A Fixed Group based Transmission Scheme with Limited Feedback in downlink Multiuser MIMO Systems

In downlink multiuser MIMO systems, multiuser interference (MUI) can be suppressed by ZF-precoding or BD methods. However, the quantization error in channel information feedback generates additional multiuser interference, which can't be suppressed by precoders. As a result, the performance is significantly degraded and exploitation of multiuser diversity is limited. In this paper, a fixed group based receiver multiuser interference cancelation scheme is proposed to eliminate such remained MUI. In this scheme, the codewords are separated into fixed groups, which is also known to users. In user scheduling, base station chooses the users with codewords in the same group. Therefore, the precoders used by interfering users is known, and the MUI generated by quantization error can be eliminated. The elimination can be performed by two schemes: decorrelation and MMSE scheme. The proposed scheme is compared with multiuser or single user ZF-precoding schemes by simulations. Numerical results show that the proposed scheme achieves significant performance improvement in terms of BER and throughput, and multiuser diversity can be fully exploited by choosing the best eigenmodes of each user.