Weight estimation for downlink null steering in a TDD/SDMA system

In employing an adaptive array for TDD/SDMA at a base station, generally, the array pattern for the downlink is calculated from that for the uplink. Considering the angle spread in a Rayleigh fading channel, the time difference between the uplink and downlink causes the null position change on the optimum array pattern. We propose a weight estimation method for the downlink null steering. It is based on the indirect weight estimation using the channel response prediction. The computer simulations show that the proposed method improves the BER performance in the downlink, effectively.