TECHNICAL FIELD

Implementations of the present disclosure relate to the communication field, and more particularly, to a cell search method and a terminal device.

BACKGROUND

With people's pursuit of rate, latency, high-speed mobility and energy efficiency, and due to diversity and complexity of services in future life, International Standards Organization of 3rd Generation Partnership Project (3GPP) began to research and develop a 5-Generation mobile communication technology (5G). To reduce air interface signaling, quickly resume radio connection and quickly resume data service, a new Radio Resource Control (RRC) state, namely a radio resource control inactive (RRC_INACTIVE) state, is defined in a 5G network environment.

When a User Equipment (UE) is in the RRC_INACTIVE state, a network side configures a paging area of a Radio Access Network (RAN) for the UE. When the UE moves within the paging area, the network side is not notified, and a mobility behavior under RRC_IDLE, i.e., a cell selection and reselection principle, is followed. When the UE moves out of the paging area, the UE is triggered to resume a RRC connection and re-obtain a paging area configured by the network side.

When a cell signal is not good, the UE in the INACTIVE state may be unable to find a suitable cell to reside in, and the UE may enter an arbitrary cell search state or may choose an acceptable cell to reside in. It can be found that how to control a state and context of the UE and how to ensure that a UE's behavior is manageable and controllable is an urgent problem to be solved.

SUMMARY

A cell search method and a terminal device are provided.

In a first aspect, a cell search method is provided, which is applied to a terminal device in an inactive state, wherein the inactive state refers to that the terminal device is disconnected from a network device, and both the network device and the terminal device retain context information of the terminal device, wherein the context information is used for establishing a connection between the terminal device and the network device; the method includes that the terminal device enters an arbitrary cell search state to search for an acceptable cell and/or a suitable cell when the terminal device does not search out any suitable cell to reside in, wherein the acceptable cell is a cell in which the terminal device is capable of residing and only obtaining a restricted service, and the suitable cell is a cell in which the terminal device is capable of residing and obtaining a normal service.

In an embodiment of the present invention, when no suitable cell is searched out to reside in by a terminal device in the INACTIVE state, the terminal device searches for an acceptable cell and/or a suitable cell by entering an arbitrary cell search state.

In some possible implementations, the method further includes that when searching out the acceptable cell, the terminal device resides in the acceptable cell and continues to search for the suitable cell.

In some possible implementations, the method further includes that when entering the arbitrary cell search state, the terminal device starts a first timer; when the first timer expires and no suitable cell is searched out, the terminal device enters an idle state and deletes the context information; and when the first timer does not expire and the suitable cell is searched out, the terminal device stops the first timer and resides in the suitable cell.

In some possible implementations, before the terminal device starts the first timer, the method further includes that the terminal device receives configuration information sent by the network device, wherein the configuration information is used for the terminal device to configure the first timer.

In some possible implementations, the configuration information is information configured for the terminal device when the network device instructs the terminal device to enter the inactive state.

In some possible implementations, the method further includes that when entering the arbitrary cell search state, the terminal device enters the idle state and deletes the context information.

In some possible implementations, the method further includes that when entering the arbitrary cell search state, the terminal device continues to maintain the inactive state and a second timer, wherein the second timer includes a location update timer.

In some possible implementations, the method further includes that when the second timer expires, the terminal device enters the idle state and deletes the context information.

In some possible implementations, the method further includes that after entering the idle state and deleting the context information, the terminal device continues to maintain the arbitrary cell search state.

In the embodiment of the present invention, when no suitable cell is searched out to reside in by the terminal device in the INACTIVE state, the terminal device searches for an acceptable cell and/or a suitable cell by entering an arbitrary cell search state.

In a second aspect, a terminal device is provided, wherein the terminal device is in an inactive state, the inactive state refers to that the terminal device is disconnected from a network device, and both the network device and the terminal device retain context information of the terminal device, the context information is used for establishing a connection between the terminal device and the network device; the terminal device includes a processing unit.

Herein, the processing unit is configured to enter an arbitrary cell search state to search for an acceptable cell and/or a suitable cell when the terminal device does not search out any suitable cell to reside in, wherein the acceptable cell is a cell in which the terminal device is capable of residing and only obtaining a restricted service, and the suitable cell is a cell in which the terminal device is capable of residing and obtaining a normal service.

In a third aspect, a terminal device is provided, wherein the terminal device is in an inactive state, the inactive state refers to that the terminal device is disconnected from a network device, and both the network device and the terminal device retain context information of the terminal device, the context information is used for establishing a connection between the terminal device and the network device; the terminal device includes a processor.

Herein, the processor is configured to enter an arbitrary cell search state to search for an acceptable cell and/or a suitable cell when the terminal device does not search out any suitable cell to reside in, wherein the acceptable cell is a cell in which the terminal device is capable of residing and only obtaining a restricted service, and the suitable cell is a cell in which the terminal device is capable of residing and obtaining a normal service.

In a fourth aspect, a computer readable medium is provided for storing a computer program thereon. The computer program includes instructions used for performing the method implementation of the above first aspect.

In a fifth aspect, a computer chip is provided. The computer chip includes an input interface, an output interface, at least one processor, and a memory. The at least one processor is used for executing codes in the memory. When the codes are executed, the processor may implement various processes executed by the terminal device in the cell search method of the above first aspect and various implementations.

In a sixth aspect, a communication system is provided, which includes the above terminal device.

