Large-Scale-Fading Decoding in Cellular Massive MIMO Systems with Spatially Correlated Channels

TL;DR

This paper proposes a two-layer decoding method for multi-cell Massive MIMO systems that effectively mitigates intercell interference, improving spectral efficiency through optimized large-scale fading decoding and power control.

Contribution

It introduces a novel large-scale fading decoding scheme with a low-complexity optimization algorithm for interference mitigation in correlated Rayleigh fading environments.

Findings

Significant spectral efficiency gains with the proposed LSFD scheme.

Effective interference mitigation in correlated Rayleigh fading channels.

Enhanced performance through joint power control and LSFD optimization.

Abstract

Massive multiple-input--multiple-output (MIMO) systems can suffer from coherent intercell interference due to the phenomenon of pilot contamination. This paper investigates a two-layer decoding method that mitigates both coherent and non-coherent interference in multi-cell Massive MIMO. To this end, each base station (BS) first estimates the channels to intra-cell users using either minimum mean-squared error (MMSE) or element-wise MMSE (EW-MMSE) estimation based on uplink pilots. The estimates are used for local decoding on each BS followed by a second decoding layer where the BSs cooperate to mitigate inter-cell interference. An uplink achievable spectral efficiency (SE) expression is computed for arbitrary two-layer decoding schemes. A closed-form expression is then obtained for correlated Rayleigh fading, maximum-ratio combining, and the proposed large-scale fading decoding (LSFD) in the second layer. We also formulate a sum SE maximization problem with both the data power and LSFD vectors as optimization variables. Since this is an NP-hard problem, we develop a low-complexity algorithm based on the weighted MMSE approach to obtain a local optimum. The numerical results show that both data power control and LSFD improves the sum SE performance over single-layer decoding multi-cell Massive MIMO systems.