A communication system and method are provided. The communication system includes a master base station, a slave base station and a remote radio unit (RRU); where a cell controlled by the slave base station is included in cells controlled by the master base station. The master base station is configured to receive downlink data and send the downlink data to the slave base station; and the slave base station corresponds to a transmission channel identifier of the downlink data. The slave base station is configured to receive the downlink data sent by the master base station, convert the downlink data into air interface downlink vector data, and send the air interface downlink vector data to the RRU. The RRU is configured to convert the air interface downlink vector data into analog data and send the analog data to a user equipment, thereby realizing data transmission.