In addition, it should be further noted that, because a process of classifying terminal devices based on service features is negotiated by the terminal device and the core network device, and is transparent to the network device, when the network device does not support classifying terminal devices based on service features, both the terminal device and the network device may determine the to-be-monitored signal in a fallback mechanism. In other words, reference may be made to a method in a current technology, to perform a modulo-N operation on identifiers of terminal devices, divide the terminal devices into groups based on remainders obtained after the modulo-N operation, and then determine the wake up signal that needs to wake up the terminal device, namely, a to-wake-up signal, based on a relationship between a group and a wake up signal. Alternatively, when the category information supported by the network device is less than categories negotiated by the terminal device and the core network device, for example, the category information negotiated by the terminal device and the core network device includes the high probability, the medium probability, and the low probability, but the network device supports only two categories: the medium probability and the low probability, the network device broadcasts, to a terminal device in a cell, a configuration of a plurality of wake up signals corresponding to the two types of wake up signals: the medium probability and the low probability, so that after receiving the configuration of the plurality of wake up signals that is broadcast by the network device, the terminal device determines the to-be-monitored wake up signal in the plurality of wake up signals based on the configuration, received by the terminal device, of the plurality of wake up signals corresponding to the two types of wake up signals: the medium probability and the low probability.