A communications apparatus. The RF signal processing device is capable of supporting carrier aggregation and configured to process RF signals. The baseband signal processing device is configured to process baseband signals. The processor is configured to control operations of the RF signal processing device and the baseband signal processing device. The processor further receives a power control signal from a peer communications apparatus, obtains an assigned transmission power which is assigned by the peer communications apparatus for the communications apparatus to transmit a reference signal according to information carried in the power control signal, determines a spectral efficiency estimation value of the communications apparatus and directs the RF signal processing device to transmit the reference signal with a reduced transmission power which is smaller than the assigned transmission power when the spectral efficiency estimation value is smaller than a predetermined threshold.