Joint Multiuser Random Beamforming and Zero-Forcing Precoding for SDMA Systems with Limited Feedback

Random beamforming (RBF) can obtain the same capacity scaling compared with the optimal precoding scheme in a sufficient number of users. However, the performance of RBF is decreased severely when with few users. In this letter, we propose a joint RBF and zero-forcing precoding scheme. Based on RBF, the initial scheduling is achieved, then these selected users are requested to feed back quantized channel direction information (CDI) and channel quality information (CQI). The base station accomplish the final beamforming by using zero-forcing precoding. Computer simulations are provided to evaluate the performance of the proposed schemes.