Rate Splitting Multiple Access in C-RAN: A Scalable and Robust Design
Rate Splitting Multiple Access in C-RAN: A Scalable and Robust Design
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DOI：
10.1109/tcomm.2021.3085343
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发表时间：
2020-10
影响因子：
8.3
通讯作者：
A. Ahmad;Yijie Mao;A. Sezgin;B. Clerckx
中科院分区：
文献类型：
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作者：
A. Ahmad;Yijie Mao;A. Sezgin;B. Clerckx
云无线电接入网络(C-RAN)为第五代通信网络(B5G)的超越提供了一个网络平台，它将云计算技术的进步融入到现代无线电接入网络中。近年来，速率分裂多址(RSMA)技术在发射端采用多天线速率分割(RS)，在接收端采用连续干扰消除(SIC)，可以有效地管理多天线通信网络中的干扰。本文考虑在C-RAN中应用RSMA。我们解决了发射机只知道用户的统计信道状态信息(CSI)的实际挑战。为此，本文研究了最大化网络遍历和速率(ESR)的随机协调波束形成(SCB)优化问题。此外，我们还提出了一种可扩展且稳健的RS方案，其中每个用户要解码的公共流的数量与用户数量成线性关系，并且公共流的选择仅依赖于统计的CSI。这种设置导致了一个具有挑战性的随机和非凸优化问题。采用基于样本平均逼近(SAA)和加权最小均方误差(WMMSE)的算法来处理难解的随机非凸优化问题，并保证渐近收敛到一个稳定点。数值仿真结果表明了该RS策略的有效性，并且与现有的将干扰视为噪声(TIN)和非正交多址(NOMA)方案相比，可实现的ESR提高了27%。
Cloud radio access networks (C-RAN) enable a network platform for beyond the fifth generation of communication networks (B5G), which incorporates the advances in cloud computing technologies to modern radio access networks. Recently, rate splitting multiple access (RSMA), relying on multi-antenna rate splitting (RS) at the transmitter and successive interference cancellation (SIC) at the receivers, has been shown to manage the interference in multi-antenna communication networks efficiently. This paper considers applying RSMA in C-RAN. We address the practical challenge of a transmitter that only knows the statistical channel state information (CSI) of the users. To this end, the paper investigates the problem of stochastic coordinated beamforming (SCB) optimization to maximize the ergodic sum-rate (ESR) in the network. Furthermore, we propose a scalable and robust RS scheme where the number of the common streams to be decoded at each user scales linearly with the number of users, and the common stream selection only depends on the statistical CSI. The setup leads to a challenging stochastic and non-convex optimization problem. A sample average approximation (SAA) and weighted minimum mean square error (WMMSE) based algorithm is adopted to tackle the intractable stochastic non-convex optimization and guarantee convergence to a stationary point asymptotically. The numerical simulations demonstrate the efficiency of the proposed RS strategy and show a gain up to 27% in the achievable ESR compared with state-of-the-art schemes, namely treating interference as noise (TIN) and non-orthogonal multiple access (NOMA) schemes.