A communications system, comprising: a cellular base station, a millimeter wave base station, and user equipment, wherein the cellular base station is connected to the millimeter wave base station by using a transmission link, the cellular base station comprises a first cellular band transceiver, the millimeter wave base station comprises a second cellular band transceiver and a millimeter wave band transmitter, and the user equipment comprises a third cellular band transceiver and a millimeter wave band receiver, wherein the third cellular band transceiver is configured to receive control plane data information sent by the first cellular band transceiver or the second cellular band transceiver by using a cellular band; the third cellular band transceiver is further configured to send uplink data to the first cellular band transceiver or the second cellular band transceiver by using a cellular band; and the millimeter wave band receiver is configured to receive user plane data information sent by the millimeter wave band transmitter by using a millimeter wave band, wherein the cellular base station is further configured to allocate a first-bandwidth millimeter wave band to the user equipment, and the first cellular band transceiver is further configured to send first identification information of the first-bandwidth millimeter wave band to the third cellular band transceiver; or the millimeter wave base station is further configured to allocate a first-bandwidth millimeter wave band to the user equipment, and the second cellular band transceiver is further configured to send first identification information of the first-bandwidth millimeter wave band to the third cellular band transceiver; and the millimeter wave band receiver is further configured to receive, according to the first identification information, user plane data information sent by the millimeter wave band transmitter by using the first-bandwidth millimeter wave band, wherein the user equipment is configured to communicate with the cellular base station on a cellular band in a frequency division duplex, FDD, manner, and/or the user equipment is further configured to communicate with the millimeter wave base station on a cellular band in the FDD manner; the third cellular band transceiver is further configured to receive control plane data information sent by the first cellular band transceiver or the second cellular band transceiver by using a second-bandwidth cellular band; the third cellular band transceiver is further configured to send uplink data to the first cellular band transceiver or the second cellular band transceiver by using a third-bandwidth cellular band; characterized in that the cellular base station is further configured to increase, according to bandwidth of the first-bandwidth millimeter wave band and for the user equipment, specific bandwidth or a specific quantity of carriers for an uplink carrier of the third-bandwidth cellular band, and the first cellular band transceiver is further configured to send, to the third cellular band transceiver, second identification information of the third-bandwidth cellular band whose uplink carrier is increased; or the millimeter wave base station is further configured to increase, according to bandwidth of the first-bandwidth millimeter wave band and for the user equipment, specific bandwidth or a specific quantity of carriers for an uplink carrier of the third-bandwidth cellular band, and the second cellular band transceiver is further configured to send, to the third cellular band transceiver, second identification information of the third-bandwidth cellular band whose uplink carrier is increased; and the third cellular band transceiver is further configured to send, according to the second identification information, uplink data to the first cellular band transceiver or the second cellular band transceiver by using the third-bandwidth cellular band whose uplink carrier is increased.