Rate-Splitting Multiple Access (RSMA) is a robust multiple access scheme for multi-antenna wireless networks. In this work, we study the performance of RSMA in downlink overloaded networks, where the number of transmit antennas is smaller than the number of users. We provide analysis and closed-form solutions for optimal power and rate allocations that maximize max-min fairness when low-complexity precoding schemes are employed. The derived closed-form solutions are used to propose a low-complexity RSMA system design for precoder selection and resource allocation for arbitrary number of users and antennas under perfect and imperfect Channel State Information at the Transmitter (CSIT). We compare the performance of the proposed design with benchmark designs based on Space Division Multiple Access (SDMA) with and without user scheduling. By numerical results, we show that the proposed low-complexity RSMA design achieves a significantly higher rate compared to the SDMA-based benchmark designs under perfect and imperfect CSIT.

翻译：速率分割多址接入（RSMA）是一种用于多天线无线网络的鲁棒多址接入方案。本文研究了RSMA在下行过载网络中的性能，其中发射天线数量小于用户数量。我们针对采用低复杂度预编码方案时，实现最大-最小公平性的最优功率与速率分配进行了分析，并给出了闭式解。基于导出的闭式解，我们提出了一种低复杂度RSMA系统设计，用于在发送端信道状态信息（CSIT）完美与不完美情况下，针对任意用户与天线数量进行预编码器选择与资源分配。我们将所提设计的性能与基于空分多址接入（SDMA）的基准设计（含/不含用户调度）进行了对比。数值结果表明，在完美与不完美CSIT条件下，所提低复杂度RSMA设计相较于基于SDMA的基准设计实现了显著更高的速率。