This application provides a communication method, apparatus, and system, to receive and send signals simultaneously through different bands, so as to reduce a communication delay. Specifically, a network device sends a first downlink signal to a terminal device through a downlink slot of a first band, and simultaneously, the network device receives a first uplink signal from the terminal device through an uplink slot of a second band, where there is an association relationship between an uplink-downlink slot configuration of the first band and an uplink-downlink slot configuration of the second band. In this application, a plurality of bands may share transmit and receive channel resources of the network device, to reduce costs and power consumption of the network device.