Reconfigurable Intelligent Surface Assisted Multi-User Communications: How Many Reflective Elements Do We Need?
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TLDR
The asymptotic capacity with zero-forcing (ZF) precoding is derived, and how many reflective elements are required so that the ratio of the system sum-rate to the capacity can exceed a predefined threshold is analyzed.Abstract:
Reconfigurable intelligent surfaces (RISs) consisting of multiple reflective elements are a promising technique to enhance communication quality as they can create favorable propagation conditions. In this letter, we characterize the fundamental relations between the number of reflective elements and the system sum-rate in RIS-assisted multi-user communications. It is known from previous works that the received signal-to-noise ratio (SNR) can linearly increase with the squared number of RIS reflective elements, but how many elements are sufficient to provide an acceptable system sum-rate still remains an open problem. To this end, we derive the asymptotic capacity with zero-forcing (ZF) precoding, and then analyze how many reflective elements are required so that the ratio of the system sum-rate to the capacity can exceed a predefined threshold. Numerical results verify our analysis.read more
Citations
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Energy and Spectral Efficiency of Very Large Multiuser MIMO Systems
TL;DR: It is shown that the use of moderately large antenna arrays can improve the spectral and energy efficiency with orders of magnitude compared to a single-antenna system.
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Smart radio environments empowered by reconfigurable AI meta-surfaces: an idea whose time has come
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Wireless Communications With Reconfigurable Intelligent Surface: Path Loss Modeling and Experimental Measurement
Wankai Tang,Ming Zheng Chen,Xiangyu Chen,Jun Yan Dai,Yu Han,Marco Di Renzo,Yong Zeng,Shi Jin,Qiang Cheng,Tie Jun Cui +9 more
TL;DR: The proposed models, which are first validated through extensive simulation results, reveal the relationships between the free-space path loss of RIS-assisted wireless communications and the distances from the transmitter/receiver to the RIS, the size of the ris, the near-field/far-field effects of the RIS and the radiation patterns of antennas and unit cells.