This paper addresses the problem of channel estimation in a multiuser multi-cell wireless communications system in which the base station （BS） is equipped with a very large number of antennas （also referred to as"massive multiple-input multiple-output （MIMO）"）.We consider a time-division duplexing （TDD）scheme,in which reciprocity between the uplink and downlink channels can be assumed.Channel estimation is essential for downlink beamforming in massive MIMO,nevertheless,the pilot contamination effect hinders accurate channel estimation,which leads to overall performance degradation.Benefitted from the asymptotic orthogonality between signal and interference subspaces for non-overlapping angle-of arrivals （AOAs） in the large-scale antenna system,we propose a multiple signals classification （MUSIC） based channel estimation algorithm during the uplink transmission.Analytical and numerical results verify complete pilot decontamination and the effectiveness of the proposed channel estimation algorithm in the multiuser multi-cell massive MIMO system.
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