Performance Analysis of Linear Precoders in TDD Massive MIMO Systems

I. A. QURESHI, S. ALI, F. KHUHAWAR

Abstract


The channel estimation of the reverse link and forward link in the massive multiple-input-multiple-output (M-MIMO) systems is projected using reverse link pilot training and channel reciprocity of time-division duplex (TDD) protocol, respectively. Nevertheless, the utilization of non-orthogonal reverse link pilot sequences in the neighboring cells, owing to limited coherence time causes pilot contamination that results in inter-cell interference in forward link data transmission. To design a TDD M-MIMO system properly under a practical multi-cell environment, it is necessary to evaluate the achievable rate of such systems. The performance assessment of multi-cell TDD M-MIMO forward-link system with linear precoders is proposed. The reverse-link and forward-link channels are first estimated by the BSs using least square channel estimator. Later, the closed-form approximate achievable forward-link sum-rate expressions of M-MIMO system with matched-filter (MF) and zero-forcing (ZF) precoders are derived. Finally, the performances of the achievable forward-link sum-rate for MF and ZF precoders are compared with respect to cell size, number of BS antennas, pilot length, and transmission SNR. Numerical simulation outcomes support the precision of closed-form rate expressions.

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