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Deep reinforcement learning for near-field wideband beamforming in STAR-RIS networks

基于深度强化学习的智能全向超表面辅助近场宽带通信系统波束赋形研究

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Abstract

A simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) assisted multiuser near-field wideband communication system is investigated, in which a robust deep reinforcement learning (DRL) based algorithm is proposed to enhance the users’ achievable rate by jointly optimizing the active beamforming at the base station (BS) and passive beamforming at the STAR-RIS. To mitigate the beam split issue, the delay-phase hybrid precoding structure is introduced to facilitate wideband beamforming. Considering the coupled nature of the STAR-RIS phase-shift model, the passive beamforming design is formulated as a problem of hybrid continuous and discrete phase-shift control, and the proposed algorithm controls the high-dimensional continuous action through hybrid action mapping. Additionally, to address the issue of biased estimation encountered by existing DRL algorithms, a softmax operator is introduced into the algorithm to mitigate this bias. Simulation results illustrate that the proposed algorithm outperforms existing algorithms and overcomes the issues of overestimation and underestimation.

摘要

本文研究了一种智能全向超表面辅助的多用户近场宽带通信系统, 提出了一种基于深度强化学习的鲁棒算法。通过联合优化基站的主动波束成形和智能全向超表面的被动波束成形, 提升用户的可达速率。为缓解宽带通信中的波束分裂问题, 引入了时相联合的混合预编码结构, 以实现高效的宽带波束成形。考虑到智能全向超表面相移模型的耦合性, 将无源波束成形设计转化为连续与离散相移的混合控制问题, 并通过混合动作映射解决高维连续动作的控制难题。此外, 针对现有深度强化学习算法中的估计偏差问题, 引入softmax算子有效减轻了该偏差。仿真结果表明, 所提算法在克服估计过高和估计过低问题方面优于现有算法。

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Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

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Authors and Affiliations

Authors

Contributions

Ji WANG designed the research. Jiayi SUN and Wei FANG processed the data. Ji WANG and Jiayi SUN drafted the paper. Zhao CHEN helped organize the paper. Zhao CHEN, Yue LIU, and Yuanwei LIU revised and finalized the paper.

Corresponding author

Correspondence to Zhao Chen  (陈钊).

Ethics declarations

Yuanwei LIU is a guest editor of this special issue, and he was not involved with the peer review process of this paper. All the authors declare that they have no conflict of interest.

Additional information

Project supported by the National Natural Science Foundation of China (Nos. 62101205 and 62101308) and the Key Research and Development Program of Hubei Province, China (No. 2023BAB061)

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Wang, J., Sun, J., Fang, W. et al. Deep reinforcement learning for near-field wideband beamforming in STAR-RIS networks. Front Inform Technol Electron Eng 25, 1651–1663 (2024). https://doi.org/10.1631/FITEE.2400364

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  • DOI: https://doi.org/10.1631/FITEE.2400364

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