Practical RIS-Aided Multiuser Communications With Imperfect CSI: Practical Model, Amplitude Feedback, and Beamforming Optimization

Reconfigurable intelligent surfaces (RIS) can dynamically reconstruct wireless environments to enhance spectral efficiency. However, most existing studies have ignored the impact of the phase error and imperfect amplitude gain of the RIS. In this paper, we investigate the practical RIS-aided multius...

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Veröffentlicht in:IEEE transactions on wireless communications Jg. 23; H. 10; S. 15245 - 15260
Hauptverfasser: Zhang, Qian, Liu, Ju, Tang, Haoge, Dong, Zheng, Li, Yonghui
Format: Journal Article
Sprache:Englisch
Veröffentlicht: New York IEEE 01.10.2024
The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Schlagworte:
Algorithms
Amplitudes
Beamforming
beamforming optimization
Channel estimation
Closed form solutions
Communications systems
correlated channel
Couplings
Design optimization
Error analysis
Exact solutions
Feedback
low-complexity algorithm
Optimization
Optimization algorithms
Phase error
Phase shift
practical amplitude measurability
Practical reconfigurable intelligent surface (RIS)
Precoding
Quantization (signal)
Reconfigurable intelligent surfaces
surrogate expression
Wireless communication
ISSN:1536-1276, 1558-2248
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Zusammenfassung:Reconfigurable intelligent surfaces (RIS) can dynamically reconstruct wireless environments to enhance spectral efficiency. However, most existing studies have ignored the impact of the phase error and imperfect amplitude gain of the RIS. In this paper, we investigate the practical RIS-aided multiuser communication systems by maximizing the sum of users' average achievable rate, filling the current research gap. Specifically, a novel RIS phase shift design approach, namely amplitude feedback (AF), is proposed by utilizing the coupling relationship between the amplitude and phase to derive the optimal phase shift under the worst phase error. The feasibility of AF is demonstrated by proving the measurability of amplitude response through the electromagnetic theory. We propose a channel estimation design with low pilot overhead and provide an effective closed-form achievable rate to approximate the average achievable rate. Moreover, an efficient optimization algorithm is proposed to achieve the optimal closed-form precoding at the base station and the optimal trade-off design between the amplitude and phase of RIS, and the algorithm is extended to active RIS systems. Numerical results demonstrate that our proposed AF method and optimization algorithm can efficiently improve the performance in terms of achievable sum rate compared to existing methods.
Bibliographie:ObjectType-Article-1
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ISSN:1536-1276
1558-2248
DOI:10.1109/TWC.2024.3427695