Quantized Team Precoding: A Robust Approach for Network MIMO under General CSI Uncertainties

Abstract

The obtaining of accurate channel state information (CSI) at the transmitter (TX) side is known to be one of the main limitations for joint precoding across distant multiple-antennas TXs. Indeed, the knowledge of the multi-user CSI usually requires an information sharing step between the TXs, which makes cooperation challenging in many wireless settings. To alleviate the problem, we study the transmission when the CSI is imperfectly shared between the TXs, a setting we refer as Distributed D-CSIT. In such a case, the optimization of the joint precoder distributed across the distant TXs becomes a very different problem from the precoding usually encountered when all antennas receive the same channel estimate. Indeed, the precoder design then falls in the category of Team-Decision (TD) problems: Each TX does not know the information available (hence the precoder) at the other TXs. In this paper, we introduce a novel framework referred to as Quantized Team Precoding (QTP) which allows for robust distributed precoding in the presence of such CSI uncertainties.The methods relies on the concept of consistency enforcement, which is obtained by quantizing the CSI space. The obtained precoders exhibit superior rate performance compared to precoders that classical robust designs from the literature.