Zero-Forcing Beamforming with Semiorthogonal User Selection Modified for Reducing Feedback Information

In this paper, we propose a modified version of zero- forcing beamforming with semiorthogonal user selection (SUS) (ZFBF with mSUS) which will dramatically reduced the feedback load compared with the original one. In ZFBF with mSUS, the base station requires the channel state information (CSI) only from the users who have larger SNR than a predefined threshold. Adjusting the threshold changes the amount of feedback as well as the throughput. We show that the performance of this modified version is also asymptotically close to that of dirty paper coding (DPC). With numerical investigation, the feedback load is shown to be greatly reduced. Although the proposed method achieves slightly lower throughput than that of ZFBF with SITS especially for a small number of users since we do not optimize algorithm parameters in the simulation, the performance gap quickly vanishes as the number of users becomes large.