Multi-cell MMSE precoding in distributed antenna system with pilot contamination

Abstract

This paper studies the performance of downlink precoding in multi-cell multi-user large-scale distributed antenna system (DAS). Particularly, due to pilot reuse among users in adjacent cells, imperfect channel state information (CSI) is considered. Since the large scale fadings from different antennas to one user may be distinct from each other, it's difficult to jointly estimate the channels from all antennas to the users. Instead, this paper only jointly estimates the downlink channels of the antennas at the same site, thus with the same large scale fading. Based on the analysis of the properties of the estimated channels in large-scale DAS, we propose a multi-cell MMSE precoding scheme which aims to minimize the receiving signal error in one cell and the interference the cell pours to other cells. Simulation results show significant performance gains over traditional single-cell precoding schemes.