Line-of-Sight and Pilot Contamination Effects on Correlated Multi-Cell Massive MIMO Systems

Abstract

This work considers the uplink (UL) of a multicell massive MIMO system with L cells, having each K monoantenna users communicating with an N −antennas base station (BS). The channel model involves Rician fading with distinct per-user Rician factors and channel correlation matrices and takes into account pilot contamination and imperfect CSI. The objective is to evaluate the performances of such systems with different single-cell and multi-cell detection methods. In the former, we investigate MRC and single-cell MMSE (S-MMSE); as to the latter, we are interested in multi-cell MMSE (M-MMSE) that was recently shown to provide unbounded rates in Rayleigh fading. The analysis is led assuming the infinite N limit and yields informative closed-form approximations that are substantiated by a selection of numerical results for finite system dimensions. Accordingly, these expressions are accurate and provide relevant insights into the effects of the different system parameters on the overall performances.

LMMSE Receivers in Uplink Massive MIMO Systems With Correlated Rician Fading

“…This latter admits the solution: κ ≥ tr Θ N T −τ τ . Finally, since the function T −τ τ is decreasing in τ , plus the fact that τ ∈ [K, T ), we can simply consider the lower bound given in (23), therefore concluding the proof. APPENDIX D PROOF OF THEOREM 4…”

On the Energy Efficiency of Multi-Cell Massive MIMO With Beamforming Training

“…However, in reality, a MIMO channel is generally correlated because the antennas are not sufficiently well separated or the propagation environment does not offer rich enough scattering. Considering the finite number of scattering clusters [22], recent papers study massive MIMO under a more realistic assumption of spatially correlated Rician fading [23]- [26]. Specifically, references [23] and [24] study performance of multi-cell massive MIMO systems and derive the statistical properties of the MMSE, element-wise MMSE (EM-MMSE), and least-square (LS) channel estimates when the BS uses MRC and MRT to perform UL detection and DL precoding, respectively.…”

“…Specifically, references [23] and [24] study performance of multi-cell massive MIMO systems and derive the statistical properties of the MMSE, element-wise MMSE (EM-MMSE), and least-square (LS) channel estimates when the BS uses MRC and MRT to perform UL detection and DL precoding, respectively. For other linear processing methods, such as multi-cell MMSE (MMMSE) and linear MMSE (LMMSE) processing, references [25] and [26] derive closedform asymptotic approximations of the UL spectral efficiency and show how the line-of-sight (LOS) components and pilot contamination affect the overall system performance in multicell UL massive MIMO systems.…”

“…Different from the majority of existing works, [13]- [15] consider the application of BT in a multi-cell massive MIMO system over Rayleigh or Rician fading channels. On the other hand, [23]- [26] examine the rate performance of a multicell massive MIMO system under spatially correlated Rician fading channels, but without BT. Given that there is only a limited amount of works on the application of BT for multicell massive MIMO systems over spatially correlated Rician fading channels, this paper shall carry out an extensive study on whether BT is beneficial to such systems.…”

“…Given that there is only a limited amount of works on the application of BT for multicell massive MIMO systems over spatially correlated Rician fading channels, this paper shall carry out an extensive study on whether BT is beneficial to such systems. While the works in [13]- [15] and [23]- [26] mainly focus on studying the system's spectral efficiency and do not consider EE, our paper also investigates the EE optimization problem for a multicell massive MIMO system over spatially correlated Rician fading channels with BT scheme. In summary, the main contributions of this paper are as follows:…”