Improved SINR Approximation for Downlink SDMA-based Networks with Outdated Channel State Information

TL;DR

This paper introduces an improved statistical model for SINR in downlink MU-MIMO systems with outdated CSIT, enhancing accuracy while maintaining simplicity, and validates it through extensive simulations.

Contribution

It proposes a new SINR approximation that overcomes limitations of existing models, providing more accurate performance analysis for MU-MIMO with imperfect CSIT.

Findings

The new approximation accurately models SINR variance.

It performs well across various system configurations.

The model is validated with RSMA-enabled MIMO systems.

Abstract

Understanding the performance of multi-user multiple-input multiple-output (MU-MIMO) systems under imperfect channel state information at the transmitter (CSIT) remains a critical challenge in next-generation wireless networks. In this context, accurate statistical modeling of the signal-to-interference-plus-noise ratio (SINR) is essential for enabling tractable performance analysis of multi-user systems. This paper presents an improved statistical approximation of the SINR for downlink (DL) MU-MIMO systems with imperfect CSIT. The proposed model retains the analytical simplicity of existing approaches (e.g., Gamma-based approximations) while overcoming their limitations, particularly the underestimation of SINR variance. We evaluate the proposed approximation in the context of Rate-Splitting Multiple Access (RSMA)-enabled MIMO DL systems with outdated CSIT. The results demonstrate excellent accuracy across a wide range of system configurations, including varying numbers of users, antennas, and degrees of CSIT staleness.