Step 203a1: The terminal monitors the some or all second frequency resources in the N second frequency resources according to a fifth predetermined rule; and/or in this embodiment of the present disclosure, the foregoing step 203b specifically includes the following content:

Step 203b1: If the network device detects that X second frequency resources in the some or all second frequency resources are free, the network device selects at least one of the X second frequency resources as the target second frequency resource according to a sixth predetermined rule.

The fifth predetermined rule includes at least one of the following: second frequency resources satisfying a first condition are monitored, and a quantity of monitored second frequency resources is less than or equal to a sixth threshold; and the sixth predetermined rule includes at least one of the following: second frequency resources satisfying the first condition are selected, and a quantity of selected second frequency resources is less than or equal to a seventh threshold; where the first condition is that a frequency measurement value corresponding to the second frequency resource is greater than or equal to a second threshold.

For example, the fifth predetermined rule and the sixth predetermined rule are predefined or are configured by the network device for the terminal. This is not limited in the present disclosure.