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ZTE Communications ›› 2024, Vol. 22 ›› Issue (2): 99-106.DOI: 10.12142/ZTECOM.202402013

• Research Papers • 上一篇    

  

  • 收稿日期:2023-12-19 出版日期:2024-06-28 发布日期:2024-06-25

Cooperative Distributed Beamforming Design for Multi-RIS Aided Cell-Free Systems

ZHU Yuting1, XU Zhiyu2, ZHANG Hongtao1()   

  1. 1.Key Lab of Universal Wireless Communications, Ministry of Education of China, Beijing University of Posts and Telecommunications, Beijing 100876, China
    2.ZTE Corporation, Shenzhen 518057, China
  • Received:2023-12-19 Online:2024-06-28 Published:2024-06-25
  • About author:ZHU Yuting received her bachelor’s degree in communication engineering from the Beijing University of Posts and Telecommunications (BUPT), China in 2022. She is currently working toward her master's degree in communication and information engineering at the School of Artificial Intelligence, BUPT. Her research interests include the emerging technologies of 5G wireless communication network.
    XU Zhiyu received his PhD degree in electrical and electronic engineering from the Hong Kong University of Science and Technology (HKUST), China in 2002. He is currently a senior architect with ZTE Corporation, China. He has authored or coauthored more than 10 articles on international journals and conferences, and has filed more than 10 patents. He is the author of two technical books. His research interests include 6G wireless communication and signal processing.
    ZHANG Hongtao (htzhang@bupt.edu.cn) received his PhD degree in communication and information systems from the Beijing University of Posts and Telecommunications, China in 2008. He is currently a full professor with the Beijing University of Posts and Telecommunications, China. He has authored or coauthored more than 100 articles on international journals and conferences, and has filed more than 50 patents. He is the author of ten technical books. His research interests include 5G wireless communication and signal processing. He is a senior member of IEEE.

Abstract:

Cell-free systems significantly improve network capacity by enabling joint user service without cell boundaries, eliminating inter-cell interference. However, to satisfy further capacity demands, it leads to high-cost problems of both hardware and power consumption. In this paper, we investigate multiple reconfigurable intelligent surfaces (RISs) aided cell-free systems where RISs are introduced to improve spectrum efficiency in an energy-efficient way. To overcome the centralized high complexity and avoid frequent information exchanges, a cooperative distributed beamforming design is proposed to maximize the weighted sum-rate performance. In particular, the alternating optimization method is utilized with the distributed closed-form solution of active beamforming being derived locally at access points, and phase shifts are obtained centrally based on the Riemannian conjugate gradient (RCG) manifold method. Simulation results verify the effectiveness of the proposed design whose performance is comparable to the centralized scheme and show great superiority of the RISs-aided system over the conventional cellular and cell-free system.

Key words: cell-free systems, reconfigurable intelligent surface, cooperative distributed beamforming, Riemannian conjugate gradient