A first terminal obtains a first transmission resource that is sent by an access network device and that is used by the first terminal to send data on a sidelink, where the sidelink is a wireless communication link between the first terminal and a second terminal, and the first transmission resource is a resource of an unlicensed spectrum. The first terminal performs a channel access procedure on the unlicensed spectrum. The first terminal sends first information to the access network device when the first terminal determines that a failure occurs in the channel access procedure performed on the unlicensed spectrum, where the first information is used to request to allocate a second transmission resource to the sidelink of the unlicensed spectrum.