EP-3893548-B1 - COMMUNICATION METHOD AND COMMUNICATION APPARATUS

EP3893548B1EP 3893548 B1EP3893548 B1EP 3893548B1EP-3893548-B1

Inventors

YAN, LE
ZHANG, HONGPING
ZENG, QINGHAI
GENG, Tingting
YUAN, Shitong

Dates

Publication Date: 20260506
Application Date: 20191224

Claims (10)

A communication method performed by a terminal device or a chip in a terminal device, the terminal device accessing a serving cell belonging to a first network device, comprising: sending (820) a measurement report to the first network device; receiving (840) conditional handover configuration information from the first network device, wherein the conditional handover configuration information comprises a handover trigger condition to a first target cell; searching for the first target cell that satisfies the handover trigger condition based on the conditional handover configuration information receiving (850) a handover message from the first network device in a process of searching for 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; and stopping (860) the searching for the first target cell that satisfies the handover trigger condition based on the conditional handover configuration information, and performing (860) contention-free random access to the second target cell based on the dedicated random access resource; and continuing to search, based on the conditional handover configuration information when the contention-free random access to the second target cell fails, for the first target cell that satisfies the handover trigger condition.
The method according to claim 1, wherein after a handover is completed, the method further comprises: releasing the conditional handover configuration information.
The method according to claim 2, wherein that the handover is completed comprises: the terminal device is successfully handed over to the first target cell.
The method according to claim 2, wherein before the first target cell is determined, wherein the handover message comprises the identifier of the second target cell; wherein the handover is completed comprises: the terminal device is successfully handed over to the second target cell.
The method according to any one of claims 2-4, 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; and the determining a 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.
The method according to claim 5, wherein the conditional handover configuration information comprises the first measurement object and the handover condition threshold.
The method according to claim 5 or 6, wherein the handover condition threshold corresponds to a quality level, and the quality level is used to indicate a quality value range of the serving cell.
A terminal device or a chip in a terminal device, configured to implement the method according to any one of claims 1 to 7.
A computer-readable storage medium, wherein the computer-readable storage medium stores an instruction, and when the instruction is run on terminal device or a chip in a terminal device, causing the terminal device to performed the method according to any one of claims 1 to 7.
A communications system, comprising: a source network device, a terminal device and a target network device, wherein the target network device is configured to: receive (870), from the terminal device, a RRC reconfiguration complete message for completing a handover procedure to the target network device, and send (880) a Release notification message to indicate the source network device to initiate a procedure for releasing resources for conditional handover, characterized in that the terminal device is further configured to implement the method according to any one of claims 1-7.

Description

TECHNICAL FIELD This application relates to the communications field, and more specifically, to a communication method and a communications apparatus. BACKGROUND 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 (long term evolution, LTE) or a 5th generation (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. MEDIATEK INC: "Conditional Handover Procedures", 3GPP DRAFT; R2-1816959 discusses the RAN2 details of conditional handover (CHO) procedures. INTEL CORPORATION: "Discussion of conditional handover", 3GPP DRAFT; R2-1814051 shows conditional handover signaling flow where multiple potential target cells may trigger the UE to send measurement report. SUMMARY This application provides a communication method and a communications apparatus. The method can improve a handover success rate. Appended claim 1 defines a communication method performed by a terminal device, or a chip in a terminal device Appended claim 8 defines a a terminal device, or a chip in a terminal device. Appended claim 9 defines a computer-readable storage medium. Appended claim 10 defines a communications system. The invention and its scope of protection is defined by these independent claims. The following aspects and implementations of the disclosure provide examples of combinations of technical subject matters. According to a first aspect, a communication method is provided. The method includes: A terminal device receives 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 currently accessed by the terminal device. The terminal device determines a first target cell based on the conditional handover configuration information. It should be understood that in this embodiment of this application, the conditional handover configuration information may be carried in a radio resource control (radio resource control, RRC) message. It should be understood that, in this embodiment of this application, "conditional handover" means that a specific condition needs to be satisfied when the terminal device performs a handover. To be specific, the condition may be referred to as a trigger condition of the handover performed by the terminal device. The terminal device may determine, based on signal quality of a serving cell and signal quality of a neighboring cell, the first target cell that satisfies the trigger condition. Optionally, after the terminal device determines the first target cell that satisfies the trigger condition, the method may further include: The terminal device performs a handover, that is, the terminal device is handed over from the serving cell to the first target cell. For example, the terminal device performs random access to the first target cell, to be handed over to the first target cell. In this embodiment of this application, the first network device sends the configuration information to the terminal device, so that the terminal device can determine a target cell based on the configuration information, and randomly access the determined target cell, to complete a handover procedure, thereby improving a handover success rate. It should be understood that the first target cell may be a neighboring cell of the serving cell. In this embodiment of this application, one network device may serve a plurality of cells. The handover in this embodiment of this application may be a handover in the serving cell, may be a handover between a plurality of cells served by one network device, or may be a cell handover between different network devices. This embodiment of this application is not limited thereto. Specifically, in this embodiment of this application, when the signal quality of the serving cell deteriorates, the terminal device may determine the target cell based on the conditional handover configuration information sent by the first network device. Compared with the current technology in which when signal quality of a current serving cell deteriorates, a network device sends a handover