Cooperative capacity-achieving precoding design for multi-user VFDM transmission

In this paper, we study cooperative precoder design in two-tier networks, consisting of a macro cell (MC) and small cells (SCs). By exploiting multi-user Vandermonde-subspace frequency division multiplexing (VFDM) transmission, a MC downlink can co-exist with cognitive SCs. In this paper, we first propose a cooperative cross-tier precoder (CTP) among the transmitters in the SCs to increase the transmit dimension. Moreover, the cooperative CTP allows us to use more efficient intra-tier precoder (ITP) in the SCs to handle intra-cell interference and improve the throughput of the cognitive system. And then, a capacity-achieving (CA) ITP is developed. Numerical results are presented to demonstrate the throughput improvement of the proposed scheme and the robustness to the channel estimation error.