# Two-Layer Decoding in Cellular Massive MIMO Systems with Spatial Channel Correlation

## TL;DR

This paper introduces a two-layer decoding approach for Massive MIMO systems that effectively reduces inter-cell interference through cooperative decoding and optimized power control, enhancing spectral efficiency.

## Contribution

It proposes a novel two-layer decoding scheme with a closed-form SE expression and an efficient algorithm for joint power and LSFD optimization in correlated Rayleigh fading channels.

## Key findings

- Closed-form spectral efficiency expression for the proposed scheme
- Effective joint optimization algorithm for power and LSFD vectors
- Significant interference mitigation and spectral efficiency improvement

## Abstract

This paper studies a two-layer decoding method that mitigates inter-cell interference in multi-cell Massive MIMO systems. In layer one, each base station (BS) estimates the channels to intra-cell users and uses the estimates 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, while a closed-form expression is obtained for correlated Rayleigh fading channels, maximum-ratio combining (MRC), and large-scale fading decoding (LSFD) in the second layer. We formulate a non-convex sum SE maximization problem with both the data power and LSFD vectors as optimization variables and develop an algorithm based on the weighted MMSE (minimum mean square error) approach to obtain a stationary point with low computational complexity.