CSI signaling for decentralized coordinated beamforming in TDD multi-cell MIMO systems

In this paper we present a novel multi-cell TDD CSI sounding concept for terminals employing multiple antennas. The objective is to support decentralized downlink beam coordination with minimal or no backhaul traffic between the base stations (BS). Each BS makes its own scheduling and precoding decisions independently, based on the locally available CSI and knowledge of the prior scheduling decisions made in the network. The concept combines interference-aware CSI sounding to busy signaling so that the sounding beams corresponding to the already allocated downlink data streams are considered as busy beams by the neighboring BSs. We experiment the concept in conjunction with simple regularized zero-forcing precoding and greedy beam scheduling.