Uplink signal structure design for multi-cell TDD massive MIMO systems

Abstract

For multi-cell time-division duplex (TDD) massive multiple-input multiple-output (MIMO) systems, pilot contamination originates from limited pilot resources has been proved to be the ultimate limiting factor when the base station (BS) antennas are increased without bound. In this paper, a modified uplink signal structure is proposed to reduce the negative effects of pilot contamination. Specifically, we add a certain amount of identification information for distinguishing the terminals in different cells at the beginning of uplink signals. With this improved uplink signal structure, the BS obtains better channel estimates. Then uplink signal-to-interference ratio (SIR) and available capacity are obviously increased. Further, we also analyze the performance of actual situation when errors occur during the transmission of identification information. Simulation results prove the effectiveness of this signal structure in obtaining better available capacity when the coherence interval is high.