TY - JOUR
T1 - Beam Focusing for Near-Field Multiuser MIMO Communications
AU - Zhang, Haiyang
AU - Shlezinger, Nir
AU - Guidi, Francesco
AU - Dardari, Davide
AU - Imani, Mohammadreza F.
AU - Eldar, Yonina C.
N1 - Funding Information:
This work was supported in part by the European Union's H2020 Research and Innovation Program under Grant 101000967; in part by the Air Force Office of Scientific Research under Grant FA9550-18-1-0208; in part by the Israel Science Foundation under Grant 0100101; in part by the Theory Lab, Central Research Institute, 2012 Labs, Huawei Technologies Co., Ltd.; and in part by the Project Dipartimenti di Eccellenza-DEI, University of Bologna. An earlier version of this paper was in part at the 2021 IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP) [DOI: 10.1109/ICASSP39728.2021.9413746]. The associate editor coordinating the review of this article and approving it for publication was W. Ni.
Publisher Copyright:
© 2022 IEEE.
PY - 2022/9/1
Y1 - 2022/9/1
N2 - Large antenna arrays and high-frequency bands are two key features of future wireless communication systems. The combination of large-scale antennas with high transmission frequencies often results in the communicating devices operating in the near-field (Fresnel) region. In this paper, we study the potential of beam focusing, feasible in near-field operation, in facilitating high-rate multi-user downlink multiple-input multiple-output (MIMO) systems. As the ability to achieve beam focusing is dictated by the transmit antenna, we study near-field signalling considering different antenna structures, including fully-digital architectures, hybrid phase shifter-based precoders, and the emerging dynamic metasurface antenna (DMA) architecture for massive MIMO arrays. We first provide a mathematical model to characterize near-field wireless channels as well as the transmission pattern for the considered antenna architectures. Then, we formulate the beam focusing problem for the goal of maximizing the achievable sum-rate in multi-user networks. We propose efficient solutions based on the sum-rate maximization task for fully-digital, (phase shifters based-) hybrid and DMA architectures. Simulation results show the feasibility of the proposed beam focusing scheme for both single- and multi-user scenarios. In particular, the designed focused beams provide a new degree of freedom to mitigate interference in both angle and distance domains, which is not achievable using conventional far-field beam steering, allowing reliable communications for uses even residing at the same angular direction.
AB - Large antenna arrays and high-frequency bands are two key features of future wireless communication systems. The combination of large-scale antennas with high transmission frequencies often results in the communicating devices operating in the near-field (Fresnel) region. In this paper, we study the potential of beam focusing, feasible in near-field operation, in facilitating high-rate multi-user downlink multiple-input multiple-output (MIMO) systems. As the ability to achieve beam focusing is dictated by the transmit antenna, we study near-field signalling considering different antenna structures, including fully-digital architectures, hybrid phase shifter-based precoders, and the emerging dynamic metasurface antenna (DMA) architecture for massive MIMO arrays. We first provide a mathematical model to characterize near-field wireless channels as well as the transmission pattern for the considered antenna architectures. Then, we formulate the beam focusing problem for the goal of maximizing the achievable sum-rate in multi-user networks. We propose efficient solutions based on the sum-rate maximization task for fully-digital, (phase shifters based-) hybrid and DMA architectures. Simulation results show the feasibility of the proposed beam focusing scheme for both single- and multi-user scenarios. In particular, the designed focused beams provide a new degree of freedom to mitigate interference in both angle and distance domains, which is not achievable using conventional far-field beam steering, allowing reliable communications for uses even residing at the same angular direction.
KW - Beam focusing
KW - dynamic metasurface antennas
KW - near-field multi-user communication
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U2 - 10.1109/TWC.2022.3158894
DO - 10.1109/TWC.2022.3158894
M3 - Article
AN - SCOPUS:85126650337
SN - 1536-1276
VL - 21
SP - 7476
EP - 7490
JO - IEEE Transactions on Wireless Communications
JF - IEEE Transactions on Wireless Communications
IS - 9
ER -