An efficient downlink beamforming scheme for FDD/SDMA systems

Abstract

Without channel information of the downlink, the base station can generate downlink beam pattern using the weight vector used for the uplink. In the frequency division duplex system, however, it may result in significant performance degradation due to the carrier frequency offset between the uplink and downlink. To resolve this problem, we propose an efficient downlink beamforming algorithm based on a least square method with constraints. We also consider the control of null depth to obtain a desired signal to interference power ratio. Simulation results show that the proposed scheme can sufficiently reduce the interference from other users, improving the BER performance in the downlink.