Improved SINR Approximation for Downlink SDMA-based Networks with Outdated Channel State Information
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the proposed approximation in the context of Rate-Splitting Multiple Access (RSMA)-enabled MIMO DL systems with outdated CSIT.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.
Cite
@article{arxiv.2508.09020,
title = {Improved SINR Approximation for Downlink SDMA-based Networks with Outdated Channel State Information},
author = {Maria Cecilia Fernández Montefiore and Gustavo González and F. Javier López-Martínez and Fernando Gregorio},
journal= {arXiv preprint arXiv:2508.09020},
year = {2026}
}
Comments
5 pages, 3 figures. This work has been submitted to the IEEE for publication