A method, system, and device for downlink transmission. A downlink signal is sent to a UE in an available frequency band of an uplink frequency band, and no signal is sent or received in a guard frequency band of the uplink frequency band, where the guard frequency band is located in a highest-frequency part and/or a lowest-frequency part of the uplink frequency band. Because no signal is sent or received in the guard frequency band of the uplink frequency band, interference to communication of a UE in an adjacent frequency band is reduced when the uplink frequency band is occupied for downlink transmission, thereby improving system performance.