Rate-Splitting Multiple Access (RSMA) has recently appeared as a powerful and robust multiple access and interference management strategy for downlink Multi-user (MU) multi-antenna communications. In this work, we study the precoder design problem for RSMA scheme in downlink MU systems with both perfect and imperfect Channel State Information at the Transmitter (CSIT) and assess the role and benefits of transmitting multiple common streams. Unlike existing works which have considered single-antenna receivers (Multiple-Input Single-Output--MISO), we propose and extend the RSMA framework for multi-antenna receivers (Multiple-Input Multiple-Output--MIMO) and formulate the precoder optimization problem with the aim of maximizing the Weighted Ergodic Sum-Rate (WESR). Precoder optimization is solved using Sample Average Approximation (SAA) together with the proposed vectorization and Weighted Minimum Mean Square Error (WMMSE) based approach. Achievable sum-Degree of Freedom (DoF) of RSMA is derived for the proposed framework as an increasing function of the number of transmitted common and private streams, which is further validated by the Ergodic Sum Rate (ESR) performance using Monte Carlo simulations. Conventional MU-MIMO based on linear precoders and Non-Orthogonal Multiple Access (NOMA) schemes are considered as baselines. Numerical results show that with imperfect CSIT, the sum-DoF and ESR performance of RSMA is superior than that of the two baselines, and is increasing with the number of transmitted common streams. Moreover, by better managing the interference, RSMA not only has significant ESR gains over baseline schemes but is more robust to CSIT inaccuracies, network loads and user deployments.
翻译:快速跳动多端存取(RSMA)最近被看成是一个强大和强大的多端存取和干扰管理战略,用于下行多用户(MU)多层安非他明通信。在这项工作中,我们研究RSMA系统在下行系统与完美和不完善的传输器频道国家信息(CSIT)的频道状态信息(CSIT)系统下行链接中,预编码设计问题,评估传输器传输多种常见流的作用和好处。与考虑单端存接收器(Multiple-Input 单一输出-MISO)的现有工程不同,我们提议并扩展多端存接收器(MUMUMUM)的RSMA框架框架(MUMUM-MIM)的多端存存存存存存存存存存存和干涉(MIMA)框架(DoF)的多端存存存存存(MER),IMA(IMA IMA)的正常递转存取性运行(IMA-NLIMA)的平流(IMO-LIMO)计划由IMLIMLUU 的不断更新,由IMS-RLUU 的正常递增的运行(IMLI-LI)的运行的功能功能功能功能功能功能(由IMLLLLLLLLLLLLLL)的功能得到更进一步演算(由IMU)的更进一步演算,由IMLU),由IMLLLLLLLLU) 。