S307: The network device sends the to-be-monitored wake up signal to the terminal device based on the identifier of the terminal device.

Because the paging message received by the network device includes the identifier of the paged terminal device, after determining the to-be-monitored wake up signal in the plurality of wake up signals based on the first category and the grouping factor, the network device may determine the paged terminal device based on the identifier of the terminal device, and send the to-be-monitored wake up signal to the terminal device, to wake up the terminal device by using the to-be-monitored wake up signal.

S308: The terminal device monitors the to-be-monitored wake up signal.

After determining, in S304, the to-be-monitored wake up signal that needs to be monitored, the terminal device monitors a configuration of the to-be-monitored wake up signal to monitor the to-be-monitored wake up signal. Therefore, it can be learned that, compared with the current technology, according to the wake up signal sending method provided in this embodiment of this application, a group to which the terminal device belongs is not simply determined based on the identifier of the terminal device, but the service feature of the terminal device is considered, and the first category to which the terminal device belongs is determined based on the service feature of the terminal device. In this way, the to-be-monitored wake up signal may be determined in the plurality of wake up signals based on both the grouping factor and the first category that is corresponding to the service feature, so that a false alarm probability of paging is decreased, thereby reducing power consumption of a terminal device that is not paged.