用机器学习预测大规模天线非线性干扰,提升用户吞吐量12%。
Impact of Nonlinear Power Amplifier on Massive MIMO: Machine Learning Prediction Under Realistic Radio Channel

- 基于3D射线追踪数据构建机器学习模型,预测用户接收的信号失真比。
- 相比传统方案,新方法在真实信道下实现12%的中位数吞吐量增益。
- 适合关注6G高效功放设计与智能资源分配的研究者。
大规模多输入多输出(M-MIMO)是提升无线网络频谱与能效的关键技术。现有研究多假设天线阵列采用线性前端,但为追求更高能效,硬件工作于非线性区域,尤其在高均峰比的多载波系统(如4G/5G/6G中的OFDM)中更为显著。虽然非线性功率放大器(PA)对OFDM信号的影响已有研究,但在M-MIMO系统中的影响仍属新兴课题。多数现有工作忽略非线性效应或依赖适用于瑞利/直视信道的简化模型。本文首先理论上分析了常用信道模型下的非线性失真;随后通过3D射线追踪(3D-RT)软件验证这些模型精度不足。为此,提出两种新模型:一种基于广义极值分布(GEV)的统计模型,用于建模受害用户接收到的信号失真比(SDR);另一种基于机器学习的模型,根据信道空间特性与各天线支路功放的工作点,预测调度用户所受的总失真比。该预测结果可用于实现面向功放的用户级功率分配。实验表明,相比现有固定工作点方案,所提基于机器学习的功率分配方案可实现约12%的中位数用户吞吐量提升。
原文摘要 · Abstract (English)
M-MIMO is one of the crucial technologies for increasing spectral and energy efficiency of wireless networks. Most of the current works assume that M-MIMO arrays are equipped with a linear front end. However, ongoing efforts to make wireless networks more energy-efficient push the hardware to the limits, where its nonlinear behavior appears. This is especially a common problem for the multicarrier systems, e.g., OFDM used in 4G, 5G, and possibly also in 6G, which is characterized by a high Peak-to-Average Power Ratio. While the impact of a nonlinear Power Amplifier (PA) on an OFDM signal is well characterized, it is a relatively new topic for the M-MIMO OFDM systems. Most of the recent works either neglect nonlinear effects or utilize simplified models proper for Rayleigh or LoS radio channel models. In this paper, we first theoretically characterize the nonlinear distortion in the M-MIMO system under commonly used radio channel models. Then, utilizing 3D-Ray Tracing (3D-RT) software, we demonstrate that these models are not very accurate. Instead, we propose two models: a statistical one and an ML-based one using 3D-RT results. The proposed statistical model utilizes the Generalized Extreme Value (GEV) distribution to model Signal to Distortion Ratio (SDR) for victim users, receiving nonlinear distortion, e.g., as interference from neighboring cells. The proposed ML model aims to predict SDR for a scheduled user (receiving nonlinear distortion along with the desired signal), based on the spatial characteristics of the radio channel and the operation point of each PA feeding at the M-MIMO antenna array. The predicted SDR can then be used to perform PA-aware per-user power allocation. The results show about 12% median gain in user throughput achieved by the proposed ML-based power allocation scheme over the state-of-the-art, fixed operating point scheme.
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