A base station (BS) for sharing downlink (DL) demodulation reference signals (DMRSs) between the DL data and the DL control signals comprises a storage device for storing instructions and a processing circuit coupled to the storage device. The processing circuit is configured to execute the instructions stored in the storage device. The instructions comprise transmitting a DL control signal on a first layer in a first time-frequency resource to the communication device; transmitting a DL data, associated with the DL control signal on a second layer in the first time-frequency resource and on the first layer and the second layer in a second time-frequency resource, to the communication device; and transmitting a set of DMRSs for the DL control signal and the DL data to the communication device.