这份研究论文提出了一种高效的波束成形优化框架，用于在信道状态信息不完美的情况下最大化广义速率分层多址接入（GRS）的遍历和速率（ESR）。作者通过样本平均近似（SAA）将随机问题转化为确定性问题，并利用分数规划（FP）方法将其分解为一系列凸子问题。论文的核心贡献在于推导了GRS的最优波束成形结构（OBS），并开发了基于超平面不动点迭代（HFPI）的方法来计算拉格朗日对偶变量，从而无需使用传统的优化工具箱。研究结果表明，所提出的算法显著降低了计算复杂性，同时保持了与现有方法相同的ESR性能，并首次展示了GRS在多用户场景下的表现，凸显了其在未来6G网络中提高频谱效率的潜力。

An Efficient Beamforming Optimization Framework for Generalized Rate-Splitting with Imperfect CSIT

Abstract:

Rate-splitting multiple access (RSMA) emerges as a compelling physical-layer transmission paradigm for effectively managing interference in 6G networks. Within the realm of RSMA transmission frameworks, generalized rate-splitting (GRS) stands out as a versatile strategy that embraces existing multiple access (MA) schemes, including space division multiple access (SDMA), non-orthogonal multiple access (NOMA), and orthogonal multiple access (OMA) as specific instances. Despite its versatility, GRS encounters significant design challenges, particularly in dealing with the resource optimization complexities resulting from the exponential growth in the number of common streams with the number of users. To tackle the issue, in this work, we propose a novel and highly efficient beamforming optimization algorithm for GRS to maximize the ergodic sum rate (ESR) with imperfect channel state information at the transmitter (CSIT). Specifically, the stochastic ESR maximization problem is first transformed into a deterministic one using sampled average approximation (SAA). This transformed problem is further decomposed into a series of convex subproblems by the fraction programming (FP) approach. Based on the Karush-Kuhn-Tucker (KKT) conditions of each subproblem, we derive the optimal beamforming structure (OBS) of GRS. To determine the Lagrange dual variables within the OBS, we then propose a fixed point iteration (FPI)-based method. Through extensive numerical results, we show that the proposed algorithm significantly reduces the computational complexity without sacrificing ESR performance compared to conventional optimization algorithms. Thanks to the efficiency of our algorithm, we illustrate, for the first time, the performance of GRS with more than three users. We draw the conclusion that our proposed algorithm shows promise in advancing the practical application of RSMA in 6G.

Published in: IEEE Transactions on Communications ( Early Access )

Page(s): 1 - 1

Date of Publication: 24 March 2025

ISSN Information:

Print ISSN: 0090-6778

Electronic ISSN: 1558-0857

DOI: 10.1109/TCOMM.2025.3552748

Publisher: IEEE

Funding Agency:

10.13039/501100005153-China National Funds for Distinguished Young Scientists (Grant Number: 62201347)