource required for accessing the second target cell, and the dedicated random access resource comprises a preamble index and a time-frequency resource; stopping the determining the first target cell based on the conditional handover configuration information, and perform contention-free random access to the second target cell based on the dedicated random access resource; and determining, based on the conditional handover configuration information when the contention-free random access to the second target cell fails, the first target cell. 16. The apparatus according to claim 15 , wherein the instructions, when executed by the processor, further cause the apparatus to:release the conditional handover configuration information when a handover is completed. 17. The apparatus according to claim 16 , wherein the handover is completed when the terminal device is successfully handed over to the first target cell. 18. The apparatus according to claim 15 , wherein the conditional handover configuration information is used to configure a first measurement object and a handover condition threshold, wherein a measurement result of the first measurement object and the handover condition threshold are used to determine whether a trigger condition of a conditional handover is satisfied; andwherein the instructions, when executed by the processor, further cause the apparatus to:determine a candidate target cell that corresponds to the first measurement object and that satisfies the trigger condition as the first target cell based on the measurement result of the first measurement object and the handover condition threshold. 19. The apparatus according to claim 18 , wherein the conditional handover configuration information comprises the first measurement object and the handover condition threshold.
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