Performances of beamforming in downlink with smart antenna testbed

This paper describes field trials with a smart antenna testbed system for IMT-2000 to evaluate the beamforming performance in the downlink. In the testbed system, a method to fit the transmit beam pattern to the virtual beam pattern, which is formed virtually for the downlink beamforming with correlation matrices measured in the uplink, was employed as the criterion of the downlink beamforming. Also, in consideration of the difference of antenna element radiation characteristics in uplink and downlink frequencies, the transmit and receive beam pattern calibration (TR-BPCal) algorithm was employed. The results of field trials confirmed the downlink beam/-steering to the desired/undesired user, the transmit power reduction in the base transceiver station due to the -steering to the interference signal and an improvement of the reduction when using the TR-BPCal algorithm.