One of the embodiments of the present invention relates to a method for rank adaptation at a base station. The method comprises performing, during a rank sounding time interval, data transmission for a user equipment by using a sounding rank. The sounding rank is different from a transmission rank that is used in a transmission time interval immediately prior to the rank sounding time interval. The method further comprises determining whether spectrum efficiency for the user equipment under the condition of using the sounding rank is better than spectrum efficiency under the condition of using the transmission rank; and adjusting, in response to a positive result obtained from the determining step, the transmission rank to the sounding rank so as to be used during a transmission time interval immediately next to the rank sounding time interval. The present invention also relates to corresponding base station device.