Cooperative Precoding and Beamforming for Co-Existing Multi-User MIMO Systems

Interference among multiple base stations that co-exist in the same location limits the capacity of wireless networks. In this paper, we propose a nonlinear multi-user MIMO cooperative downlink transmission scheme. The algorithm eliminates the interference and achieves symbol error rate (SER) fairness among different users. To eliminate the interference, Tomlinson Harashima precoding (THP) is used to cancel part of the interference while the transmit-receive antenna weights cancel the remaining part. The uplink-downlink duality principle is used to calculate transmit-receive antenna weights. The proposed scheme is then extended to work when the receiver does not have complete Channel State Informations (CSIs). The simulation results show that the proposed schemes considerably outperform existing cooperative transmission schemes in terms of SER performance and approach an interference free performance under the same configuration.