Cooperative Precoding and Beamforming in Co-Working WLANs

The interference among multiple access points (APs) that co-exist in the same location, limits the capacity of co-working wireless local area networks (WLANs). In this paper, we propose a practical cooperative transmission scheme to mitigate the interference in co-working WLANs. In particular, we combine Tomlinson Harashima precoding (THP), joint transmit-receive beamforming based on SINR (signal-to-interference-plus-noise-ratio) maximization, and an adaptive precoding order to eliminate co-working interference and achieve bit error rate (BER) fairness among different users. We consider the design of the system when partial channel state information (CSI) (where each user only knows its own CSI) and full CSI (where each user knows CSI of all users) are available at the receiver respectively. We prove analytically and by simulation that the performance of our proposed scheme will not be degraded under partial CSI. The simulation results show that the proposed scheme considerably outperforms both the existing non-cooperative and cooperative transmission schemes and is only 2 dB away from an interference-free channel under the same configuration.