<p>Methods and apparatuses for calibrating antennas among multiple BS (Base Stations) s have been disclosed. A method for calibrating antennas between a first BS and a second BS is provided. The method comprises: obtaining UL (Uplink ) CSI (Channel State Information) of the first BS based on a SRS (Sounding Reference Signal) sent from a UE (User Equipment); obtaining UL equivalent CSI of the second BS via a weighted SRS sent from the UE. The weighted SRS is weighted with a ratio of DL (Downlink) CSI of the first BS to that of the second BS. The method further comprises calculating an ambiguity factor between the first BS and the second BS based on the UL CSI of the first BS and the UL equivalent CSI of the second BS. Then, the ambiguity factor may be used for calibrating the antenna between the two BSs.</p>
