Beyond Massive-MIMO: The Potential of Data-Transmission with Large Intelligent Surfaces

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Abstract

In this paper, we consider the potential of data-transmission in a system with a massive number of radiating and sensing elements, thought of as a contiguous surface of electromagnetically active material. We refer to this as a Large Intelligent Surface (LIS). The "LIS" is a newly proposed concept, which conceptually goes beyond contemporary massive MIMO technology, and arises from our vision of a future where man-made structures are electronically active with integrated electronics and wireless communication making the entire environment "intelligent". Firstly, we consider capacities of single-antenna autonomous terminals communicating to the LIS where the entire surface is used as a receiving antenna-array in a perfect line-of-sight (LOS) propagation environment. Under the condition that the surface-area is sufficiently large, the received signal after a matched-filtering (MF) operation can be closely approximated by a sinc-function-like intersymbol interference (ISI) channel. Secondly, we analyze a normalized capacity measured per unit-surface, for a fixed transmit power per volume-unit with different terminal-deployments. As terminal-density increases, the limit of the normalized capacity [nats/s/Hz/volume-unit] achieved when wavelength <formula><tex>$\lambda$</tex></formula> approaches zero is equal to half of the transmit power per volume-unit divided by noise spatial power spectral density (PSD). Thirdly, we show that the number of independent signal dimensions that can be harvested per meter deployed surface is <formula><tex>$2/\lambda$</tex></formula> for one-dimensional terminal-deployment, and <formula><tex>$\pi/\lambda^{2}$</tex></formula> per square meter for two and three dimensional terminal-deployments. Lastly, we consider implementations of the LIS in the form of a grid of conventional antenna-elements, and show that the sampling lattice that minimizes the surface-area and simultaneously obtains one independent signal dimension for every spent antenna is the hexagonal lattice.

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Originalspråkengelska
Sidor (från-till)2746-2758
TidskriftIEEE Transactions on Signal Processing
Volym66
Utgåva nummer10
Tidigt onlinedatum2018 mar 16
StatusPublished - 2018 maj 15
PublikationskategoriForskning
Peer review utfördJa