Coordinated multi-point transmission with non-ideal channel reciprocity

This paper studies robust transmission strategies for downlink time division duplex coordinated multi-point (CoMP) systems with non-ideal uplink-downlink channel reciprocity due to imperfect antenna calibration. By exploiting the statistics of antenna calibration errors, we first characterize the optimal parametric precoder structure that maximizes the weighted sum rate, based on which a closed-form robust signal-to-leakage-plus-noise ratio (RSLNR) precoder with properly selected parameters is then proposed. Simulation results show that the proposed precoder together with user scheduling provides near-optimal performance and data sharing among coordinated BSs may become detrimental depending on the employed precoders and the accuracy of antenna calibration.