Improved SINR Approximation for Downlink RSMA-based Networks with Outdated Channel State Information
arXiv:2508.09020
The paper proposes a more accurate statistical approximation of the downlink SINR for multi‑user MIMO systems when the transmitter has outdated channel state information, and validates it for Rate‑Splitting Multiple Access scenarios.
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the proposed approximation in the context of Rate-Splitting Multiple Access (RSMA)-enabled MIMO DL systems with outdated CSIT.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.
6 pages, 3 figures. This work has been submitted to the IEEE for publication